CSY/reowolf Changeset - f34349cabe17 · Centrum Wiskunde & Informatica (CWI)

Changeset - f34349cabe17

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MH - 3 years ago 2022-02-25 11:54:59
contact@maxhenger.nl

WIP: Fix bug related to builtin procedure typechecking

3 files changed with 28 insertions and 17 deletions:

src/protocol/parser/mod.rs

src/protocol/parser/pass_typing.rs

src/protocol/parser/type_table.rs

0 comments (0 inline, 0 general)

src/protocol/parser/mod.rs

➞

Show inline comments

 #[macro_use] mod visitor;
 pub(crate) mod symbol_table;
 pub(crate) mod type_table;
 pub(crate) mod tokens;
 pub(crate) mod token_parsing;
 pub(crate) mod pass_tokenizer;
 pub(crate) mod pass_symbols;
 pub(crate) mod pass_imports;
 pub(crate) mod pass_definitions;
 pub(crate) mod pass_definitions_types;
 pub(crate) mod pass_validation_linking;
 pub(crate) mod pass_rewriting;
 pub(crate) mod pass_typing;
 pub(crate) mod pass_stack_size;
 use tokens::*;
 use crate::collections::*;
 use visitor::Visitor;
 use pass_tokenizer::PassTokenizer;
 use pass_symbols::PassSymbols;
 use pass_imports::PassImport;
 use pass_definitions::PassDefinitions;
 use pass_validation_linking::PassValidationLinking;
 use pass_typing::{PassTyping, ResolveQueue};
 use pass_rewriting::PassRewriting;
 use pass_stack_size::PassStackSize;
 use symbol_table::*;
 use type_table::*;
 use crate::protocol::ast::*;
 use crate::protocol::input_source::*;
 use crate::protocol::ast_printer::ASTWriter;
 use crate::protocol::parser::type_table::PolymorphicVariable;
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
 pub enum ModuleCompilationPhase {
     Tokenized,              // source is tokenized
     SymbolsScanned,         // all definitions are linked to their type class
     ImportsResolved,        // all imports are added to the symbol table
     DefinitionsParsed,      // produced the AST for the entire module
     TypesAddedToTable,      // added all definitions to the type table
     ValidatedAndLinked,     // AST is traversed and has linked the required AST nodes
     Typed,                  // Type inference and checking has been performed
     Rewritten,              // Special AST nodes are rewritten into regular AST nodes
     // When we continue with the compiler:
     // StackSize
+}
 pub struct Module {
     // Buffers
     pub source: InputSource,
     pub tokens: TokenBuffer,
     // Identifiers
     pub root_id: RootId,
     pub name: Option<(PragmaId, StringRef<'static>)>,
     pub version: Option<(PragmaId, i64)>,
     pub phase: ModuleCompilationPhase,
+}
 pub struct TargetArch {
     pub void_type_id: TypeId,
     pub message_type_id: TypeId,
     pub bool_type_id: TypeId,
     pub uint8_type_id: TypeId,
     pub uint16_type_id: TypeId,
     pub uint32_type_id: TypeId,
     pub uint64_type_id: TypeId,
     pub sint8_type_id: TypeId,
     pub sint16_type_id: TypeId,
     pub sint32_type_id: TypeId,
     pub sint64_type_id: TypeId,
     pub char_type_id: TypeId,
     pub string_type_id: TypeId,
     pub array_type_id: TypeId,
     pub slice_type_id: TypeId,
     pub input_type_id: TypeId,
     pub output_type_id: TypeId,
     pub pointer_type_id: TypeId,
+}
 impl TargetArch {
     fn new() -> Self {
         return Self{
             void_type_id: TypeId::new_invalid(),
             bool_type_id: TypeId::new_invalid(),
             message_type_id: TypeId::new_invalid(),
             uint8_type_id: TypeId::new_invalid(),
             uint16_type_id: TypeId::new_invalid(),
             uint32_type_id: TypeId::new_invalid(),
             uint64_type_id: TypeId::new_invalid(),
             sint8_type_id: TypeId::new_invalid(),
             sint16_type_id: TypeId::new_invalid(),
             sint32_type_id: TypeId::new_invalid(),
             sint64_type_id: TypeId::new_invalid(),
             char_type_id: TypeId::new_invalid(),
             string_type_id: TypeId::new_invalid(),
             array_type_id: TypeId::new_invalid(),
             slice_type_id: TypeId::new_invalid(),
             input_type_id: TypeId::new_invalid(),
             output_type_id: TypeId::new_invalid(),
             pointer_type_id: TypeId::new_invalid(),
+        }
+    }
+}
 pub struct PassCtx<'a> {
     heap: &'a mut Heap,
     symbols: &'a mut SymbolTable,
     pool: &'a mut StringPool,
     arch: &'a TargetArch,
+}
 pub struct Parser {
     // Storage of all information created/gathered during compilation.
     pub(crate) heap: Heap,
     pub(crate) string_pool: StringPool, // Do not deallocate, holds all strings
     pub(crate) modules: Vec<Module>,
     pub(crate) symbol_table: SymbolTable,
     pub(crate) type_table: TypeTable,
     // Compiler passes, used as little state machine that keep their memory
     // around.
     pass_tokenizer: PassTokenizer,
     pass_symbols: PassSymbols,
     pass_import: PassImport,
     pass_definitions: PassDefinitions,
     pass_validation: PassValidationLinking,
     pass_typing: PassTyping,
     pass_rewriting: PassRewriting,
     pass_stack_size: PassStackSize,
     // Compiler options
     pub write_ast_to: Option<String>,
     pub(crate) arch: TargetArch,
+}
 impl Parser {
     pub fn new() -> Self {
         let mut parser = Parser{
             heap: Heap::new(),
             string_pool: StringPool::new(),
             modules: Vec::new(),
             symbol_table: SymbolTable::new(),
             type_table: TypeTable::new(),
             pass_tokenizer: PassTokenizer::new(),
             pass_symbols: PassSymbols::new(),
             pass_import: PassImport::new(),
             pass_definitions: PassDefinitions::new(),
             pass_validation: PassValidationLinking::new(),
             pass_typing: PassTyping::new(),
             pass_rewriting: PassRewriting::new(),
             pass_stack_size: PassStackSize::new(),
             write_ast_to: None,
             arch: TargetArch::new(),
         };
         parser.symbol_table.insert_scope(None, SymbolScope::Global);
         // Insert builtin types
         // TODO: At some point use correct values for size/alignment
         parser.arch.void_type_id    = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::Void], false, 0, 1);
         parser.arch.message_type_id = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::Message], false, 24, 8);
         parser.arch.bool_type_id    = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::Bool], false, 1, 1);
         parser.arch.uint8_type_id   = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::UInt8], false, 1, 1);
         parser.arch.uint16_type_id  = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::UInt16], false, 2, 2);
         parser.arch.uint32_type_id  = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::UInt32], false, 4, 4);
         parser.arch.uint64_type_id  = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::UInt64], false, 8, 8);
         parser.arch.sint8_type_id   = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::SInt8], false, 1, 1);
         parser.arch.sint16_type_id  = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::SInt16], false, 2, 2);
         parser.arch.sint32_type_id  = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::SInt32], false, 4, 4);
         parser.arch.sint64_type_id  = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::SInt64], false, 8, 8);
         parser.arch.char_type_id    = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::Character], false, 4, 4);
         parser.arch.string_type_id  = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::String], false, 24, 8);
         parser.arch.array_type_id   = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::Array, ConcreteTypePart::Void], true, 24, 8);
         parser.arch.slice_type_id   = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::Slice, ConcreteTypePart::Void], true, 16, 4);
         parser.arch.input_type_id   = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::Input, ConcreteTypePart::Void], true, 8, 8);
         parser.arch.output_type_id  = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::Output, ConcreteTypePart::Void], true, 8, 8);
         parser.arch.pointer_type_id = insert_builtin_type(&mut parser.type_table, vec![ConcreteTypePart::Pointer, ConcreteTypePart::Void], true, 8, 8);
         // Insert builtin functions
         fn quick_type(variants: &[ParserTypeVariant]) -> ParserType {
             let mut t = ParserType{ elements: Vec::with_capacity(variants.len()), full_span: InputSpan::new() };
             for variant in variants {
                 t.elements.push(ParserTypeElement{ element_span: InputSpan::new(), variant: variant.clone() });
+            }
+            t
+        }
         use ParserTypeVariant as PTV;
         insert_builtin_function(&mut parser, "get", &["T"], |id| (
             vec![
                 ("input", quick_type(&[PTV::Input, PTV::PolymorphicArgument(id.upcast(), 0)]))
             ],
             quick_type(&[PTV::PolymorphicArgument(id.upcast(), 0)])
         ));
         insert_builtin_function(&mut parser, "put", &["T"], |id| (
             vec![
                 ("output", quick_type(&[PTV::Output, PTV::PolymorphicArgument(id.upcast(), 0)])),
                 ("value", quick_type(&[PTV::PolymorphicArgument(id.upcast(), 0)])),
             ],
             quick_type(&[PTV::Void])
         ));
         insert_builtin_function(&mut parser, "fires", &["T"], |id| (
             vec![
                 ("port", quick_type(&[PTV::InputOrOutput, PTV::PolymorphicArgument(id.upcast(), 0)]))
             ],
             quick_type(&[PTV::Bool])
         ));
         insert_builtin_function(&mut parser, "create", &["T"], |id| (
             vec![
                 ("length", quick_type(&[PTV::IntegerLike]))
             ],
             quick_type(&[PTV::ArrayLike, PTV::PolymorphicArgument(id.upcast(), 0)])
         ));
         insert_builtin_function(&mut parser, "length", &["T"], |id| (
             vec![
                 ("array", quick_type(&[PTV::ArrayLike, PTV::PolymorphicArgument(id.upcast(), 0)]))
             ],
             quick_type(&[PTV::UInt32]) // TODO: @PtrInt
         ));
         insert_builtin_function(&mut parser, "assert", &[], |_id| (
             vec![
                 ("condition", quick_type(&[PTV::Bool])),
             ],
             quick_type(&[PTV::Void])
         ));
         insert_builtin_function(&mut parser, "print", &[], |_id| (
             vec![
                 ("message", quick_type(&[PTV::String])),
             ],
             quick_type(&[PTV::Void])
         ));
         parser
+    }
     pub fn feed(&mut self, mut source: InputSource) -> Result<(), ParseError> {
         let mut token_buffer = TokenBuffer::new();
         self.pass_tokenizer.tokenize(&mut source, &mut token_buffer)?;
         let module = Module{
             source,
             tokens: token_buffer,
             root_id: RootId::new_invalid(),
             name: None,
             version: None,
             phase: ModuleCompilationPhase::Tokenized,
         };
         self.modules.push(module);
         Ok(())
+    }
     pub fn parse(&mut self) -> Result<(), ParseError> {
         let mut pass_ctx = PassCtx{
             heap: &mut self.heap,
             symbols: &mut self.symbol_table,
             pool: &mut self.string_pool,
             arch: &self.arch,
         };
         // Advance all modules to the phase where all symbols are scanned
         for module_idx in 0..self.modules.len() {
             self.pass_symbols.parse(&mut self.modules, module_idx, &mut pass_ctx)?;
+        }
         // With all symbols scanned, perform further compilation until we can
         // add all base types to the type table.
         for module_idx in 0..self.modules.len() {
             self.pass_import.parse(&mut self.modules, module_idx, &mut pass_ctx)?;
             self.pass_definitions.parse(&mut self.modules, module_idx, &mut pass_ctx)?;
+        }
         // Add every known type to the type table
         self.type_table.build_base_types(&mut self.modules, &mut pass_ctx)?;
         // Continue compilation with the remaining phases now that the types
         // are all in the type table
         for module_idx in 0..self.modules.len() {
             let mut ctx = visitor::Ctx{
                 heap: &mut self.heap,
                 modules: &mut self.modules,
                 module_idx,
                 symbols: &mut self.symbol_table,
                 types: &mut self.type_table,
                 arch: &self.arch,
             };
             self.pass_validation.visit_module(&mut ctx)?;
+        }
         // Perform typechecking on all modules
         let mut queue = ResolveQueue::new();
         for module_idx in 0..self.modules.len() {
             let mut ctx = visitor::Ctx{
                 heap: &mut self.heap,
                 modules: &mut self.modules,
                 module_idx,
                 symbols: &mut self.symbol_table,
                 types: &mut self.type_table,
                 arch: &self.arch,
             };
             self.pass_typing.queue_module_definitions(&mut ctx, &mut queue);
         };
         while !queue.is_empty() {
-            let top = queue.pop().unwrap();
+            let top = queue.pop_front().unwrap();
             let mut ctx = visitor::Ctx{
                 heap: &mut self.heap,
                 modules: &mut self.modules,
                 module_idx: top.root_id.index as usize,
                 symbols: &mut self.symbol_table,
                 types: &mut self.type_table,
                 arch: &self.arch,
             };
             self.pass_typing.handle_module_definition(&mut ctx, &mut queue, top)?;
+        }
         // Rewrite nodes in tree, then prepare for execution of code
         for module_idx in 0..self.modules.len() {
             self.modules[module_idx].phase = ModuleCompilationPhase::Typed;
             let mut ctx = visitor::Ctx{
                 heap: &mut self.heap,
                 modules: &mut self.modules,
                 module_idx,
                 symbols: &mut self.symbol_table,
                 types: &mut self.type_table,
                 arch: &self.arch,
             };
             self.pass_rewriting.visit_module(&mut ctx)?;
             self.pass_stack_size.visit_module(&mut ctx)?;
+        }
         // Write out desired information
         if let Some(filename) = &self.write_ast_to {
             let mut writer = ASTWriter::new();
             let mut file = std::fs::File::create(std::path::Path::new(filename)).unwrap();
             writer.write_ast(&mut file, &self.heap);
+        }
         Ok(())
+    }
+}
 fn insert_builtin_type(type_table: &mut TypeTable, parts: Vec<ConcreteTypePart>, has_poly_var: bool, size: usize, alignment: usize) -> TypeId {
     const POLY_VARS: [PolymorphicVariable; 1] = [PolymorphicVariable{
         identifier: Identifier::new_empty(InputSpan::new()),
         is_in_use: false,
     }];
     let concrete_type = ConcreteType{ parts };
     let poly_var = if has_poly_var {
         POLY_VARS.as_slice()
     } else {
         &[]
     };
     return type_table.add_builtin_data_type(concrete_type, poly_var, size, alignment);
+}
 // Note: args and return type need to be a function because we need to know the function ID.
 fn insert_builtin_function<T: Fn(ProcedureDefinitionId) -> (Vec<(&'static str, ParserType)>, ParserType)> (
     p: &mut Parser, func_name: &str, polymorphic: &[&str], arg_and_return_fn: T
 ) {
     // Insert into AST (to get an ID), also prepare the polymorphic variables
     // we need later for the type table
     let mut ast_poly_vars = Vec::with_capacity(polymorphic.len());
     let mut type_poly_vars = Vec::with_capacity(polymorphic.len());
     for poly_var in polymorphic {
         let identifier = Identifier{ span: InputSpan::new(), value: p.string_pool.intern(poly_var.as_bytes()) } ;
         ast_poly_vars.push(identifier.clone());
         type_poly_vars.push(PolymorphicVariable{ identifier, is_in_use: false });
+    }
     let func_ident_ref = p.string_pool.intern(func_name.as_bytes());
     let procedure_id = p.heap.alloc_procedure_definition(|this| ProcedureDefinition {
         this,
         defined_in: RootId::new_invalid(),
         builtin: true,
         kind: ProcedureKind::Function,
         span: InputSpan::new(),
         identifier: Identifier{ span: InputSpan::new(), value: func_ident_ref.clone() },
         poly_vars: ast_poly_vars,
         return_type: None,
         parameters: Vec::new(),
         scope: ScopeId::new_invalid(),
         body: BlockStatementId::new_invalid(),
         monomorphs: Vec::new(),
     });
     // Modify AST with more information about the procedure
     let (arguments, return_type) = arg_and_return_fn(procedure_id);
     let mut parameters = Vec::with_capacity(arguments.len());
     for (arg_name, arg_type) in arguments {
         let identifier = Identifier{ span: InputSpan::new(), value: p.string_pool.intern(arg_name.as_bytes()) };
         let param_id = p.heap.alloc_variable(|this| Variable{
             this,
             kind: VariableKind::Parameter,
             parser_type: arg_type.clone(),
             identifier,
             relative_pos_in_parent: 0,
             unique_id_in_scope: 0
         });
         parameters.push(param_id);
+    }
     let func = &mut p.heap[procedure_id];
     func.parameters = parameters;
     func.return_type = Some(return_type);
     // Insert into symbol table
     p.symbol_table.insert_symbol(SymbolScope::Global, Symbol{
         name: func_ident_ref,
         variant: SymbolVariant::Definition(SymbolDefinition{
             defined_in_module: RootId::new_invalid(),
             defined_in_scope: SymbolScope::Global,
             definition_span: InputSpan::new(),
             identifier_span: InputSpan::new(),
             imported_at: None,
             class: DefinitionClass::Function,
             definition_id: procedure_id.upcast(),
         })
     }).unwrap();
     // Insert into type table
     let mut concrete_type = ConcreteType::default();
     concrete_type.parts.push(ConcreteTypePart::Function(procedure_id, type_poly_vars.len() as u32));
     for _ in 0..type_poly_vars.len() {
         concrete_type.parts.push(ConcreteTypePart::Void); // doesn't matter (I hope...)
+    }
     p.type_table.add_builtin_procedure_type(concrete_type, &type_poly_vars);
     // let mut concrete_type = ConcreteType::default();
     // concrete_type.parts.push(ConcreteTypePart::Function(procedure_id, type_poly_vars.len() as u32));
     //
     // for _ in 0..type_poly_vars.len() {
     //     concrete_type.parts.push(ConcreteTypePart::Void); // doesn't matter (I hope...)
     // }
     // p.type_table.add_builtin_procedure_type(concrete_type, &type_poly_vars);
+}
@@ \ No newline at end of file @@

src/protocol/parser/pass_typing.rs

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Show inline comments

 /// pass_typing
 ///
 /// Performs type inference and type checking. Type inference is implemented by
 /// applying constraints on (sub)trees of types. During this process the
 /// resolver takes the `ParserType` structs (the representation of the types
 /// written by the programmer), converts them to `InferenceType` structs (the
 /// temporary data structure used during type inference) and attempts to arrive
 /// at `ConcreteType` structs (the representation of a fully checked and
 /// validated type).
 ///
 /// The resolver will visit every statement and expression relevant to the
 /// procedure and insert and determine its initial type based on context (e.g. a
 /// return statement's expression must match the function's return type, an
 /// if statement's test expression must evaluate to a boolean). When all are
 /// visited we attempt to make progress in evaluating the types. Whenever a type
 /// is progressed we queue the related expressions for further type progression.
 /// Once no more expressions are in the queue the algorithm is finished. At this
 /// point either all types are inferred (or can be trivially implicitly
 /// determined), or we have incomplete types. In the latter case we return an
 /// error.
 ///
 /// TODO: Needs a thorough rewrite:
 ///  0. polymorph_progress is intentionally broken at the moment. Make it work
 ///     again and use a normal VecSomething.
 ///  1. The foundation for doing all of the work with predetermined indices
 ///     instead of with HashMaps is there, but it is not really used because of
 ///     time constraints. When time is available, rewrite the system such that
 ///     AST IDs are not needed, and only indices into arrays are used.
 ///  2. Remove the `msg` type?
 ///  3. Disallow certain types in certain operations (e.g. `Void`).
 macro_rules! debug_log_enabled {
     () => { false };
+}
 macro_rules! debug_log {
     ($format:literal) => {
         enabled_debug_print!(false, "types", $format);
     };
     ($format:literal, $($args:expr),*) => {
         enabled_debug_print!(false, "types", $format, $($args),*);
     };
+}
 use std::collections::VecDeque;
 use crate::collections::{ScopedBuffer, ScopedSection, DequeSet};
 use crate::protocol::ast::*;
 use crate::protocol::input_source::ParseError;
 use crate::protocol::parser::ModuleCompilationPhase;
 use crate::protocol::parser::type_table::*;
 use crate::protocol::parser::token_parsing::*;
 use super::visitor::{
     BUFFER_INIT_CAP_LARGE,
     BUFFER_INIT_CAP_SMALL,
     Ctx,
 };
 // -----------------------------------------------------------------------------
 // Inference type
 // -----------------------------------------------------------------------------
 const VOID_TEMPLATE: [InferenceTypePart; 1] = [ InferenceTypePart::Void ];
 const MESSAGE_TEMPLATE: [InferenceTypePart; 2] = [ InferenceTypePart::Message, InferenceTypePart::UInt8 ];
 const BOOL_TEMPLATE: [InferenceTypePart; 1] = [ InferenceTypePart::Bool ];
 const CHARACTER_TEMPLATE: [InferenceTypePart; 1] = [ InferenceTypePart::Character ];
 const STRING_TEMPLATE: [InferenceTypePart; 2] = [ InferenceTypePart::String, InferenceTypePart::Character ];
 const NUMBERLIKE_TEMPLATE: [InferenceTypePart; 1] = [ InferenceTypePart::NumberLike ];
 const INTEGERLIKE_TEMPLATE: [InferenceTypePart; 1] = [ InferenceTypePart::IntegerLike ];
 const ARRAY_TEMPLATE: [InferenceTypePart; 2] = [ InferenceTypePart::Array, InferenceTypePart::Unknown ];
 const SLICE_TEMPLATE: [InferenceTypePart; 2] = [ InferenceTypePart::Slice, InferenceTypePart::Unknown ];
 const ARRAYLIKE_TEMPLATE: [InferenceTypePart; 2] = [ InferenceTypePart::ArrayLike, InferenceTypePart::Unknown ];
 /// TODO: @performance Turn into PartialOrd+Ord to simplify checks
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub(crate) enum InferenceTypePart {
     // When we infer types of AST elements that support polymorphic arguments,
     // then we might have the case that multiple embedded types depend on the
     // polymorphic type (e.g. func bla(T a, T[] b) -> T[][]). If we can infer
     // the type in one place (e.g. argument a), then we may propagate this
     // information to other types (e.g. argument b and the return type). For
     // this reason we place markers in the `InferenceType` instances such that
     // we know which part of the type was originally a polymorphic argument.
     Marker(u32),
     // Completely unknown type, needs to be inferred
     Unknown,
     // Partially known type, may be inferred to to be the appropriate related
     // type.
     // IndexLike,      // index into array/slice
     NumberLike,     // any kind of integer/float
     IntegerLike,    // any kind of integer
     ArrayLike,      // array or slice. Note that this must have a subtype
     PortLike,       // input or output port
     // Special types that cannot be instantiated by the user
     Void, // For builtin functions that do not return anything
     // Concrete types without subtypes
     Bool,
     UInt8,
     UInt16,
     UInt32,
     UInt64,
     SInt8,
     SInt16,
     SInt32,
     SInt64,
     Character,
     String,
     // One subtype
     Message,
     Array,
     Slice,
     Input,
     Output,
     // Tuple with any number of subtypes (for practical reasons 1 element is impossible)
     Tuple(u32),
     // A user-defined type with any number of subtypes
     Instance(DefinitionId, u32)
+}
 impl InferenceTypePart {
     fn is_marker(&self) -> bool {
         match self {
             InferenceTypePart::Marker(_) => true,
             _ => false,
+        }
+    }
     /// Checks if the type is concrete, markers are interpreted as concrete
     /// types.
     fn is_concrete(&self) -> bool {
         use InferenceTypePart as ITP;
         match self {
             ITP::Unknown | ITP::NumberLike |
             ITP::IntegerLike | ITP::ArrayLike | ITP::PortLike => false,
             _ => true
+        }
+    }
     fn is_concrete_number(&self) -> bool {
         use InferenceTypePart as ITP;
         match self {
             ITP::UInt8 | ITP::UInt16 | ITP::UInt32 | ITP::UInt64 |
             ITP::SInt8 | ITP::SInt16 | ITP::SInt32 | ITP::SInt64 => true,
             _ => false,
+        }
+    }
     fn is_concrete_integer(&self) -> bool {
         use InferenceTypePart as ITP;
         match self {
             ITP::UInt8 | ITP::UInt16 | ITP::UInt32 | ITP::UInt64 |
             ITP::SInt8 | ITP::SInt16 | ITP::SInt32 | ITP::SInt64 => true,
             _ => false,
+        }
+    }
     fn is_concrete_arraylike(&self) -> bool {
         use InferenceTypePart as ITP;
         match self {
             ITP::Array | ITP::Slice | ITP::String | ITP::Message => true,
             _ => false,
+        }
+    }
     fn is_concrete_port(&self) -> bool {
         use InferenceTypePart as ITP;
         match self {
             ITP::Input | ITP::Output => true,
             _ => false,
+        }
+    }
     /// Checks if a part is less specific than the argument. Only checks for
     /// single-part inference (i.e. not the replacement of an `Unknown` variant
     /// with the argument)
     fn may_be_inferred_from(&self, arg: &InferenceTypePart) -> bool {
         use InferenceTypePart as ITP;
         (*self == ITP::IntegerLike && arg.is_concrete_integer()) ||
         (*self == ITP::NumberLike && (arg.is_concrete_number() || *arg == ITP::IntegerLike)) ||
         (*self == ITP::ArrayLike && arg.is_concrete_arraylike()) ||
         (*self == ITP::PortLike && arg.is_concrete_port())
+    }
     /// Checks if a part is more specific
     /// Returns the change in "iteration depth" when traversing this particular
     /// part. The iteration depth is used to traverse the tree in a linear
     /// fashion. It is basically `number_of_subtypes - 1`
     fn depth_change(&self) -> i32 {
         use InferenceTypePart as ITP;
         match &self {
             ITP::Unknown | ITP::NumberLike | ITP::IntegerLike |
             ITP::Void | ITP::Bool |
             ITP::UInt8 | ITP::UInt16 | ITP::UInt32 | ITP::UInt64 |
             ITP::SInt8 | ITP::SInt16 | ITP::SInt32 | ITP::SInt64 |
             ITP::Character => {
                 -1
             },
             ITP::Marker(_) |
             ITP::ArrayLike | ITP::Message | ITP::Array | ITP::Slice |
             ITP::PortLike | ITP::Input | ITP::Output | ITP::String => {
                 // One subtype, so do not modify depth
             },
             ITP::Tuple(num) | ITP::Instance(_, num) => {
                 (*num as i32) - 1
+            }
+        }
+    }
+}
 #[derive(Debug, Clone)]
 struct InferenceType {
     has_marker: bool,
     is_done: bool,
     parts: Vec<InferenceTypePart>,
+}
 impl InferenceType {
     /// Generates a new InferenceType. The two boolean flags will be checked in
     /// debug mode.
     fn new(has_marker: bool, is_done: bool, parts: Vec<InferenceTypePart>) -> Self {
         dbg_code!({
             debug_assert!(!parts.is_empty());
             let parts_body_marker = parts.iter().any(|v| v.is_marker());
             debug_assert_eq!(has_marker, parts_body_marker);
             let parts_done = parts.iter().all(|v| v.is_concrete());
             debug_assert_eq!(is_done, parts_done, "{:?}", parts);
         });
         Self{ has_marker, is_done, parts }
+    }
     /// Replaces a type subtree with the provided subtree. The caller must make
     /// sure the the replacement is a well formed type subtree.
     fn replace_subtree(&mut self, start_idx: usize, with: &[InferenceTypePart]) {
         let end_idx = Self::find_subtree_end_idx(&self.parts, start_idx);
         debug_assert_eq!(with.len(), Self::find_subtree_end_idx(with, 0));
         self.parts.splice(start_idx..end_idx, with.iter().cloned());
         self.recompute_is_done();
+    }
     // TODO: @performance, might all be done inline in the type inference methods
     fn recompute_is_done(&mut self) {
         self.is_done = self.parts.iter().all(|v| v.is_concrete());
+    }
     /// Seeks a body marker starting at the specified position. If a marker is
     /// found then its value and the index of the type subtree that follows it
     /// is returned.
     fn find_marker(&self, mut start_idx: usize) -> Option<(u32, usize)> {
         while start_idx < self.parts.len() {
             if let InferenceTypePart::Marker(marker) = &self.parts[start_idx] {
                 return Some((*marker, start_idx + 1))
+            }
             start_idx += 1;
+        }
         None
+    }
     /// Returns an iterator over all body markers and the partial type tree that
     /// follows those markers. If it is a problem that `InferenceType` is
     /// borrowed by the iterator, then use `find_body_marker`.
     fn marker_iter(&self) -> InferenceTypeMarkerIter {
         InferenceTypeMarkerIter::new(&self.parts)
+    }
     /// Given that the `parts` are a depth-first serialized tree of types, this
     /// function finds the subtree anchored at a specific node. The returned
     /// index is exclusive.
     fn find_subtree_end_idx(parts: &[InferenceTypePart], start_idx: usize) -> usize {
         let mut depth = 1;
         let mut idx = start_idx;
         while idx < parts.len() {
             depth += parts[idx].depth_change();
             if depth == 0 {
                 return idx + 1;
+            }
             idx += 1;
+        }
         // If here, then the inference type is malformed
         unreachable!("Malformed type: {:?}", parts);
+    }
     /// Call that attempts to infer the part at `to_infer.parts[to_infer_idx]`
     /// using the subtree at `template.parts[template_idx]`. Will return
     /// `Some(depth_change_due_to_traversal)` if type inference has been
     /// applied. In this case the indices will also be modified to point to the
     /// next part in both templates. If type inference has not (or: could not)
     /// be applied then `None` will be returned. Note that this might mean that
     /// the types are incompatible.
     ///
     /// As this is a helper functions, some assumptions: the parts are not
     /// exactly equal, and neither of them contains a marker. Also: only the
     /// `to_infer` parts are checked for inference. It might be that this
     /// function returns `None`, but that that `template` is still compatible
     /// with `to_infer`, e.g. when `template` has an `Unknown` part.
     fn infer_part_for_single_type(
         to_infer: &mut InferenceType, to_infer_idx: &mut usize,
         template_parts: &[InferenceTypePart], template_idx: &mut usize,
     ) -> Option<i32> {
         use InferenceTypePart as ITP;
         let to_infer_part = &to_infer.parts[*to_infer_idx];
         let template_part = &template_parts[*template_idx];
         // Check for programmer mistakes
         debug_assert_ne!(to_infer_part, template_part);
         debug_assert!(!to_infer_part.is_marker(), "marker encountered in 'infer part'");
         debug_assert!(!template_part.is_marker(), "marker encountered in 'template part'");
         // Inference of a somewhat-specified type
         if to_infer_part.may_be_inferred_from(template_part) {
             let depth_change = to_infer_part.depth_change();
             debug_assert_eq!(depth_change, template_part.depth_change());
             to_infer.parts[*to_infer_idx] = template_part.clone();
             *to_infer_idx += 1;
             *template_idx += 1;
             return Some(depth_change);
+        }
         // Inference of a completely unknown type
         if *to_infer_part == ITP::Unknown {
             // template part is different, so cannot be unknown, hence copy the
             // entire subtree. Make sure not to copy markers.
             let template_end_idx = Self::find_subtree_end_idx(template_parts, *template_idx);
             to_infer.parts[*to_infer_idx] = template_parts[*template_idx].clone(); // first element
             *to_infer_idx += 1;
             for template_idx in *template_idx + 1..template_end_idx {
                 let template_part = &template_parts[template_idx];
                 if !template_part.is_marker() {
                     to_infer.parts.insert(*to_infer_idx, template_part.clone());
                     *to_infer_idx += 1;
+                }
+            }
             *template_idx = template_end_idx;
             // Note: by definition the LHS was Unknown and the RHS traversed a
             // full subtree.
             return Some(-1);
+        }
         None
+    }
     /// Call that checks if the `to_check` part is compatible with the `infer`
     /// part. This is essentially a copy of `infer_part_for_single_type`, but
     /// without actually copying the type parts.
     fn check_part_for_single_type(
         to_check_parts: &[InferenceTypePart], to_check_idx: &mut usize,
         template_parts: &[InferenceTypePart], template_idx: &mut usize
     ) -> Option<i32> {
         use InferenceTypePart as ITP;
         let to_check_part = &to_check_parts[*to_check_idx];
         let template_part = &template_parts[*template_idx];
         // Checking programmer errors
         debug_assert_ne!(to_check_part, template_part);
         debug_assert!(!to_check_part.is_marker(), "marker encountered in 'to_check part'");
         debug_assert!(!template_part.is_marker(), "marker encountered in 'template part'");
         if to_check_part.may_be_inferred_from(template_part) {
             let depth_change = to_check_part.depth_change();
             debug_assert_eq!(depth_change, template_part.depth_change());
             *to_check_idx += 1;
             *template_idx += 1;
             return Some(depth_change);
+        }
         if *to_check_part == ITP::Unknown {
             *to_check_idx += 1;
             *template_idx = Self::find_subtree_end_idx(template_parts, *template_idx);
             // By definition LHS and RHS had depth change of -1
             return Some(-1);
+        }
         None
+    }
     /// Attempts to infer types between two `InferenceType` instances. This
     /// function is unsafe as it accepts pointers to work around Rust's
     /// borrowing rules. The caller must ensure that the pointers are distinct.
     unsafe fn infer_subtrees_for_both_types(
         type_a: *mut InferenceType, start_idx_a: usize,
         type_b: *mut InferenceType, start_idx_b: usize
     ) -> DualInferenceResult {
         debug_assert!(!std::ptr::eq(type_a, type_b), "encountered pointers to the same inference type");
         let type_a = &mut *type_a;
         let type_b = &mut *type_b;
         let mut modified_a = false;
         let mut modified_b = false;
         let mut idx_a = start_idx_a;
         let mut idx_b = start_idx_b;
         let mut depth = 1;
         while depth > 0 {
             // Advance indices if we encounter markers or equal parts
             let part_a = &type_a.parts[idx_a];
             let part_b = &type_b.parts[idx_b];
             if part_a == part_b {
                 let depth_change = part_a.depth_change();
                 depth += depth_change;
                 debug_assert_eq!(depth_change, part_b.depth_change());
                 idx_a += 1;
                 idx_b += 1;
                 continue;
+            }
             if part_a.is_marker() { idx_a += 1; continue; }
             if part_b.is_marker() { idx_b += 1; continue; }
             // Types are not equal and are both not markers
             if let Some(depth_change) = Self::infer_part_for_single_type(type_a, &mut idx_a, &type_b.parts, &mut idx_b) {
                 depth += depth_change;
                 modified_a = true;
                 continue;
+            }
             if let Some(depth_change) = Self::infer_part_for_single_type(type_b, &mut idx_b, &type_a.parts, &mut idx_a) {
                 depth += depth_change;
                 modified_b = true;
                 continue;
+            }
             // Types can not be inferred in any way: types must be incompatible
             return DualInferenceResult::Incompatible;
+        }
         if modified_a { type_a.recompute_is_done(); }
         if modified_b { type_b.recompute_is_done(); }
         // If here then we completely inferred the subtrees.
         match (modified_a, modified_b) {
             (false, false) => DualInferenceResult::Neither,
             (false, true) => DualInferenceResult::Second,
             (true, false) => DualInferenceResult::First,
             (true, true) => DualInferenceResult::Both
+        }
+    }
     /// Attempts to infer the first subtree based on the template. Like
     /// `infer_subtrees_for_both_types`, but now only applying inference to
     /// `to_infer` based on the type information in `template`.
     ///
     /// The `forced_template` flag controls whether `to_infer` is considered
     /// valid if it is more specific then the template. When `forced_template`
     /// is false, then as long as the `to_infer` and `template` types are
     /// compatible the inference will succeed. If `forced_template` is true,
     /// then `to_infer` MUST be less specific than `template` (e.g.
     /// `IntegerLike` is less specific than `UInt32`)
     fn infer_subtree_for_single_type(
         to_infer: &mut InferenceType, mut to_infer_idx: usize,
         template: &[InferenceTypePart], mut template_idx: usize,
         forced_template: bool,
     ) -> SingleInferenceResult {
         let mut modified = false;
         let mut depth = 1;
         while depth > 0 {
             let to_infer_part = &to_infer.parts[to_infer_idx];
             let template_part = &template[template_idx];
             if to_infer_part == template_part {
                 let depth_change = to_infer_part.depth_change();
                 depth += depth_change;
                 debug_assert_eq!(depth_change, template_part.depth_change());
                 to_infer_idx += 1;
                 template_idx += 1;
                 continue;
+            }
             if to_infer_part.is_marker() { to_infer_idx += 1; continue; }
             if template_part.is_marker() { template_idx += 1; continue; }
             // Types are not equal and not markers. So check if we can infer
             // anything
             if let Some(depth_change) = Self::infer_part_for_single_type(
                 to_infer, &mut to_infer_idx, template, &mut template_idx
             ) {
                 depth += depth_change;
                 modified = true;
                 continue;
+            }
             if !forced_template {
                 // We cannot infer anything, but the template may still be
                 // compatible with the type we're inferring
                 if let Some(depth_change) = Self::check_part_for_single_type(
                     template, &mut template_idx, &to_infer.parts, &mut to_infer_idx
                 ) {
                     depth += depth_change;
                     continue;
+                }
+            }
             return SingleInferenceResult::Incompatible
+        }
         if modified {
             to_infer.recompute_is_done();
             return SingleInferenceResult::Modified;
         } else {
             return SingleInferenceResult::Unmodified;
+        }
+    }
     /// Checks if both types are compatible, doesn't perform any inference
     fn check_subtrees(
         type_parts_a: &[InferenceTypePart], start_idx_a: usize,
         type_parts_b: &[InferenceTypePart], start_idx_b: usize
     ) -> bool {
         let mut depth = 1;
         let mut idx_a = start_idx_a;
         let mut idx_b = start_idx_b;
         while depth > 0 {
             let part_a = &type_parts_a[idx_a];
             let part_b = &type_parts_b[idx_b];
             if part_a == part_b {
                 let depth_change = part_a.depth_change();
                 depth += depth_change;
                 debug_assert_eq!(depth_change, part_b.depth_change());
                 idx_a += 1;
                 idx_b += 1;
                 continue;
+            }
             if part_a.is_marker() { idx_a += 1; continue; }
             if part_b.is_marker() { idx_b += 1; continue; }
             if let Some(depth_change) = Self::check_part_for_single_type(
                 type_parts_a, &mut idx_a, type_parts_b, &mut idx_b
             ) {
                 depth += depth_change;
                 continue;
+            }
             if let Some(depth_change) = Self::check_part_for_single_type(
                 type_parts_b, &mut idx_b, type_parts_a, &mut idx_a
             ) {
                 depth += depth_change;
                 continue;
+            }
             return false;
+        }
         true
+    }
     /// Performs the conversion of the inference type into a concrete type.
     /// By calling this function you must make sure that no unspecified types
     /// (e.g. Unknown or IntegerLike) exist in the type. Will not clear or check
     /// if the supplied `ConcreteType` is empty, will simply append to the parts
     /// vector.
     fn write_concrete_type(&self, concrete_type: &mut ConcreteType) {
         use InferenceTypePart as ITP;
         use ConcreteTypePart as CTP;
         // Make sure inference type is specified but concrete type is not yet specified
         debug_assert!(!self.parts.is_empty());
         concrete_type.parts.reserve(self.parts.len());
         let mut idx = 0;
         while idx < self.parts.len() {
             let part = &self.parts[idx];
             let converted_part = match part {
                 ITP::Marker(_) => {
                     // Markers are removed when writing to the concrete type.
                     idx += 1;
                     continue;
                 },
                 ITP::Unknown | ITP::NumberLike |
                 ITP::IntegerLike | ITP::ArrayLike | ITP::PortLike => {
                     // Should not happen if type inferencing works correctly: we
                     // should have returned a programmer-readable error or have
                     // inferred all types.
                     unreachable!("attempted to convert inference type part {:?} into concrete type", part);
                 },
                 ITP::Void => CTP::Void,
                 ITP::Message => CTP::Message,
                 ITP::Bool => CTP::Bool,
                 ITP::UInt8 => CTP::UInt8,
                 ITP::UInt16 => CTP::UInt16,
                 ITP::UInt32 => CTP::UInt32,
                 ITP::UInt64 => CTP::UInt64,
                 ITP::SInt8 => CTP::SInt8,
                 ITP::SInt16 => CTP::SInt16,
                 ITP::SInt32 => CTP::SInt32,
                 ITP::SInt64 => CTP::SInt64,
                 ITP::Character => CTP::Character,
                 ITP::String => {
                     // Inferred type has a 'char' subtype to simplify array
                     // checking, we remove it here.
                     debug_assert_eq!(self.parts[idx + 1], InferenceTypePart::Character);
                     idx += 1;
                     CTP::String
                 },
                 ITP::Array => CTP::Array,
                 ITP::Slice => CTP::Slice,
                 ITP::Input => CTP::Input,
                 ITP::Output => CTP::Output,
                 ITP::Tuple(num) => CTP::Tuple(*num),
                 ITP::Instance(id, num) => CTP::Instance(*id, *num),
             };
             concrete_type.parts.push(converted_part);
             idx += 1;
+        }
+    }
     /// Writes a human-readable version of the type to a string. This is used
     /// to display error messages
     fn write_display_name(
         buffer: &mut String, heap: &Heap, parts: &[InferenceTypePart], mut idx: usize
     ) -> usize {
         use InferenceTypePart as ITP;
         match &parts[idx] {
             ITP::Marker(_marker_idx) => {
                 if debug_log_enabled!() {
                     buffer.push_str(&format!("{{Marker:{}}}", *_marker_idx));
+                }
                 idx = Self::write_display_name(buffer, heap, parts, idx + 1);
             },
             ITP::Unknown => buffer.push_str("?"),
             ITP::NumberLike => buffer.push_str("numberlike"),
             ITP::IntegerLike => buffer.push_str("integerlike"),
             ITP::ArrayLike => {
                 idx = Self::write_display_name(buffer, heap, parts, idx + 1);
                 buffer.push_str("[?]");
             },
             ITP::PortLike => {
                 buffer.push_str("portlike<");
                 idx = Self::write_display_name(buffer, heap, parts, idx + 1);
                 buffer.push('>');
+            }
             ITP::Void => buffer.push_str("void"),
             ITP::Bool => buffer.push_str(KW_TYPE_BOOL_STR),
             ITP::UInt8 => buffer.push_str(KW_TYPE_UINT8_STR),
             ITP::UInt16 => buffer.push_str(KW_TYPE_UINT16_STR),
             ITP::UInt32 => buffer.push_str(KW_TYPE_UINT32_STR),
             ITP::UInt64 => buffer.push_str(KW_TYPE_UINT64_STR),
             ITP::SInt8 => buffer.push_str(KW_TYPE_SINT8_STR),
             ITP::SInt16 => buffer.push_str(KW_TYPE_SINT16_STR),
             ITP::SInt32 => buffer.push_str(KW_TYPE_SINT32_STR),
             ITP::SInt64 => buffer.push_str(KW_TYPE_SINT64_STR),
             ITP::Character => buffer.push_str(KW_TYPE_CHAR_STR),
             ITP::String => {
                 buffer.push_str(KW_TYPE_STRING_STR);
                 idx += 1; // skip the 'char' subtype
             },
             ITP::Message => {
                 buffer.push_str(KW_TYPE_MESSAGE_STR);
                 buffer.push('<');
                 idx = Self::write_display_name(buffer, heap, parts, idx + 1);
                 buffer.push('>');
             },
             ITP::Array => {
                 idx = Self::write_display_name(buffer, heap, parts, idx + 1);
                 buffer.push_str("[]");
             },
             ITP::Slice => {
                 idx = Self::write_display_name(buffer, heap, parts, idx + 1);
                 buffer.push_str("[..]");
             },
             ITP::Input => {
                 buffer.push_str(KW_TYPE_IN_PORT_STR);
                 buffer.push('<');
                 idx = Self::write_display_name(buffer, heap, parts, idx + 1);
                 buffer.push('>');
             },
             ITP::Output => {
                 buffer.push_str(KW_TYPE_OUT_PORT_STR);
                 buffer.push('<');
                 idx = Self::write_display_name(buffer, heap, parts, idx + 1);
                 buffer.push('>');
             },
             ITP::Tuple(num_sub) => {
                 buffer.push('(');
                 if *num_sub > 0 {
                     idx = Self::write_display_name(buffer, heap, parts, idx + 1);
                     for _sub_idx in 1..*num_sub {
                         buffer.push_str(", ");
                         idx = Self::write_display_name(buffer, heap, parts, idx + 1);
+                    }
+                }
                 buffer.push(')');
+            }
             ITP::Instance(definition_id, num_sub) => {
                 let definition = &heap[*definition_id];
                 buffer.push_str(definition.identifier().value.as_str());
                 if *num_sub > 0 {
                     buffer.push('<');
                     idx = Self::write_display_name(buffer, heap, parts, idx + 1);
                     for _sub_idx in 1..*num_sub {
                         buffer.push_str(", ");
                         idx = Self::write_display_name(buffer, heap, parts, idx + 1);
+                    }
                     buffer.push('>');
+                }
             },
+        }
         idx
+    }
     /// Returns the display name of a (part of) the type tree. Will allocate a
     /// string.
     fn partial_display_name(heap: &Heap, parts: &[InferenceTypePart]) -> String {
         let mut buffer = String::with_capacity(parts.len() * 6);
         Self::write_display_name(&mut buffer, heap, parts, 0);
         buffer
+    }
     /// Returns the display name of the full type tree. Will allocate a string.
     fn display_name(&self, heap: &Heap) -> String {
         Self::partial_display_name(heap, &self.parts)
+    }
+}
 impl Default for InferenceType {
     fn default() -> Self {
         Self{
             has_marker: false,
             is_done: false,
             parts: Vec::new(),
+        }
+    }
+}
 /// Iterator over the subtrees that follow a marker in an `InferenceType`
 /// instance. Returns immutable slices over the internal parts
 struct InferenceTypeMarkerIter<'a> {
     parts: &'a [InferenceTypePart],
     idx: usize,
+}
 impl<'a> InferenceTypeMarkerIter<'a> {
     fn new(parts: &'a [InferenceTypePart]) -> Self {
         Self{ parts, idx: 0 }
+    }
+}
 impl<'a> Iterator for InferenceTypeMarkerIter<'a> {
     type Item = (u32, &'a [InferenceTypePart]);
     fn next(&mut self) -> Option<Self::Item> {
         // Iterate until we find a marker
         while self.idx < self.parts.len() {
             if let InferenceTypePart::Marker(marker) = self.parts[self.idx] {
                 // Found a marker, find the subtree end
                 let start_idx = self.idx + 1;
                 let end_idx = InferenceType::find_subtree_end_idx(self.parts, start_idx);
                 // Modify internal index, then return items
                 self.idx = end_idx;
                 return Some((marker, &self.parts[start_idx..end_idx]));
+            }
             self.idx += 1;
+        }
         None
+    }
+}
 #[derive(Debug, PartialEq, Eq)]
 enum DualInferenceResult {
     Neither,        // neither argument is clarified
     First,          // first argument is clarified using the second one
     Second,         // second argument is clarified using the first one
     Both,           // both arguments are clarified
     Incompatible,   // types are incompatible: programmer error
+}
 impl DualInferenceResult {
     fn modified_lhs(&self) -> bool {
         match self {
             DualInferenceResult::First | DualInferenceResult::Both => true,
             _ => false
+        }
+    }
     fn modified_rhs(&self) -> bool {
         match self {
             DualInferenceResult::Second | DualInferenceResult::Both => true,
             _ => false
+        }
+    }
+}
 #[derive(Debug, PartialEq, Eq)]
 enum SingleInferenceResult {
     Unmodified,
     Modified,
     Incompatible
+}
 // -----------------------------------------------------------------------------
 // PassTyping - Public Interface
 // -----------------------------------------------------------------------------
 type InferNodeIndex = usize;
 type PolyDataIndex = isize;
 type VarDataIndex = usize;
 pub(crate) struct ResolveQueueElement {
     // Note that using the `definition_id` and the `monomorph_idx` one may
     // query the type table for the full procedure type, thereby retrieving
     // the polymorphic arguments to the procedure.
     pub(crate) root_id: RootId,
     pub(crate) definition_id: DefinitionId,
     pub(crate) reserved_type_id: TypeId,
     pub(crate) reserved_monomorph_index: u32,
+}
-pub(crate) type ResolveQueue = Vec<ResolveQueueElement>;
+pub(crate) type ResolveQueue = VecDeque<ResolveQueueElement>;
 struct InferenceNode {
     // filled in during type inference
     expr_type: InferenceType,               // result type from expression
     expr_id: ExpressionId,                  // expression that is evaluated
     inference_rule: InferenceRule,          // rule used to infer node type
     parent_index: Option<InferNodeIndex>,   // parent of inference node
     field_index: i32,                       // index of struct field or tuple member
     poly_data_index: PolyDataIndex,         // index to inference data for polymorphic types
     // filled in once type inference is done
     info_type_id: TypeId,
     info_variant: ExpressionInfoVariant,
+}
 impl InferenceNode {
     #[inline]
     fn as_expression_info(&self) -> ExpressionInfo {
         return ExpressionInfo {
             type_id: self.info_type_id,
             variant: self.info_variant
+        }
+    }
+}
 /// Inferencing rule to apply. Some of these are reasonably generic. Other ones
 /// require so much custom logic that we'll not try to come up with an
 /// abstraction.
 enum InferenceRule {
     Noop,
     MonoTemplate(InferenceRuleTemplate),
     BiEqual(InferenceRuleBiEqual),
     TriEqualArgs(InferenceRuleTriEqualArgs),
     TriEqualAll(InferenceRuleTriEqualAll),
     Concatenate(InferenceRuleTwoArgs),
     IndexingExpr(InferenceRuleIndexingExpr),
     SlicingExpr(InferenceRuleSlicingExpr),
     SelectStructField(InferenceRuleSelectStructField),
     SelectTupleMember(InferenceRuleSelectTupleMember),
     LiteralStruct(InferenceRuleLiteralStruct),
     LiteralEnum,
     LiteralUnion(InferenceRuleLiteralUnion),
     LiteralArray(InferenceRuleLiteralArray),
     LiteralTuple(InferenceRuleLiteralTuple),
     CastExpr(InferenceRuleCastExpr),
     CallExpr(InferenceRuleCallExpr),
     VariableExpr(InferenceRuleVariableExpr),
+}
 impl InferenceRule {
     union_cast_method_impl!(as_mono_template, InferenceRuleTemplate, InferenceRule::MonoTemplate);
     union_cast_method_impl!(as_bi_equal, InferenceRuleBiEqual, InferenceRule::BiEqual);
     union_cast_method_impl!(as_tri_equal_args, InferenceRuleTriEqualArgs, InferenceRule::TriEqualArgs);
     union_cast_method_impl!(as_tri_equal_all, InferenceRuleTriEqualAll, InferenceRule::TriEqualAll);
     union_cast_method_impl!(as_concatenate, InferenceRuleTwoArgs, InferenceRule::Concatenate);
     union_cast_method_impl!(as_indexing_expr, InferenceRuleIndexingExpr, InferenceRule::IndexingExpr);
     union_cast_method_impl!(as_slicing_expr, InferenceRuleSlicingExpr, InferenceRule::SlicingExpr);
     union_cast_method_impl!(as_select_struct_field, InferenceRuleSelectStructField, InferenceRule::SelectStructField);
     union_cast_method_impl!(as_select_tuple_member, InferenceRuleSelectTupleMember, InferenceRule::SelectTupleMember);
     union_cast_method_impl!(as_literal_struct, InferenceRuleLiteralStruct, InferenceRule::LiteralStruct);
     union_cast_method_impl!(as_literal_union, InferenceRuleLiteralUnion, InferenceRule::LiteralUnion);
     union_cast_method_impl!(as_literal_array, InferenceRuleLiteralArray, InferenceRule::LiteralArray);
     union_cast_method_impl!(as_literal_tuple, InferenceRuleLiteralTuple, InferenceRule::LiteralTuple);
     union_cast_method_impl!(as_cast_expr, InferenceRuleCastExpr, InferenceRule::CastExpr);
     union_cast_method_impl!(as_call_expr, InferenceRuleCallExpr, InferenceRule::CallExpr);
     union_cast_method_impl!(as_variable_expr, InferenceRuleVariableExpr, InferenceRule::VariableExpr);
+}
 // Note: InferenceRuleTemplate is `Copy`, so don't add dynamically allocated
 // members in the future (or review places where this struct is copied)
 #[derive(Clone, Copy)]
 struct InferenceRuleTemplate {
     template: &'static [InferenceTypePart],
     application: InferenceRuleTemplateApplication,
+}
 impl InferenceRuleTemplate {
     fn new_none() -> Self {
         return Self{
             template: &[],
             application: InferenceRuleTemplateApplication::None,
         };
+    }
     fn new_forced(template: &'static [InferenceTypePart]) -> Self {
         return Self{
             template,
             application: InferenceRuleTemplateApplication::Forced,
         };
+    }
     fn new_template(template: &'static [InferenceTypePart]) -> Self {
         return Self{
             template,
             application: InferenceRuleTemplateApplication::Template,
+        }
+    }
+}
 #[derive(Clone, Copy)]
 enum InferenceRuleTemplateApplication {
     None, // do not apply template, silly, but saves some bytes
     Forced,
     Template,
+}
 /// Type equality applied to 'self' and the argument. An optional template will
 /// be applied to 'self' first. Example: "bitwise not"
 struct InferenceRuleBiEqual {
     template: InferenceRuleTemplate,
     argument_index: InferNodeIndex,
+}
 /// Type equality applied to two arguments. Template can be applied to 'self'
 /// (generally forced, since this rule does not apply a type equality constraint
 /// to 'self') and the two arguments. Example: "equality operator"
 struct InferenceRuleTriEqualArgs {
     argument_template: InferenceRuleTemplate,
     result_template: InferenceRuleTemplate,
     argument1_index: InferNodeIndex,
     argument2_index: InferNodeIndex,
+}
 /// Type equality applied to 'self' and two arguments. Template may be
 /// optionally applied to 'self'. Example: "addition operator"
 struct InferenceRuleTriEqualAll {
     template: InferenceRuleTemplate,
     argument1_index: InferNodeIndex,
     argument2_index: InferNodeIndex,
+}
 /// Information for an inference rule that is applied to 'self' and two
 /// arguments, see `InferenceRule` for its meaning.
 struct InferenceRuleTwoArgs {
     argument1_index: InferNodeIndex,
     argument2_index: InferNodeIndex,
+}
 struct InferenceRuleIndexingExpr {
     subject_index: InferNodeIndex,
     index_index: InferNodeIndex,
+}
 struct InferenceRuleSlicingExpr {
     subject_index: InferNodeIndex,
     from_index: InferNodeIndex,
     to_index: InferNodeIndex,
+}
 struct InferenceRuleSelectStructField {
     subject_index: InferNodeIndex,
     selected_field: Identifier,
+}
 struct InferenceRuleSelectTupleMember {
     subject_index: InferNodeIndex,
     selected_index: u64,
+}
 struct InferenceRuleLiteralStruct {
     element_indices: Vec<InferNodeIndex>,
+}
 struct InferenceRuleLiteralUnion {
     element_indices: Vec<InferNodeIndex>
+}
 struct InferenceRuleLiteralArray {
     element_indices: Vec<InferNodeIndex>
+}
 struct InferenceRuleLiteralTuple {
     element_indices: Vec<InferNodeIndex>
+}
 struct InferenceRuleCastExpr {
     subject_index: InferNodeIndex,
+}
 struct InferenceRuleCallExpr {
     argument_indices: Vec<InferNodeIndex>
+}
 /// Data associated with a variable expression: an expression that reads the
 /// value from a variable.
 struct InferenceRuleVariableExpr {
     var_data_index: VarDataIndex, // shared variable information
+}
 /// This particular visitor will recurse depth-first into the AST and ensures
 /// that all expressions have the appropriate types.
 pub(crate) struct PassTyping {
     // Current definition we're typechecking.
     reserved_type_id: TypeId,
     reserved_monomorph_index: u32,
     procedure_id: ProcedureDefinitionId,
     procedure_kind: ProcedureKind,
     poly_vars: Vec<ConcreteType>,
     // Temporary variables during construction of inference rulesr
     parent_index: Option<InferNodeIndex>,
     // Buffers for iteration over various types
     var_buffer: ScopedBuffer<VariableId>,
     expr_buffer: ScopedBuffer<ExpressionId>,
     stmt_buffer: ScopedBuffer<StatementId>,
     bool_buffer: ScopedBuffer<bool>,
     index_buffer: ScopedBuffer<usize>,
     definition_buffer: ScopedBuffer<DefinitionId>,
     poly_progress_buffer: ScopedBuffer<u32>,
     // Mapping from parser type to inferred type. We attempt to continue to
     // specify these types until we're stuck or we've fully determined the type.
     infer_nodes: Vec<InferenceNode>,                     // will be transferred to type table at end
     poly_data: Vec<PolyData>,       // data for polymorph inference
     var_data: Vec<VarData>,
     // Keeping track of which expressions need to be reinferred because the
     // expressions they're linked to made progression on an associated type
     node_queued: DequeSet<InferNodeIndex>,
+}
 /// Generic struct that is used to store inferred types associated with
 /// polymorphic types.
 struct PolyData {
     first_rule_application: bool,
     definition_id: DefinitionId, // the definition, only used for user feedback
     /// Inferred types of the polymorphic variables as they are written down
     /// at the type's definition.
     poly_vars: Vec<InferenceType>,
     expr_types: PolyDataTypes,
+}
 // silly structure, just so we can use `PolyDataTypeIndex` ergonomically while
 // making sure we're still capable of borrowing from `poly_vars`.
 struct PolyDataTypes {
     /// Inferred types of associated types (e.g. struct fields, tuple members,
     /// function arguments). These types may depend on the polymorphic variables
     /// defined above.
     associated: Vec<InferenceType>,
     /// Inferred "returned" type (e.g. if a struct field is selected, then this
     /// contains the type of the selected field, for a function call it contains
     /// the return type). May depend on the polymorphic variables defined above.
     returned: InferenceType,
+}
 #[derive(Clone, Copy)]
 enum PolyDataTypeIndex {
     Associated(usize), // indexes into `PolyData.associated`
     Returned,
+}
 impl PolyDataTypes {
     fn get_type(&self, index: PolyDataTypeIndex) -> &InferenceType {
         match index {
             PolyDataTypeIndex::Associated(index) => return &self.associated[index],
             PolyDataTypeIndex::Returned => return &self.returned,
+        }
+    }
     fn get_type_mut(&mut self, index: PolyDataTypeIndex) -> &mut InferenceType {
         match index {
             PolyDataTypeIndex::Associated(index) => return &mut self.associated[index],
             PolyDataTypeIndex::Returned => return &mut self.returned,
+        }
+    }
+}
 struct VarData {
     var_id: VariableId,
     var_type: InferenceType,
     used_at: Vec<InferNodeIndex>, // of variable expressions
     linked_var: Option<VarDataIndex>,
+}
 impl PassTyping {
     pub(crate) fn new() -> Self {
         PassTyping {
             reserved_type_id: TypeId::new_invalid(),
             reserved_monomorph_index: u32::MAX,
             procedure_id: ProcedureDefinitionId::new_invalid(),
             procedure_kind: ProcedureKind::Function,
             poly_vars: Vec::new(),
             parent_index: None,
             var_buffer: ScopedBuffer::with_capacity(BUFFER_INIT_CAP_LARGE),
             expr_buffer: ScopedBuffer::with_capacity(BUFFER_INIT_CAP_LARGE),
             stmt_buffer: ScopedBuffer::with_capacity(BUFFER_INIT_CAP_LARGE),
             bool_buffer: ScopedBuffer::with_capacity(BUFFER_INIT_CAP_SMALL),
             index_buffer: ScopedBuffer::with_capacity(BUFFER_INIT_CAP_SMALL),
             definition_buffer: ScopedBuffer::with_capacity(BUFFER_INIT_CAP_LARGE),
             poly_progress_buffer: ScopedBuffer::with_capacity(BUFFER_INIT_CAP_SMALL),
             infer_nodes: Vec::with_capacity(BUFFER_INIT_CAP_LARGE),
             poly_data: Vec::with_capacity(BUFFER_INIT_CAP_SMALL),
             var_data: Vec::with_capacity(BUFFER_INIT_CAP_SMALL),
             node_queued: DequeSet::new(),
+        }
+    }
     pub(crate) fn queue_module_definitions(&mut self, ctx: &mut Ctx, queue: &mut ResolveQueue) {
         debug_assert_eq!(ctx.module().phase, ModuleCompilationPhase::ValidatedAndLinked);
         let root_id = ctx.module().root_id;
         let root = &ctx.heap.protocol_descriptions[root_id];
         let definitions_section = self.definition_buffer.start_section_initialized(&root.definitions);
         for definition_id in definitions_section.iter_copied() {
             let definition = &ctx.heap[definition_id];
             let first_concrete_part_and_procedure_id = match definition {
                 Definition::Procedure(definition) => {
                     if definition.poly_vars.is_empty() {
                         if definition.kind == ProcedureKind::Function {
                             Some((ConcreteTypePart::Function(definition.this, 0), definition.this))
                         } else {
                             Some((ConcreteTypePart::Component(definition.this, 0), definition.this))
+                        }
                     } else {
                         None
+                    }
+                }
                 Definition::Enum(_) | Definition::Struct(_) | Definition::Union(_) => None,
             };
             if let Some((first_concrete_part, procedure_id)) = first_concrete_part_and_procedure_id {
                 let procedure = &mut ctx.heap[procedure_id];
                 let monomorph_index = procedure.monomorphs.len() as u32;
                 procedure.monomorphs.push(ProcedureDefinitionMonomorph::new_invalid());
                 let concrete_type = ConcreteType{ parts: vec![first_concrete_part] };
                 let type_id = ctx.types.reserve_procedure_monomorph_type_id(&definition_id, concrete_type, monomorph_index);
-                queue.push(ResolveQueueElement{
+                queue.push_back(ResolveQueueElement{
                     root_id,
                     definition_id,
                     reserved_type_id: type_id,
                     reserved_monomorph_index: monomorph_index,
                 })
+            }
+        }
         definitions_section.forget();
+    }
     pub(crate) fn handle_module_definition(
         &mut self, ctx: &mut Ctx, queue: &mut ResolveQueue, element: ResolveQueueElement
     ) -> VisitorResult {
         self.reset();
         debug_assert_eq!(ctx.module().root_id, element.root_id);
         debug_assert!(self.poly_vars.is_empty());
         // Prepare for visiting the definition
         self.reserved_type_id = element.reserved_type_id;
         self.reserved_monomorph_index = element.reserved_monomorph_index;
         let proc_base = ctx.types.get_base_definition(&element.definition_id).unwrap();
         if proc_base.is_polymorph {
             let monomorph = ctx.types.get_monomorph(element.reserved_type_id);
             for poly_arg in monomorph.concrete_type.embedded_iter(0) {
                 self.poly_vars.push(ConcreteType{ parts: Vec::from(poly_arg) });
+            }
+        }
         // Visit the definition, setting up the type resolving process, then
         // (attempt to) resolve all types
         self.visit_definition(ctx, element.definition_id)?;
         self.resolve_types(ctx, queue)?;
         Ok(())
+    }
     fn reset(&mut self) {
         self.reserved_type_id = TypeId::new_invalid();
         self.procedure_id = ProcedureDefinitionId::new_invalid();
         self.procedure_kind = ProcedureKind::Function;
         self.poly_vars.clear();
         self.parent_index = None;
         self.infer_nodes.clear();
         self.poly_data.clear();
         self.var_data.clear();
         self.node_queued.clear();
+    }
+}
 // -----------------------------------------------------------------------------
 // PassTyping - Visitor-like implementation
 // -----------------------------------------------------------------------------
 type VisitorResult = Result<(), ParseError>;
 type VisitExprResult = Result<InferNodeIndex, ParseError>;
 impl PassTyping {
     // Definitions
     fn visit_definition(&mut self, ctx: &mut Ctx, id: DefinitionId) -> VisitorResult {
         return visitor_recursive_definition_impl!(self, &ctx.heap[id], ctx);
+    }
     fn visit_enum_definition(&mut self, _: &mut Ctx, _: EnumDefinitionId) -> VisitorResult { return Ok(()) }
     fn visit_struct_definition(&mut self, _: &mut Ctx, _: StructDefinitionId) -> VisitorResult { return Ok(()) }
     fn visit_union_definition(&mut self, _: &mut Ctx, _: UnionDefinitionId) -> VisitorResult { return Ok(()) }
     fn visit_procedure_definition(&mut self, ctx: &mut Ctx, id: ProcedureDefinitionId) -> VisitorResult {
         let procedure_def = &ctx.heap[id];
         self.procedure_id = id;
         self.procedure_kind = procedure_def.kind;
         let body_id = procedure_def.body;
         debug_log!("{}", "-".repeat(50));
         debug_log!("Visiting procedure: '{}' (id: {}, kind: {:?})", procedure_def.identifier.value.as_str(), id.0.index, procedure_def.kind);
         debug_log!("{}", "-".repeat(50));
         // Visit parameters
         let section = self.var_buffer.start_section_initialized(procedure_def.parameters.as_slice());
         for param_id in section.iter_copied() {
             let param = &ctx.heap[param_id];
             let var_type = self.determine_inference_type_from_parser_type_elements(&param.parser_type.elements, true);
             debug_assert!(var_type.is_done, "expected function arguments to be concrete types");
             self.var_data.push(VarData{
                 var_id: param_id,
                 var_type,
                 used_at: Vec::new(),
                 linked_var: None
             })
+        }
         section.forget();
         // Visit all of the expressions within the body
         self.parent_index = None;
         return self.visit_block_stmt(ctx, body_id);
+    }
     // Statements
     fn visit_stmt(&mut self, ctx: &mut Ctx, id: StatementId) -> VisitorResult {
         return visitor_recursive_statement_impl!(self, &ctx.heap[id], ctx, Ok(()));
+    }
     fn visit_block_stmt(&mut self, ctx: &mut Ctx, id: BlockStatementId) -> VisitorResult {
         // Transfer statements for traversal
         let block = &ctx.heap[id];
         let section = self.stmt_buffer.start_section_initialized(block.statements.as_slice());
         for stmt_id in section.iter_copied() {
             self.visit_stmt(ctx, stmt_id)?;
+        }
         section.forget();
         Ok(())
+    }
     fn visit_local_stmt(&mut self, ctx: &mut Ctx, id: LocalStatementId) -> VisitorResult {
         return visitor_recursive_local_impl!(self, &ctx.heap[id], ctx);
+    }
     fn visit_local_memory_stmt(&mut self, ctx: &mut Ctx, id: MemoryStatementId) -> VisitorResult {
         let memory_stmt = &ctx.heap[id];
         let initial_expr_id = memory_stmt.initial_expr;
         let local = &ctx.heap[memory_stmt.variable];
         let var_type = self.determine_inference_type_from_parser_type_elements(&local.parser_type.elements, true);
         self.var_data.push(VarData{
             var_id: memory_stmt.variable,
             var_type,
             used_at: Vec::new(),
             linked_var: None,
         });
         // Process the initial value
         self.visit_assignment_expr(ctx, initial_expr_id)?;
         Ok(())
+    }
     fn visit_local_channel_stmt(&mut self, ctx: &mut Ctx, id: ChannelStatementId) -> VisitorResult {
         let channel_stmt = &ctx.heap[id];
         let from_var_index = self.var_data.len() as VarDataIndex;
         let to_var_index = from_var_index + 1;
         let from_local = &ctx.heap[channel_stmt.from];
         let from_var_type = self.determine_inference_type_from_parser_type_elements(&from_local.parser_type.elements, true);
         self.var_data.push(VarData{
             var_id: channel_stmt.from,
             var_type: from_var_type,
             used_at: Vec::new(),
             linked_var: Some(to_var_index),
         });
         let to_local = &ctx.heap[channel_stmt.to];
         let to_var_type = self.determine_inference_type_from_parser_type_elements(&to_local.parser_type.elements, true);
         self.var_data.push(VarData{
             var_id: channel_stmt.to,
             var_type: to_var_type,
             used_at: Vec::new(),
             linked_var: Some(from_var_index),
         });
         Ok(())
+    }
     fn visit_labeled_stmt(&mut self, ctx: &mut Ctx, id: LabeledStatementId) -> VisitorResult {
         let labeled_stmt = &ctx.heap[id];
         let substmt_id = labeled_stmt.body;
         self.visit_stmt(ctx, substmt_id)
+    }
     fn visit_if_stmt(&mut self, ctx: &mut Ctx, id: IfStatementId) -> VisitorResult {
         let if_stmt = &ctx.heap[id];
         let true_body_case = if_stmt.true_case;
         let false_body_case = if_stmt.false_case;
         let test_expr_id = if_stmt.test;
         self.visit_expr(ctx, test_expr_id)?;
         self.visit_stmt(ctx, true_body_case.body)?;
         if let Some(false_body_case) = false_body_case {
             self.visit_stmt(ctx, false_body_case.body)?;
+        }
         Ok(())
+    }
     fn visit_while_stmt(&mut self, ctx: &mut Ctx, id: WhileStatementId) -> VisitorResult {
         let while_stmt = &ctx.heap[id];
         let body_id = while_stmt.body;
         let test_expr_id = while_stmt.test;
         self.visit_expr(ctx, test_expr_id)?;
         self.visit_stmt(ctx, body_id)?;
         Ok(())
+    }
     fn visit_break_stmt(&mut self, _: &mut Ctx, _: BreakStatementId) -> VisitorResult { return Ok(()) }
     fn visit_continue_stmt(&mut self, _: &mut Ctx, _: ContinueStatementId) -> VisitorResult { return Ok(()) }
     fn visit_synchronous_stmt(&mut self, ctx: &mut Ctx, id: SynchronousStatementId) -> VisitorResult {
         let sync_stmt = &ctx.heap[id];
         let body_id = sync_stmt.body;
         self.visit_stmt(ctx, body_id)
+    }
     fn visit_fork_stmt(&mut self, ctx: &mut Ctx, id: ForkStatementId) -> VisitorResult {
         let fork_stmt = &ctx.heap[id];
         let left_body_id = fork_stmt.left_body;
         let right_body_id = fork_stmt.right_body;
         self.visit_stmt(ctx, left_body_id)?;
         if let Some(right_body_id) = right_body_id {
             self.visit_stmt(ctx, right_body_id)?;
+        }
         Ok(())
+    }
     fn visit_select_stmt(&mut self, ctx: &mut Ctx, id: SelectStatementId) -> VisitorResult {
         let select_stmt = &ctx.heap[id];
         let mut section = self.stmt_buffer.start_section();
         let num_cases = select_stmt.cases.len();
         for case in &select_stmt.cases {
             section.push(case.guard);
             section.push(case.body);
+        }
         for case_index in 0..num_cases {
             let base_index = 2 * case_index;
             let guard_stmt_id = section[base_index    ];
             let block_stmt_id = section[base_index + 1];
             self.visit_stmt(ctx, guard_stmt_id)?;
             self.visit_stmt(ctx, block_stmt_id)?;
+        }
         section.forget();
         Ok(())
+    }
     fn visit_return_stmt(&mut self, ctx: &mut Ctx, id: ReturnStatementId) -> VisitorResult {
         let return_stmt = &ctx.heap[id];
         debug_assert_eq!(return_stmt.expressions.len(), 1);
         let expr_id = return_stmt.expressions[0];
         self.visit_expr(ctx, expr_id)?;
         return Ok(());
+    }
     fn visit_goto_stmt(&mut self, _: &mut Ctx, _: GotoStatementId) -> VisitorResult { return Ok(()) }
     fn visit_new_stmt(&mut self, ctx: &mut Ctx, id: NewStatementId) -> VisitorResult {
         let new_stmt = &ctx.heap[id];
         let call_expr_id = new_stmt.expression;
         self.visit_call_expr(ctx, call_expr_id)?;
         return Ok(());
+    }
     fn visit_expr_stmt(&mut self, ctx: &mut Ctx, id: ExpressionStatementId) -> VisitorResult {
         let expr_stmt = &ctx.heap[id];
         let subexpr_id = expr_stmt.expression;
         self.visit_expr(ctx, subexpr_id)?;
         return Ok(());
+    }
     // Expressions
     fn visit_expr(&mut self, ctx: &mut Ctx, id: ExpressionId) -> VisitExprResult {
         return visitor_recursive_expression_impl!(self, &ctx.heap[id], ctx);
+    }
     fn visit_assignment_expr(&mut self, ctx: &mut Ctx, id: AssignmentExpressionId) -> VisitExprResult {
         use AssignmentOperator as AO;
         let upcast_id = id.upcast();
         let self_index = self.insert_initial_inference_node(ctx, upcast_id)?;
         let assign_expr = &ctx.heap[id];
         let assign_op = assign_expr.operation;
         let left_expr_id = assign_expr.left;
         let right_expr_id = assign_expr.right;
         let old_parent = self.parent_index.replace(self_index);
         let left_index = self.visit_expr(ctx, left_expr_id)?;
         let right_index = self.visit_expr(ctx, right_expr_id)?;
         let node = &mut self.infer_nodes[self_index];
         let argument_template = match assign_op {
             AO::Set =>
                 InferenceRuleTemplate::new_none(),
             AO::Concatenated =>
                 InferenceRuleTemplate::new_template(&ARRAYLIKE_TEMPLATE),
             AO::Multiplied | AO::Divided | AO::Added | AO::Subtracted =>
                 InferenceRuleTemplate::new_template(&NUMBERLIKE_TEMPLATE),
             AO::Remained | AO::ShiftedLeft | AO::ShiftedRight |
             AO::BitwiseAnded | AO::BitwiseXored | AO::BitwiseOred =>
                 InferenceRuleTemplate::new_template(&INTEGERLIKE_TEMPLATE),
         };
         node.inference_rule = InferenceRule::TriEqualArgs(InferenceRuleTriEqualArgs{
             argument_template,
             result_template: InferenceRuleTemplate::new_forced(&VOID_TEMPLATE),
             argument1_index: left_index,
             argument2_index: right_index,
         });
         self.parent_index = old_parent;
         self.progress_inference_rule_tri_equal_args(ctx, self_index)?;
         return Ok(self_index);
+    }
     fn visit_binding_expr(&mut self, ctx: &mut Ctx, id: BindingExpressionId) -> VisitExprResult {
         let upcast_id = id.upcast();
         let self_index = self.insert_initial_inference_node(ctx, upcast_id)?;
         let binding_expr = &ctx.heap[id];
         let bound_to_id = binding_expr.bound_to;
         let bound_from_id = binding_expr.bound_from;
         let old_parent = self.parent_index.replace(self_index);
         let arg_to_index = self.visit_expr(ctx, bound_to_id)?;
         let arg_from_index = self.visit_expr(ctx, bound_from_id)?;
         let node = &mut self.infer_nodes[self_index];
         node.inference_rule = InferenceRule::TriEqualArgs(InferenceRuleTriEqualArgs{
             argument_template: InferenceRuleTemplate::new_none(),
             result_template: InferenceRuleTemplate::new_forced(&BOOL_TEMPLATE),
             argument1_index: arg_to_index,
             argument2_index: arg_from_index,
         });
         self.parent_index = old_parent;
         self.progress_inference_rule_tri_equal_args(ctx, self_index)?;
         return Ok(self_index);
+    }
     fn visit_conditional_expr(&mut self, ctx: &mut Ctx, id: ConditionalExpressionId) -> VisitExprResult {
         let upcast_id = id.upcast();
         let self_index = self.insert_initial_inference_node(ctx, upcast_id)?;
         let conditional_expr = &ctx.heap[id];
         let test_expr_id = conditional_expr.test;
         let true_expr_id = conditional_expr.true_expression;
         let false_expr_id = conditional_expr.false_expression;
         let old_parent = self.parent_index.replace(self_index);
         self.visit_expr(ctx, test_expr_id)?;
         let true_index = self.visit_expr(ctx, true_expr_id)?;
         let false_index = self.visit_expr(ctx, false_expr_id)?;
         // Note: the test to the conditional expression has already been forced
         // to the boolean type. So the only thing we need to do while progressing
         // is to apply an equal3 constraint to the arguments and the result of
         // the expression.
         let node = &mut self.infer_nodes[self_index];
         node.inference_rule = InferenceRule::TriEqualAll(InferenceRuleTriEqualAll{
             template: InferenceRuleTemplate::new_none(),
             argument1_index: true_index,
             argument2_index: false_index,
         });
         self.parent_index = old_parent;
         self.progress_inference_rule_tri_equal_all(ctx, self_index)?;
         return Ok(self_index);
+    }
     fn visit_binary_expr(&mut self, ctx: &mut Ctx, id: BinaryExpressionId) -> VisitExprResult {
         use BinaryOperator as BO;
         let upcast_id = id.upcast();
         let self_index = self.insert_initial_inference_node(ctx, upcast_id)?;
         let binary_expr = &ctx.heap[id];
         let binary_op = binary_expr.operation;
         let lhs_expr_id = binary_expr.left;
         let rhs_expr_id = binary_expr.right;
         let old_parent = self.parent_index.replace(self_index);
         let left_index = self.visit_expr(ctx, lhs_expr_id)?;
         let right_index = self.visit_expr(ctx, rhs_expr_id)?;
         let inference_rule = match binary_op {
             BO::Concatenate =>
                 InferenceRule::Concatenate(InferenceRuleTwoArgs{
                     argument1_index: left_index,
                     argument2_index: right_index,
                 }),
             BO::LogicalAnd | BO::LogicalOr =>
                 InferenceRule::TriEqualAll(InferenceRuleTriEqualAll{
                     template: InferenceRuleTemplate::new_forced(&BOOL_TEMPLATE),
                     argument1_index: left_index,
                     argument2_index: right_index,
                 }),
             BO::BitwiseOr | BO::BitwiseXor | BO::BitwiseAnd | BO::Remainder | BO::ShiftLeft | BO::ShiftRight =>
                 InferenceRule::TriEqualAll(InferenceRuleTriEqualAll{
                     template: InferenceRuleTemplate::new_template(&INTEGERLIKE_TEMPLATE),
                     argument1_index: left_index,
                     argument2_index: right_index,
                 }),
             BO::Equality | BO::Inequality =>
                 InferenceRule::TriEqualArgs(InferenceRuleTriEqualArgs{
                     argument_template: InferenceRuleTemplate::new_none(),
                     result_template: InferenceRuleTemplate::new_forced(&BOOL_TEMPLATE),
                     argument1_index: left_index,
                     argument2_index: right_index,
                 }),
             BO::LessThan | BO::GreaterThan | BO::LessThanEqual | BO::GreaterThanEqual =>
                 InferenceRule::TriEqualArgs(InferenceRuleTriEqualArgs{
                     argument_template: InferenceRuleTemplate::new_template(&NUMBERLIKE_TEMPLATE),
                     result_template: InferenceRuleTemplate::new_forced(&BOOL_TEMPLATE),
                     argument1_index: left_index,
                     argument2_index: right_index,
                 }),
             BO::Add | BO::Subtract | BO::Multiply | BO::Divide =>
                 InferenceRule::TriEqualAll(InferenceRuleTriEqualAll{
                     template: InferenceRuleTemplate::new_template(&NUMBERLIKE_TEMPLATE),
                     argument1_index: left_index,
                     argument2_index: right_index,
                 }),
         };
         let node = &mut self.infer_nodes[self_index];
         node.inference_rule = inference_rule;
         self.parent_index = old_parent;
         self.progress_inference_rule(ctx, self_index)?;
         return Ok(self_index);
+    }
     fn visit_unary_expr(&mut self, ctx: &mut Ctx, id: UnaryExpressionId) -> VisitExprResult {
         use UnaryOperator as UO;
         let upcast_id = id.upcast();
         let self_index = self.insert_initial_inference_node(ctx, upcast_id)?;
         let unary_expr = &ctx.heap[id];
         let operation = unary_expr.operation;
         let arg_expr_id = unary_expr.expression;
         let old_parent = self.parent_index.replace(self_index);
         let argument_index = self.visit_expr(ctx, arg_expr_id)?;
         let template = match operation {
             UO::Positive | UO::Negative =>
                 InferenceRuleTemplate::new_template(&NUMBERLIKE_TEMPLATE),
             UO::BitwiseNot =>
                 InferenceRuleTemplate::new_template(&INTEGERLIKE_TEMPLATE),
             UO::LogicalNot =>
                 InferenceRuleTemplate::new_forced(&BOOL_TEMPLATE),
         };
         let node = &mut self.infer_nodes[self_index];
         node.inference_rule = InferenceRule::BiEqual(InferenceRuleBiEqual{
             template, argument_index,
         });
         self.parent_index = old_parent;
         self.progress_inference_rule_bi_equal(ctx, self_index)?;
         return Ok(self_index);
+    }
     fn visit_indexing_expr(&mut self, ctx: &mut Ctx, id: IndexingExpressionId) -> VisitExprResult {
         let upcast_id = id.upcast();
         let self_index = self.insert_initial_inference_node(ctx, upcast_id)?;
         let indexing_expr = &ctx.heap[id];
         let subject_expr_id = indexing_expr.subject;
         let index_expr_id = indexing_expr.index;
         let old_parent = self.parent_index.replace(self_index);
         let subject_index = self.visit_expr(ctx, subject_expr_id)?;
         let index_index = self.visit_expr(ctx, index_expr_id)?; // cool name, bro
         let node = &mut self.infer_nodes[self_index];
         node.inference_rule = InferenceRule::IndexingExpr(InferenceRuleIndexingExpr{
             subject_index, index_index,
         });
         self.parent_index = old_parent;
         self.progress_inference_rule_indexing_expr(ctx, self_index)?;
         return Ok(self_index);
+    }
     fn visit_slicing_expr(&mut self, ctx: &mut Ctx, id: SlicingExpressionId) -> VisitExprResult {
         let upcast_id = id.upcast();
         let self_index = self.insert_initial_inference_node(ctx, upcast_id)?;
         let slicing_expr = &ctx.heap[id];
         let subject_expr_id = slicing_expr.subject;
         let from_expr_id = slicing_expr.from_index;
         let to_expr_id = slicing_expr.to_index;
         let old_parent = self.parent_index.replace(self_index);
         let subject_index = self.visit_expr(ctx, subject_expr_id)?;
         let from_index = self.visit_expr(ctx, from_expr_id)?;
         let to_index = self.visit_expr(ctx, to_expr_id)?;
         let node = &mut self.infer_nodes[self_index];
         node.inference_rule = InferenceRule::SlicingExpr(InferenceRuleSlicingExpr{
             subject_index, from_index, to_index,
         });
         self.parent_index = old_parent;
         self.progress_inference_rule_slicing_expr(ctx, self_index)?;
         return Ok(self_index);
+    }
     fn visit_select_expr(&mut self, ctx: &mut Ctx, id: SelectExpressionId) -> VisitExprResult {
         let upcast_id = id.upcast();
         let self_index = self.insert_initial_inference_node(ctx, upcast_id)?;
         let select_expr = &ctx.heap[id];
         let subject_expr_id = select_expr.subject;
         let old_parent = self.parent_index.replace(self_index);
         let subject_index = self.visit_expr(ctx, subject_expr_id)?;
         let node = &mut self.infer_nodes[self_index];
         let inference_rule = match &ctx.heap[id].kind {
             SelectKind::StructField(field_identifier) =>
                 InferenceRule::SelectStructField(InferenceRuleSelectStructField{
                     subject_index,
                     selected_field: field_identifier.clone(),
                 }),
             SelectKind::TupleMember(member_index) =>
                 InferenceRule::SelectTupleMember(InferenceRuleSelectTupleMember{
                     subject_index,
                     selected_index: *member_index,
                 }),
         };
         node.inference_rule = inference_rule;
         self.parent_index = old_parent;
         self.progress_inference_rule(ctx, self_index)?;
         return Ok(self_index);
+    }
     fn visit_literal_expr(&mut self, ctx: &mut Ctx, id: LiteralExpressionId) -> VisitExprResult {
         let upcast_id = id.upcast();
         let self_index = self.insert_initial_inference_node(ctx, upcast_id)?;
         let old_parent = self.parent_index.replace(self_index);
         let literal_expr = &ctx.heap[id];
         match &literal_expr.value {
             Literal::Null => {
                 let node = &mut self.infer_nodes[self_index];
                 node.inference_rule = InferenceRule::MonoTemplate(InferenceRuleTemplate::new_template(&MESSAGE_TEMPLATE));
             },
             Literal::Integer(_) => {
                 let node = &mut self.infer_nodes[self_index];
                 node.inference_rule = InferenceRule::MonoTemplate(InferenceRuleTemplate::new_template(&INTEGERLIKE_TEMPLATE));
             },
             Literal::True | Literal::False => {
                 let node = &mut self.infer_nodes[self_index];
                 node.inference_rule = InferenceRule::MonoTemplate(InferenceRuleTemplate::new_forced(&BOOL_TEMPLATE));
             },
             Literal::Character(_) => {
                 let node = &mut self.infer_nodes[self_index];
                 node.inference_rule = InferenceRule::MonoTemplate(InferenceRuleTemplate::new_forced(&CHARACTER_TEMPLATE));
             },
             Literal::String(_) => {
                 let node = &mut self.infer_nodes[self_index];
                 node.inference_rule = InferenceRule::MonoTemplate(InferenceRuleTemplate::new_forced(&STRING_TEMPLATE));
             },
             Literal::Struct(literal) => {
                 // Visit field expressions
                 let mut expr_ids = self.expr_buffer.start_section();
                 for field in &literal.fields {
                     expr_ids.push(field.value);
+                }
                 let mut expr_indices = self.index_buffer.start_section();
                 for expr_id in expr_ids.iter_copied() {
                     let expr_index = self.visit_expr(ctx, expr_id)?;
                     expr_indices.push(expr_index);
+                }
                 expr_ids.forget();
                 let element_indices = expr_indices.into_vec();
                 // Assign rule and extra data index to inference node
                 let poly_data_index = self.insert_initial_struct_polymorph_data(ctx, id);
                 let node = &mut self.infer_nodes[self_index];
                 node.poly_data_index = poly_data_index;
                 node.inference_rule = InferenceRule::LiteralStruct(InferenceRuleLiteralStruct{
                     element_indices,
                 });
             },
             Literal::Enum(_) => {
                 // Enumerations do not carry any subexpressions, but may still
                 // have a user-defined polymorphic marker variable. For this
                 // reason we may still have to apply inference to this
                 // polymorphic variable
                 let poly_data_index = self.insert_initial_enum_polymorph_data(ctx, id);
                 let node = &mut self.infer_nodes[self_index];
                 node.poly_data_index = poly_data_index;
                 node.inference_rule = InferenceRule::LiteralEnum;
             },
             Literal::Union(literal) => {
                 // May carry subexpressions and polymorphic arguments
                 let expr_ids = self.expr_buffer.start_section_initialized(literal.values.as_slice());
                 let poly_data_index = self.insert_initial_union_polymorph_data(ctx, id);
                 let mut expr_indices = self.index_buffer.start_section();
                 for expr_id in expr_ids.iter_copied() {
                     let expr_index = self.visit_expr(ctx, expr_id)?;
                     expr_indices.push(expr_index);
+                }
                 expr_ids.forget();
                 let element_indices = expr_indices.into_vec();
                 let node = &mut self.infer_nodes[self_index];
                 node.poly_data_index = poly_data_index;
                 node.inference_rule = InferenceRule::LiteralUnion(InferenceRuleLiteralUnion{
                     element_indices,
                 });
             },
             Literal::Array(expressions) => {
                 let expr_ids = self.expr_buffer.start_section_initialized(expressions.as_slice());
                 let mut expr_indices = self.index_buffer.start_section();
                 for expr_id in expr_ids.iter_copied() {
                     let expr_index = self.visit_expr(ctx, expr_id)?;
                     expr_indices.push(expr_index);
+                }
                 expr_ids.forget();
                 let element_indices = expr_indices.into_vec();
                 let node = &mut self.infer_nodes[self_index];
                 node.inference_rule = InferenceRule::LiteralArray(InferenceRuleLiteralArray{
                     element_indices,
                 });
             },
             Literal::Tuple(expressions) => {
                 let expr_ids = self.expr_buffer.start_section_initialized(expressions.as_slice());
                 let mut expr_indices = self.index_buffer.start_section();
                 for expr_id in expr_ids.iter_copied() {
                     let expr_index = self.visit_expr(ctx, expr_id)?;
                     expr_indices.push(expr_index);
+                }
                 expr_ids.forget();
                 let element_indices = expr_indices.into_vec();
                 let node = &mut self.infer_nodes[self_index];
                 node.inference_rule = InferenceRule::LiteralTuple(InferenceRuleLiteralTuple{
                     element_indices,
                 })
+            }
+        }
         self.parent_index = old_parent;
         self.progress_inference_rule(ctx, self_index)?;
         return Ok(self_index);
+    }
     fn visit_cast_expr(&mut self, ctx: &mut Ctx, id: CastExpressionId) -> VisitExprResult {
         let upcast_id = id.upcast();
         let self_index = self.insert_initial_inference_node(ctx, upcast_id)?;
         let cast_expr = &ctx.heap[id];
         let subject_expr_id = cast_expr.subject;
         let old_parent = self.parent_index.replace(self_index);
         let subject_index = self.visit_expr(ctx, subject_expr_id)?;
         let node = &mut self.infer_nodes[self_index];
         node.inference_rule = InferenceRule::CastExpr(InferenceRuleCastExpr{
             subject_index,
         });
         self.parent_index = old_parent;
         // The cast expression is a bit special at this point: the progression
         // function simply makes sure input/output types are compatible. But if
         // the programmer explicitly specified the output type, then we can
         // already perform that inference rule here.
+        {
             let cast_expr = &ctx.heap[id];
             let specified_type = self.determine_inference_type_from_parser_type_elements(&cast_expr.to_type.elements, true);
             let _progress = self.apply_template_constraint(ctx, self_index, &specified_type.parts)?;
+        }
         self.progress_inference_rule_cast_expr(ctx, self_index)?;
         return Ok(self_index);
+    }
     fn visit_call_expr(&mut self, ctx: &mut Ctx, id: CallExpressionId) -> VisitExprResult {
         let upcast_id = id.upcast();
         let self_index = self.insert_initial_inference_node(ctx, upcast_id)?;
         let extra_index = self.insert_initial_call_polymorph_data(ctx, id);
         // By default we set the polymorph idx for calls to 0. If the call
         // refers to a non-polymorphic function, then it will be "monomorphed"
         // once, hence we end up pointing to the correct instance.
         self.infer_nodes[self_index].field_index = 0;
         // Visit all arguments
         let old_parent = self.parent_index.replace(self_index);
         let call_expr = &ctx.heap[id];
         let expr_ids = self.expr_buffer.start_section_initialized(call_expr.arguments.as_slice());
         let mut expr_indices = self.index_buffer.start_section();
         for arg_expr_id in expr_ids.iter_copied() {
             let expr_index = self.visit_expr(ctx, arg_expr_id)?;
             expr_indices.push(expr_index);
+        }
         expr_ids.forget();
         let argument_indices = expr_indices.into_vec();
         let node = &mut self.infer_nodes[self_index];
         node.poly_data_index = extra_index;
         node.inference_rule = InferenceRule::CallExpr(InferenceRuleCallExpr{
             argument_indices,
         });
         self.parent_index = old_parent;
         self.progress_inference_rule_call_expr(ctx, self_index)?;
         return Ok(self_index);
+    }
     fn visit_variable_expr(&mut self, ctx: &mut Ctx, id: VariableExpressionId) -> VisitExprResult {
         let upcast_id = id.upcast();
         let self_index = self.insert_initial_inference_node(ctx, upcast_id)?;
         let var_expr = &ctx.heap[id];
         debug_assert!(var_expr.declaration.is_some());
         let old_parent = self.parent_index.replace(self_index);
         let declaration = &ctx.heap[var_expr.declaration.unwrap()];
         let mut var_data_index = None;
         for (index, var_data) in self.var_data.iter().enumerate() {
             if var_data.var_id == declaration.this {
                 var_data_index = Some(index);
                 break;
+            }
+        }
         let var_data_index = if let Some(var_data_index) = var_data_index {
             let var_data = &mut self.var_data[var_data_index];
             var_data.used_at.push(self_index);
             var_data_index
         } else {
             // If we're in a binding expression then it might the first time we
             // encounter the variable, so add a `VarData` entry.
             debug_assert_eq!(declaration.kind, VariableKind::Binding);
             let var_type = self.determine_inference_type_from_parser_type_elements(
                 &declaration.parser_type.elements, true
             );
             let var_data_index = self.var_data.len();
             self.var_data.push(VarData{
                 var_id: declaration.this,
                 var_type,
                 used_at: vec![self_index],
                 linked_var: None,
             });
             var_data_index
         };
         let node = &mut self.infer_nodes[self_index];
         node.inference_rule = InferenceRule::VariableExpr(InferenceRuleVariableExpr{
             var_data_index,
         });
         self.parent_index = old_parent;
         self.progress_inference_rule_variable_expr(ctx, self_index)?;
         return Ok(self_index);
+    }
+}
 // -----------------------------------------------------------------------------
 // PassTyping - Type-inference progression
 // -----------------------------------------------------------------------------
 impl PassTyping {
     #[allow(dead_code)] // used when debug flag at the top of this file is true.
     fn debug_get_display_name(&self, ctx: &Ctx, node_index: InferNodeIndex) -> String {
         let expr_type = &self.infer_nodes[node_index].expr_type;
         expr_type.display_name(&ctx.heap)
+    }
     fn resolve_types(&mut self, ctx: &mut Ctx, queue: &mut ResolveQueue) -> Result<(), ParseError> {
         // Keep inferring until we can no longer make any progress
         while !self.node_queued.is_empty() {
             while !self.node_queued.is_empty() {
                 let node_index = self.node_queued.pop_front().unwrap();
                 self.progress_inference_rule(ctx, node_index)?;
+            }
             // Nothing is queued anymore. However we might have integer literals
             // whose type cannot be inferred. For convenience's sake we'll
             // infer these to be s32.
             for (infer_node_index, infer_node) in self.infer_nodes.iter_mut().enumerate() {
                 let expr_type = &mut infer_node.expr_type;
                 if !expr_type.is_done && expr_type.parts.len() == 1 && expr_type.parts[0] == InferenceTypePart::IntegerLike {
                     // Force integer type to s32
                     expr_type.parts[0] = InferenceTypePart::SInt32;
                     expr_type.is_done = true;
                     // Requeue expression (and its parent, if it exists)
                     self.node_queued.push_back(infer_node_index);
                     if let Some(node_parent_index) = infer_node.parent_index {
                         self.node_queued.push_back(node_parent_index);
+                    }
+                }
+            }
+        }
         // Helper for transferring polymorphic variables to concrete types and
         // checking if they're completely specified
         fn poly_data_type_to_concrete_type(
             ctx: &Ctx, expr_id: ExpressionId, inference_poly_args: &Vec<InferenceType>,
             first_concrete_part: ConcreteTypePart,
         ) -> Result<ConcreteType, ParseError> {
             // Prepare storage vector
             let mut num_inference_parts = 0;
             for inference_type in inference_poly_args {
                 num_inference_parts += inference_type.parts.len();
+            }
             let mut concrete_type = ConcreteType{
                 parts: Vec::with_capacity(1 + num_inference_parts),
             };
             concrete_type.parts.push(first_concrete_part);
             // Go through all polymorphic arguments and add them to the concrete
             // types.
             for (poly_idx, poly_type) in inference_poly_args.iter().enumerate() {
                 if !poly_type.is_done {
                     let expr = &ctx.heap[expr_id];
                     let definition = match expr {
                         Expression::Call(expr) => expr.procedure.upcast(),
                         Expression::Literal(expr) => match &expr.value {
                             Literal::Enum(lit) => lit.definition,
                             Literal::Union(lit) => lit.definition,
                             Literal::Struct(lit) => lit.definition,
                             _ => unreachable!()
                         },
                         _ => unreachable!(),
                     };
                     let poly_vars = ctx.heap[definition].poly_vars();
                     return Err(ParseError::new_error_at_span(
                         &ctx.module().source, expr.operation_span(), format!(
                             "could not fully infer the type of polymorphic variable '{}' of this expression (got '{}')",
                             poly_vars[poly_idx].value.as_str(), poly_type.display_name(&ctx.heap)
+                        )
                     ));
+                }
                 poly_type.write_concrete_type(&mut concrete_type);
+            }
             Ok(concrete_type)
+        }
         // Every expression checked, and new monomorphs are queued. Transfer the
         // expression information to the AST. If this is the first time we're
         // visiting this procedure then we assign expression indices as well.
         let procedure = &ctx.heap[self.procedure_id];
         let num_infer_nodes = self.infer_nodes.len();
         let mut monomorph = ProcedureDefinitionMonomorph{
             argument_types: Vec::with_capacity(procedure.parameters.len()),
             expr_info: Vec::with_capacity(num_infer_nodes),
         };
         // For all of the expressions look up the TypeId (or create a new one).
         // For function calls and component instantiations figure out if they
         // need to be typechecked
         for infer_node in self.infer_nodes.iter_mut() {
             // Determine type ID
             let expr = &ctx.heap[infer_node.expr_id];
             // TODO: Maybe optimize? Split insertion up into lookup, then clone
             //  if needed?
             let mut concrete_type = ConcreteType::default();
             infer_node.expr_type.write_concrete_type(&mut concrete_type);
             let info_type_id = ctx.types.add_monomorphed_type(ctx.modules, ctx.heap, ctx.arch, concrete_type)?;
             // Determine procedure type ID, i.e. a called/instantiated
             // procedure's signature.
             let info_variant = if let Expression::Call(expr) = expr {
                 // Construct full function type. If not yet typechecked then
                 // queue it for typechecking.
                 let poly_data = &self.poly_data[infer_node.poly_data_index as usize];
                 debug_assert!(expr.method.is_user_defined() || expr.method.is_public_builtin());
                 let procedure_id = expr.procedure;
                 let num_poly_vars = poly_data.poly_vars.len() as u32;
                 let first_part = match expr.method {
                     Method::UserFunction => ConcreteTypePart::Function(procedure_id, num_poly_vars),
                     Method::UserComponent => ConcreteTypePart::Component(procedure_id, num_poly_vars),
                     _ => ConcreteTypePart::Function(procedure_id, num_poly_vars),
                 };
                 let definition_id = procedure_id.upcast();
                 let signature_type = poly_data_type_to_concrete_type(
                     ctx, infer_node.expr_id, &poly_data.poly_vars, first_part
                 )?;
                 let (type_id, monomorph_index) = if let Some(type_id) = ctx.types.get_procedure_monomorph_type_id(&definition_id, &signature_type.parts) {
                     // Procedure is already typechecked
                     let monomorph_index = ctx.types.get_monomorph(type_id).variant.as_procedure().monomorph_index;
                     (type_id, monomorph_index)
                 } else {
                     // Procedure is not yet typechecked, reserve a TypeID and a monomorph index
                     let procedure_to_check = &mut ctx.heap[procedure_id];
                     let monomorph_index = procedure_to_check.monomorphs.len() as u32;
                     procedure_to_check.monomorphs.push(ProcedureDefinitionMonomorph::new_invalid());
                     let type_id = ctx.types.reserve_procedure_monomorph_type_id(&definition_id, signature_type, monomorph_index);
                     queue.push(ResolveQueueElement{
                         root_id: ctx.heap[definition_id].defined_in(),
                         definition_id,
                         reserved_type_id: type_id,
                         reserved_monomorph_index: monomorph_index,
                     });
                     if !procedure_to_check.builtin {
                         // Only perform typechecking on the user-defined
                         // procedures
                         queue.push_back(ResolveQueueElement{
                             root_id: ctx.heap[definition_id].defined_in(),
                             definition_id,
                             reserved_type_id: type_id,
                             reserved_monomorph_index: monomorph_index,
                         });
+                    }
                     (type_id, monomorph_index)
                 };
                 ExpressionInfoVariant::Procedure(type_id, monomorph_index)
             } else if let Expression::Select(_expr) = expr {
                 ExpressionInfoVariant::Select(infer_node.field_index)
             } else {
                 ExpressionInfoVariant::Generic
             };
             infer_node.info_type_id = info_type_id;
             infer_node.info_variant = info_variant;
+        }
         // Write the types of the arguments
         let procedure = &ctx.heap[self.procedure_id];
         for parameter_id in procedure.parameters.iter().copied() {
             let mut concrete = ConcreteType::default();
             let var_data = self.var_data.iter().find(|v| v.var_id == parameter_id).unwrap();
             var_data.var_type.write_concrete_type(&mut concrete);
             let type_id = ctx.types.add_monomorphed_type(ctx.modules, ctx.heap, ctx.arch, concrete)?;
             monomorph.argument_types.push(type_id)
+        }
         println!("DEBUG: For procedure {} with polyargs {:#?}", ctx.heap[self.procedure_id].identifier.value.as_str(), self.poly_vars);
         for infer_node in self.infer_nodes.iter() {
             println!("DEBUG: [{:?}] has type: {}", infer_node.expr_id, infer_node.expr_type.display_name(&ctx.heap));
+        }
         // Determine if we have already assigned type indices to the expressions
         // before (the indices that, for a monomorph, can retrieve the type of
         // the expression).
         let has_type_indices = self.reserved_monomorph_index > 0;
         if has_type_indices {
             // already have indices, so resize and then index into it
             debug_assert!(monomorph.expr_info.is_empty());
             monomorph.expr_info.resize(num_infer_nodes, ExpressionInfo::new_invalid());
             for infer_node in self.infer_nodes.iter() {
                 let type_index = ctx.heap[infer_node.expr_id].type_index();
                 monomorph.expr_info[type_index as usize] = infer_node.as_expression_info();
+            }
         } else {
             // no indices yet, need to be assigned in AST
             for infer_node in self.infer_nodes.iter() {
                 let type_index = monomorph.expr_info.len();
                 monomorph.expr_info.push(infer_node.as_expression_info());
                 *ctx.heap[infer_node.expr_id].type_index_mut() = type_index as i32;
+            }
+        }
         // Push the information into the AST
         let procedure = &mut ctx.heap[self.procedure_id];
         procedure.monomorphs[self.reserved_monomorph_index as usize] = monomorph;
         Ok(())
+    }
     fn progress_inference_rule(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         use InferenceRule as IR;
         let node = &self.infer_nodes[node_index];
         match &node.inference_rule {
             IR::Noop =>
                 unreachable!(),
             IR::MonoTemplate(_) =>
                 self.progress_inference_rule_mono_template(ctx, node_index),
             IR::BiEqual(_) =>
                 self.progress_inference_rule_bi_equal(ctx, node_index),
             IR::TriEqualArgs(_) =>
                 self.progress_inference_rule_tri_equal_args(ctx, node_index),
             IR::TriEqualAll(_) =>
                 self.progress_inference_rule_tri_equal_all(ctx, node_index),
             IR::Concatenate(_) =>
                 self.progress_inference_rule_concatenate(ctx, node_index),
             IR::IndexingExpr(_) =>
                 self.progress_inference_rule_indexing_expr(ctx, node_index),
             IR::SlicingExpr(_) =>
                 self.progress_inference_rule_slicing_expr(ctx, node_index),
             IR::SelectStructField(_) =>
                 self.progress_inference_rule_select_struct_field(ctx, node_index),
             IR::SelectTupleMember(_) =>
                 self.progress_inference_rule_select_tuple_member(ctx, node_index),
             IR::LiteralStruct(_) =>
                 self.progress_inference_rule_literal_struct(ctx, node_index),
             IR::LiteralEnum =>
                 self.progress_inference_rule_literal_enum(ctx, node_index),
             IR::LiteralUnion(_) =>
                 self.progress_inference_rule_literal_union(ctx, node_index),
             IR::LiteralArray(_) =>
                 self.progress_inference_rule_literal_array(ctx, node_index),
             IR::LiteralTuple(_) =>
                 self.progress_inference_rule_literal_tuple(ctx, node_index),
             IR::CastExpr(_) =>
                 self.progress_inference_rule_cast_expr(ctx, node_index),
             IR::CallExpr(_) =>
                 self.progress_inference_rule_call_expr(ctx, node_index),
             IR::VariableExpr(_) =>
                 self.progress_inference_rule_variable_expr(ctx, node_index),
+        }
+    }
     fn progress_inference_rule_mono_template(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let rule = *node.inference_rule.as_mono_template();
         let progress = self.progress_template(ctx, node_index, rule.application, rule.template)?;
         if progress { self.queue_node_parent(node_index); }
         return Ok(());
+    }
     fn progress_inference_rule_bi_equal(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let rule = node.inference_rule.as_bi_equal();
         let template = rule.template;
         let arg_index = rule.argument_index;
         let base_progress = self.progress_template(ctx, node_index, template.application, template.template)?;
         let (node_progress, arg_progress) = self.apply_equal2_constraint(ctx, node_index, node_index, 0, arg_index, 0)?;
         if base_progress || node_progress { self.queue_node_parent(node_index); }
         if arg_progress { self.queue_node(arg_index); }
         return Ok(())
+    }
     fn progress_inference_rule_tri_equal_args(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let rule = node.inference_rule.as_tri_equal_args();
         let result_template = rule.result_template;
         let argument_template = rule.argument_template;
         let arg1_index = rule.argument1_index;
         let arg2_index = rule.argument2_index;
         let self_template_progress = self.progress_template(ctx, node_index, result_template.application, result_template.template)?;
         let arg1_template_progress = self.progress_template(ctx, arg1_index, argument_template.application, argument_template.template)?;
         let (arg1_progress, arg2_progress) = self.apply_equal2_constraint(ctx, node_index, arg1_index, 0, arg2_index, 0)?;
         if self_template_progress { self.queue_node_parent(node_index); }
         if arg1_template_progress || arg1_progress { self.queue_node(arg1_index); }
         if arg2_progress { self.queue_node(arg2_index); }
         return Ok(());
+    }
     fn progress_inference_rule_tri_equal_all(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let rule = node.inference_rule.as_tri_equal_all();
         let template = rule.template;
         let arg1_index = rule.argument1_index;
         let arg2_index = rule.argument2_index;
         let template_progress = self.progress_template(ctx, node_index, template.application, template.template)?;
         let (node_progress, arg1_progress, arg2_progress) =
             self.apply_equal3_constraint(ctx, node_index, arg1_index, arg2_index, 0)?;
         if template_progress || node_progress { self.queue_node_parent(node_index); }
         if arg1_progress { self.queue_node(arg1_index); }
         if arg2_progress { self.queue_node(arg2_index); }
         return Ok(());
+    }
     fn progress_inference_rule_concatenate(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let rule = node.inference_rule.as_concatenate();
         let arg1_index = rule.argument1_index;
         let arg2_index = rule.argument2_index;
         // Two cases: one of the arguments is a string (then all must be), or
         // one of the arguments is an array (and all must be arrays).
         let (expr_is_str, expr_is_not_str) = self.type_is_certainly_or_certainly_not_string(node_index);
         let (arg1_is_str, arg1_is_not_str) = self.type_is_certainly_or_certainly_not_string(arg1_index);
         let (arg2_is_str, arg2_is_not_str) = self.type_is_certainly_or_certainly_not_string(arg2_index);
         let someone_is_str = expr_is_str || arg1_is_str || arg2_is_str;
         let someone_is_not_str = expr_is_not_str || arg1_is_not_str || arg2_is_not_str;
         // Note: this statement is an expression returning the progression bools
         let (node_progress, arg1_progress, arg2_progress) = if someone_is_str {
             // One of the arguments is a string, then all must be strings
             self.apply_equal3_constraint(ctx, node_index, arg1_index, arg2_index, 0)?
         } else {
             let progress_expr = if someone_is_not_str {
                 // Output must be a normal array
                 self.apply_template_constraint(ctx, node_index, &ARRAY_TEMPLATE)?
             } else {
                 // Output may still be anything
                 self.apply_template_constraint(ctx, node_index, &ARRAYLIKE_TEMPLATE)?
             };
             let progress_arg1 = self.apply_template_constraint(ctx, arg1_index, &ARRAYLIKE_TEMPLATE)?;
             let progress_arg2 = self.apply_template_constraint(ctx, arg2_index, &ARRAYLIKE_TEMPLATE)?;
             // If they're all arraylike, then we want the subtype to match
             let (subtype_expr, subtype_arg1, subtype_arg2) =
                 self.apply_equal3_constraint(ctx, node_index, arg1_index, arg2_index, 1)?;
             (progress_expr || subtype_expr, progress_arg1 || subtype_arg1, progress_arg2 || subtype_arg2)
         };
         if node_progress { self.queue_node_parent(node_index); }
         if arg1_progress { self.queue_node(arg1_index); }
         if arg2_progress { self.queue_node(arg2_index); }
         return Ok(())
+    }
     fn progress_inference_rule_indexing_expr(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let rule = node.inference_rule.as_indexing_expr();
         let subject_index = rule.subject_index;
         let index_index = rule.index_index; // which one?
         // Subject is arraylike, index in integerlike
         let subject_template_progress = self.apply_template_constraint(ctx, subject_index, &ARRAYLIKE_TEMPLATE)?;
         let index_template_progress = self.apply_template_constraint(ctx, index_index, &INTEGERLIKE_TEMPLATE)?;
         // If subject is type `Array<T>`, then expr type is `T`
         let (node_progress, subject_progress) =
             self.apply_equal2_constraint(ctx, node_index, node_index, 0, subject_index, 1)?;
         if node_progress { self.queue_node_parent(node_index); }
         if subject_template_progress || subject_progress { self.queue_node(subject_index); }
         if index_template_progress { self.queue_node(index_index); }
         return Ok(());
+    }
     fn progress_inference_rule_slicing_expr(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let rule = node.inference_rule.as_slicing_expr();
         let subject_index = rule.subject_index;
         let from_index_index = rule.from_index;
         let to_index_index = rule.to_index;
         debug_log!("Rule slicing [node: {}, expr: {}]", node_index, node.expr_id.index);
         // Subject is arraylike, indices are integerlike
         let subject_template_progress = self.apply_template_constraint(ctx, subject_index, &ARRAYLIKE_TEMPLATE)?;
         let from_template_progress = self.apply_template_constraint(ctx, from_index_index, &INTEGERLIKE_TEMPLATE)?;
         let to_template_progress = self.apply_template_constraint(ctx, to_index_index, &INTEGERLIKE_TEMPLATE)?;
         let (from_index_progress, to_index_progress) =
             self.apply_equal2_constraint(ctx, node_index, from_index_index, 0, to_index_index, 0)?;
         // Same as array indexing: result depends on whether subject is string
         // or array
         let (is_string, is_not_string) = self.type_is_certainly_or_certainly_not_string(node_index);
         let (node_progress, subject_progress) = if is_string {
             // Certainly a string
+            (
                 self.apply_forced_constraint(ctx, node_index, &STRING_TEMPLATE)?,
                 false
+            )
         } else if is_not_string {
             // Certainly not a string, apply template constraint. Then make sure
             // that if we have an `Array<T>`, that the slice produces `Slice<T>`
             let node_template_progress = self.apply_template_constraint(ctx, node_index, &SLICE_TEMPLATE)?;
             let (node_progress, subject_progress) =
                 self.apply_equal2_constraint(ctx, node_index, node_index, 1, subject_index, 1)?;
+            (
                 node_template_progress || node_progress,
                 subject_progress
+            )
         } else {
             // Not sure yet
             let node_template_progress = self.apply_template_constraint(ctx, node_index, &ARRAYLIKE_TEMPLATE)?;
             let (node_progress, subject_progress) =
                 self.apply_equal2_constraint(ctx, node_index, node_index, 1, subject_index, 1)?;
+            (
                 node_template_progress || node_progress,
                 subject_progress
+            )
         };
         if node_progress { self.queue_node_parent(node_index); }
         if subject_template_progress || subject_progress { self.queue_node(subject_index); }
         if from_template_progress || from_index_progress { self.queue_node(from_index_index); }
         if to_template_progress || to_index_progress { self.queue_node(to_index_index); }
         return Ok(());
+    }
     fn progress_inference_rule_select_struct_field(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let rule = node.inference_rule.as_select_struct_field();
         let subject_index = rule.subject_index;
         let selected_field = rule.selected_field.clone();
         fn get_definition_id_from_inference_type(inference_type: &InferenceType) -> Result<Option<DefinitionId>, ()> {
             for part in inference_type.parts.iter() {
                 if part.is_marker() { continue; }
                 if !part.is_concrete() { break; }
                 if let InferenceTypePart::Instance(definition_id, _) = part {
                     return Ok(Some(*definition_id));
                 } else {
                     return Err(())
+                }
+            }
             // Nothing is known yet
             return Ok(None);
+        }
         if node.field_index < 0 {
             // Don't know the subject definition, hence the field yet. Try to
             // determine it.
             let subject_node = &self.infer_nodes[subject_index];
             match get_definition_id_from_inference_type(&subject_node.expr_type) {
                 Ok(Some(definition_id)) => {
                     // Determined definition of subject for the first time.
                     let base_definition = ctx.types.get_base_definition(&definition_id).unwrap();
                     let struct_definition = if let DefinedTypeVariant::Struct(struct_definition) = &base_definition.definition {
                         struct_definition
                     } else {
                         return Err(ParseError::new_error_at_span(
                             &ctx.module().source, selected_field.span, format!(
                                 "Can only apply field access to structs, got a subject of type '{}'",
                                 subject_node.expr_type.display_name(&ctx.heap)
+                            )
                         ));
                     };
                     // Seek the field that is referenced by the select
                     // expression
                     let mut field_found = false;
                     for (field_index, field) in struct_definition.fields.iter().enumerate() {
                         if field.identifier.value == selected_field.value {
                             // Found the field of interest
                             field_found = true;
                             let node = &mut self.infer_nodes[node_index];
                             node.field_index = field_index as i32;
                             break;
+                        }
+                    }
                     if !field_found {
                         let struct_definition = ctx.heap[definition_id].as_struct();
                         return Err(ParseError::new_error_at_span(
                             &ctx.module().source, selected_field.span, format!(
                                 "this field does not exist on the struct '{}'",
                                 struct_definition.identifier.value.as_str()
+                            )
                         ));
+                    }
                     // Insert the initial data needed to infer polymorphic
                     // fields
                     let extra_index = self.insert_initial_select_polymorph_data(ctx, node_index, definition_id);
                     let node = &mut self.infer_nodes[node_index];
                     node.poly_data_index = extra_index;
                 },
                 Ok(None) => {
                     // We don't know what to do yet, because we don't know the
                     // subject type yet.
                     return Ok(())
                 },
                 Err(()) => {
                     return Err(ParseError::new_error_at_span(
                         &ctx.module().source, rule.selected_field.span, format!(
                             "Can only apply field access to structs, got a subject of type '{}'",
                             subject_node.expr_type.display_name(&ctx.heap)
+                        )
                     ));
                 },
+            }
+        }
         // If here then the field index is known, hence we can start inferring
         // the type of the selected field
         let field_expr_id = self.infer_nodes[node_index].expr_id;
         let subject_expr_id = self.infer_nodes[subject_index].expr_id;
         let mut poly_progress_section = self.poly_progress_buffer.start_section();
         let (_, progress_subject_1) = self.apply_polydata_equal2_constraint(
             ctx, node_index, subject_expr_id, "selected struct's",
             PolyDataTypeIndex::Associated(0), 0, subject_index, 0, &mut poly_progress_section
         )?;
         let (_, progress_field_1) = self.apply_polydata_equal2_constraint(
             ctx, node_index, field_expr_id, "selected field's",
             PolyDataTypeIndex::Returned, 0, node_index, 0, &mut poly_progress_section
         )?;
         // Maybe make progress on types due to inferred polymorphic variables
         let progress_subject_2 = self.apply_polydata_polyvar_constraint(
             ctx, node_index, PolyDataTypeIndex::Associated(0), subject_index, &poly_progress_section
         );
         let progress_field_2 = self.apply_polydata_polyvar_constraint(
             ctx, node_index, PolyDataTypeIndex::Returned, node_index, &poly_progress_section
         );
         if progress_subject_1 || progress_subject_2 { self.queue_node(subject_index); }
         if progress_field_1 || progress_field_2 { self.queue_node_parent(node_index); }
         poly_progress_section.forget();
         self.finish_polydata_constraint(node_index);
         return Ok(())
+    }
     fn progress_inference_rule_select_tuple_member(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let rule = node.inference_rule.as_select_tuple_member();
         let subject_index = rule.subject_index;
         let tuple_member_index = rule.selected_index;
         if node.field_index < 0 {
             let subject_type = &self.infer_nodes[subject_index].expr_type;
             let tuple_size = get_tuple_size_from_inference_type(subject_type);
             let tuple_size = match tuple_size {
                 Ok(Some(tuple_size)) => {
                     tuple_size
                 },
                 Ok(None) => {
                     // We can't infer anything yet
                     return Ok(())
                 },
                 Err(()) => {
                     let select_expr_span = ctx.heap[node.expr_id].full_span();
                     return Err(ParseError::new_error_at_span(
                         &ctx.module().source, select_expr_span, format!(
                             "tuple element select cannot be applied to a subject of type '{}'",
                             subject_type.display_name(&ctx.heap)
+                        )
                     ));
+                }
             };
             // If here then we at least have the tuple size. Now check if the
             // index doesn't exceed that size.
             if tuple_member_index >= tuple_size as u64 {
                 let select_expr_span = ctx.heap[node.expr_id].full_span();
                 return Err(ParseError::new_error_at_span(
                     &ctx.module().source, select_expr_span, format!(
                         "element index {} is out of bounds, tuple has {} elements",
                         tuple_member_index, tuple_size
+                    )
                 ));
+            }
             // Within bounds, set index on the type inference node
             let node = &mut self.infer_nodes[node_index];
             node.field_index = tuple_member_index as i32;
+        }
         // If here then we know we can use `tuple_member_index`. We need to keep
         // computing the offset to the subtype, as its value changes during
         // inference
         let subject_type = &self.infer_nodes[subject_index].expr_type;
         let mut selected_member_start_index = 1; // start just after the InferenceTypeElement::Tuple
         for _ in 0..tuple_member_index {
             selected_member_start_index = InferenceType::find_subtree_end_idx(&subject_type.parts, selected_member_start_index);
+        }
         let (progress_member, progress_subject) = self.apply_equal2_constraint(
             ctx, node_index, node_index, 0, subject_index, selected_member_start_index
         )?;
         if progress_member { self.queue_node_parent(node_index); }
         if progress_subject { self.queue_node(subject_index); }
         return Ok(());
+    }
     fn progress_inference_rule_literal_struct(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let node_expr_id = node.expr_id;
         let rule = node.inference_rule.as_literal_struct();
         // For each of the fields in the literal struct, apply the type equality
         // constraint. If the literal is polymorphic, then we try to progress
         // their types during this process
         let element_indices_section = self.index_buffer.start_section_initialized(&rule.element_indices);
         let mut poly_progress_section = self.poly_progress_buffer.start_section();
         for (field_index, field_node_index) in element_indices_section.iter_copied().enumerate() {
             let field_expr_id = self.infer_nodes[field_node_index].expr_id;
             let (_, progress_field) = self.apply_polydata_equal2_constraint(
                 ctx, node_index, field_expr_id, "struct field's",
                 PolyDataTypeIndex::Associated(field_index), 0,
                 field_node_index, 0, &mut poly_progress_section
             )?;
             if progress_field { self.queue_node(field_node_index); }
+        }
         // Now we do the same thing for the struct literal expression (the type
         // of the struct itself).
         let (_, progress_literal_1) = self.apply_polydata_equal2_constraint(
             ctx, node_index, node_expr_id, "struct literal's",
             PolyDataTypeIndex::Returned, 0, node_index, 0, &mut poly_progress_section
         )?;
         // And the other way around: if any of our polymorphic variables are
         // more specific then they were before, then we forward that information
         // back to our struct/fields.
         for (field_index, field_node_index) in element_indices_section.iter_copied().enumerate() {
             let progress_field = self.apply_polydata_polyvar_constraint(
                 ctx, node_index, PolyDataTypeIndex::Associated(field_index),
                 field_node_index, &poly_progress_section
             );
             if progress_field { self.queue_node(field_node_index); }
+        }
         let progress_literal_2 = self.apply_polydata_polyvar_constraint(
             ctx, node_index, PolyDataTypeIndex::Returned,
             node_index, &poly_progress_section
         );
         if progress_literal_1 || progress_literal_2 { self.queue_node_parent(node_index); }
         poly_progress_section.forget();
         element_indices_section.forget();
         self.finish_polydata_constraint(node_index);
         return Ok(())
+    }
     fn progress_inference_rule_literal_enum(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let node_expr_id = node.expr_id;
         let mut poly_progress_section = self.poly_progress_buffer.start_section();
         // An enum literal type is simply, well, the enum's type. However, it
         // might still have polymorphic variables, hence the use of `PolyData`.
         let (_, progress_literal_1) = self.apply_polydata_equal2_constraint(
             ctx, node_index, node_expr_id, "enum literal's",
             PolyDataTypeIndex::Returned, 0, node_index, 0, &mut poly_progress_section
         )?;
         let progress_literal_2 = self.apply_polydata_polyvar_constraint(
             ctx, node_index, PolyDataTypeIndex::Returned, node_index, &poly_progress_section
         );
         if progress_literal_1 || progress_literal_2 { self.queue_node_parent(node_index); }
         poly_progress_section.forget();
         self.finish_polydata_constraint(node_index);
         return Ok(());
+    }
     fn progress_inference_rule_literal_union(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let node_expr_id = node.expr_id;
         let rule = node.inference_rule.as_literal_union();
         // Infer type of any embedded values in the union variant. At the same
         // time progress the polymorphic variables associated with the union.
         let element_indices_section = self.index_buffer.start_section_initialized(&rule.element_indices);
         let mut poly_progress_section = self.poly_progress_buffer.start_section();
         for (embedded_index, embedded_node_index) in element_indices_section.iter_copied().enumerate() {
             let embedded_node_expr_id = self.infer_nodes[embedded_node_index].expr_id;
             let (_, progress_embedded) = self.apply_polydata_equal2_constraint(
                 ctx, node_index, embedded_node_expr_id, "embedded value's",
                 PolyDataTypeIndex::Associated(embedded_index), 0,
                 embedded_node_index, 0, &mut poly_progress_section
             )?;
             if progress_embedded { self.queue_node(embedded_node_index); }
+        }
         let (_, progress_literal_1) = self.apply_polydata_equal2_constraint(
             ctx, node_index, node_expr_id, "union's",
             PolyDataTypeIndex::Returned, 0, node_index, 0, &mut poly_progress_section
         )?;
         // Propagate progress in the polymorphic variables to the expressions
         // that constitute the union literal.
         for (embedded_index, embedded_node_index) in element_indices_section.iter_copied().enumerate() {
             let progress_embedded = self.apply_polydata_polyvar_constraint(
                 ctx, node_index, PolyDataTypeIndex::Associated(embedded_index),
                 embedded_node_index, &poly_progress_section
             );
             if progress_embedded { self.queue_node(embedded_node_index); }
+        }
         let progress_literal_2 = self.apply_polydata_polyvar_constraint(
             ctx, node_index, PolyDataTypeIndex::Returned, node_index, &poly_progress_section
         );
         if progress_literal_1 || progress_literal_2 { self.queue_node_parent(node_index); }
         poly_progress_section.forget();
         self.finish_polydata_constraint(node_index);
         return Ok(());
+    }
     fn progress_inference_rule_literal_array(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let rule = node.inference_rule.as_literal_array();
         // Apply equality rule to all of the elements that form the array
         let argument_node_indices = self.index_buffer.start_section_initialized(&rule.element_indices);
         let mut argument_progress_section = self.bool_buffer.start_section();
         self.apply_equal_n_constraint(ctx, node_index, &argument_node_indices, &mut argument_progress_section)?;
         debug_assert_eq!(argument_node_indices.len(), argument_progress_section.len());
         for argument_index in 0..argument_node_indices.len() {
             let argument_node_index = argument_node_indices[argument_index];
             let progress = argument_progress_section[argument_index];
             if progress { self.queue_node(argument_node_index); }
+        }
         // If elements are of type `T`, then the array is of type `Array<T>`, so:
         let mut progress_literal = self.apply_template_constraint(ctx, node_index, &ARRAY_TEMPLATE)?;
         if argument_node_indices.len() != 0 {
             let argument_node_index = argument_node_indices[0];
             let (progress_literal_inner, progress_argument) = self.apply_equal2_constraint(
                 ctx, node_index, node_index, 1, argument_node_index, 0
             )?;
             progress_literal = progress_literal || progress_literal_inner;
             // It is possible that the `Array<T>` has a more progress `T` then
             // the arguments. So in the case we progress our argument type we
             // simply queue this rule again
             if progress_argument { self.queue_node(node_index); }
+        }
         argument_node_indices.forget();
         argument_progress_section.forget();
         if progress_literal { self.queue_node_parent(node_index); }
         return Ok(());
+    }
     fn progress_inference_rule_literal_tuple(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let rule = node.inference_rule.as_literal_tuple();
         let element_indices = self.index_buffer.start_section_initialized(&rule.element_indices);
         // Check if we need to apply the initial tuple template type. Note that
         // this is a hacky check.
         let num_tuple_elements = rule.element_indices.len();
         let mut template_type = Vec::with_capacity(num_tuple_elements + 1); // TODO: @performance
         template_type.push(InferenceTypePart::Tuple(num_tuple_elements as u32));
         for _ in 0..num_tuple_elements {
             template_type.push(InferenceTypePart::Unknown);
+        }
         let mut progress_literal = self.apply_template_constraint(ctx, node_index, &template_type)?;
         // Because of the (early returning error) check above, we're certain
         // that the tuple has the correct number of elements. Now match each
         // element expression type to the tuple subtype.
         let mut element_subtree_start_index = 1; // first element is InferenceTypePart::Tuple
         for element_node_index in element_indices.iter_copied() {
             let (progress_literal_element, progress_element) = self.apply_equal2_constraint(
                 ctx, node_index, node_index, element_subtree_start_index, element_node_index, 0
             )?;
             progress_literal = progress_literal || progress_literal_element;
             if progress_element {
                 self.queue_node(element_node_index);
+            }
             // Prepare for next element
             let node = &self.infer_nodes[node_index];
             let subtree_end_index = InferenceType::find_subtree_end_idx(&node.expr_type.parts, element_subtree_start_index);
             element_subtree_start_index = subtree_end_index;
+        }
         debug_assert_eq!(element_subtree_start_index, self.infer_nodes[node_index].expr_type.parts.len());
         if progress_literal { self.queue_node_parent(node_index); }
         element_indices.forget();
         return Ok(());
+    }
     fn progress_inference_rule_cast_expr(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let rule = node.inference_rule.as_cast_expr();
         let subject_index = rule.subject_index;
         let subject = &self.infer_nodes[subject_index];
         // Make sure that both types are completely done. Note: a cast
         // expression cannot really infer anything between the subject and the
         // output type, we can only make sure that, at the end, the cast is
         // correct.
         if !node.expr_type.is_done || !subject.expr_type.is_done {
             return Ok(());
+        }
         // Both types are known, currently the only valid casts are bool,
         // integer and character casts.
         fn is_bool_int_or_char(parts: &[InferenceTypePart]) -> bool {
             let mut index = 0;
             while index < parts.len() {
                 let part = &parts[index];
                 if !part.is_marker() { break; }
                 index += 1;
+            }
             debug_assert!(index != parts.len());
             let part = &parts[index];
             if *part == InferenceTypePart::Bool || *part == InferenceTypePart::Character || part.is_concrete_integer() {
                 debug_assert!(index + 1 == parts.len()); // type is done, first part does not have children -> must be at end
                 return true;
             } else {
                 return false;
+            }
+        }
         let is_valid = if is_bool_int_or_char(&node.expr_type.parts) && is_bool_int_or_char(&subject.expr_type.parts) {
             true
         } else if InferenceType::check_subtrees(&node.expr_type.parts, 0, &subject.expr_type.parts, 0) {
             // again: check_subtrees is sufficient since both types are done
             true
         } else {
             false
         };
         if !is_valid {
             let cast_expr = &ctx.heap[node.expr_id];
             let subject_expr = &ctx.heap[subject.expr_id];
             return Err(ParseError::new_error_str_at_span(
                 &ctx.module().source, cast_expr.full_span(), "invalid casting operation"
             ).with_info_at_span(
                 &ctx.module().source, subject_expr.full_span(), format!(
                     "cannot cast the argument type '{}' to the type '{}'",
                     subject.expr_type.display_name(&ctx.heap),
                     node.expr_type.display_name(&ctx.heap)
+                )
             ));
+        }
         return Ok(())
+    }
     fn progress_inference_rule_call_expr(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &self.infer_nodes[node_index];
         let node_expr_id = node.expr_id;
         let rule = node.inference_rule.as_call_expr();
         let mut poly_progress_section = self.poly_progress_buffer.start_section();
         let argument_node_indices = self.index_buffer.start_section_initialized(&rule.argument_indices);
         // Perform inference on arguments to function, while trying to figure
         // out the polymorphic variables
         for (argument_index, argument_node_index) in argument_node_indices.iter_copied().enumerate() {
             let argument_expr_id = self.infer_nodes[argument_node_index].expr_id;
             let (_, progress_argument) = self.apply_polydata_equal2_constraint(
                 ctx, node_index, argument_expr_id, "argument's",
                 PolyDataTypeIndex::Associated(argument_index), 0,
                 argument_node_index, 0, &mut poly_progress_section
             )?;
             if progress_argument { self.queue_node(argument_node_index); }
+        }
         // Same for the return type.
         let (_, progress_call_1) = self.apply_polydata_equal2_constraint(
             ctx, node_index, node_expr_id, "return",
             PolyDataTypeIndex::Returned, 0,
             node_index, 0, &mut poly_progress_section
         )?;
         // We will now apply any progression in the polymorphic variable type
         // back to the arguments.
         for (argument_index, argument_node_index) in argument_node_indices.iter_copied().enumerate() {
             let progress_argument = self.apply_polydata_polyvar_constraint(
                 ctx, node_index, PolyDataTypeIndex::Associated(argument_index),
                 argument_node_index, &poly_progress_section
             );
             if progress_argument { self.queue_node(argument_node_index); }
+        }
         // And back to the return type.
         let progress_call_2 = self.apply_polydata_polyvar_constraint(
             ctx, node_index, PolyDataTypeIndex::Returned,
             node_index, &poly_progress_section
         );
         if progress_call_1 || progress_call_2 { self.queue_node_parent(node_index); }
         poly_progress_section.forget();
         argument_node_indices.forget();
         self.finish_polydata_constraint(node_index);
         return Ok(())
+    }
     fn progress_inference_rule_variable_expr(&mut self, ctx: &Ctx, node_index: InferNodeIndex) -> Result<(), ParseError> {
         let node = &mut self.infer_nodes[node_index];
         let rule = node.inference_rule.as_variable_expr();
         let var_data_index = rule.var_data_index;
         let var_data = &mut self.var_data[var_data_index];
         // Apply inference to the shared variable type and the expression type
         let shared_type: *mut _ = &mut var_data.var_type;
         let expr_type: *mut _ = &mut node.expr_type;
         let inference_result = unsafe {
             // safety: vectors exist in different storage vectors, so cannot alias
             InferenceType::infer_subtrees_for_both_types(shared_type, 0, expr_type, 0)
         };
         if inference_result == DualInferenceResult::Incompatible {
             return Err(self.construct_variable_type_error(ctx, node_index));
+        }
         let progress_var_data = inference_result.modified_lhs();
         let progress_expr = inference_result.modified_rhs();
         if progress_var_data {
             // We progressed the type of the shared variable, so propagate this
             // to all associated variable expressions (and relatived variables).
             for other_node_index in var_data.used_at.iter().copied() {
                 if other_node_index != node_index {
                     self.node_queued.push_back(other_node_index);
+                }
+            }
             if let Some(linked_var_data_index) = var_data.linked_var {
                 // Only perform one-way inference, progressing the linked
                 // variable.
                 // note: because this "linking" is used only for channels, we
                 // will start inference one level below the top-level in the
                 // type tree (i.e. ensure `T` in `in<T>` and `out<T>` is equal).
                 debug_assert!(
                     var_data.var_type.parts[0] == InferenceTypePart::Input ||
                     var_data.var_type.parts[0] == InferenceTypePart::Output
                 );
                 let this_var_type: *const _ = &var_data.var_type;
                 let linked_var_data = &mut self.var_data[linked_var_data_index];
                 debug_assert!(
                     linked_var_data.var_type.parts[0] == InferenceTypePart::Input ||
                     linked_var_data.var_type.parts[0] == InferenceTypePart::Output
                 );
                 // safety: by construction var_data_index and linked_var_data_index cannot be the
                 // same, hence we're not aliasing here.
                 let inference_result = InferenceType::infer_subtree_for_single_type(
                     &mut linked_var_data.var_type, 1,
                     unsafe{ &(*this_var_type).parts }, 1, false
                 );
                 match inference_result {
                     SingleInferenceResult::Modified => {
                         for used_at in linked_var_data.used_at.iter().copied() {
                             self.node_queued.push_back(used_at);
+                        }
                     },
                     SingleInferenceResult::Unmodified => {},
                     SingleInferenceResult::Incompatible => {
                         let var_data_this = &self.var_data[var_data_index];
                         let var_decl_this = &ctx.heap[var_data_this.var_id];
                         let var_data_linked = &self.var_data[linked_var_data_index];
                         let var_decl_linked = &ctx.heap[var_data_linked.var_id];
                         return Err(ParseError::new_error_at_span(
                             &ctx.module().source, var_decl_this.identifier.span, format!(
                                 "conflicting types for this channel, this port has type '{}'",
                                 var_data_this.var_type.display_name(&ctx.heap)
+                            )
                         ).with_info_at_span(
                             &ctx.module().source, var_decl_linked.identifier.span, format!(
                                 "while this port has type '{}'",
                                 var_data_linked.var_type.display_name(&ctx.heap)
+                            )
                         ));
+                    }
+                }
+            }
+        }
         if progress_expr { self.queue_node_parent(node_index); }
         return Ok(());
+    }
     fn progress_template(&mut self, ctx: &Ctx, node_index: InferNodeIndex, application: InferenceRuleTemplateApplication, template: &[InferenceTypePart]) -> Result<bool, ParseError> {
         use InferenceRuleTemplateApplication as TA;
         match application {
             TA::None => Ok(false),
             TA::Template => self.apply_template_constraint(ctx, node_index, template),
             TA::Forced => self.apply_forced_constraint(ctx, node_index, template),
+        }
+    }
     fn queue_node_parent(&mut self, node_index: InferNodeIndex) {
         let node = &self.infer_nodes[node_index];
         if let Some(parent_node_index) = node.parent_index {
             self.node_queued.push_back(parent_node_index);
+        }
+    }
     #[inline]
     fn queue_node(&mut self, node_index: InferNodeIndex) {
         self.node_queued.push_back(node_index);
+    }
     /// Returns whether the type is certainly a string (true, false), certainly
     /// not a string (false, true), or still unknown (false, false).
     fn type_is_certainly_or_certainly_not_string(&self, node_index: InferNodeIndex) -> (bool, bool) {
         let expr_type = &self.infer_nodes[node_index].expr_type;
         let mut part_index = 0;
         while part_index < expr_type.parts.len() {
             let part = &expr_type.parts[part_index];
             if part.is_marker() {
                 part_index += 1;
                 continue;
+            }
             if !part.is_concrete() { break; }
             if *part == InferenceTypePart::String {
                 // First part is a string
                 return (true, false);
             } else {
                 return (false, true);
+            }
+        }
         // If here then first non-marker type is not concrete
         if part_index == expr_type.parts.len() {
             // nothing known at all
             return (false, false);
+        }
         // Special case: array-like where its argument is not a character
         if part_index + 1 < expr_type.parts.len() {
             if expr_type.parts[part_index] == InferenceTypePart::ArrayLike && expr_type.parts[part_index + 1] != InferenceTypePart::Character {
                 return (false, true);
+            }
+        }
         (false, false)
+    }
     /// Applies a template type constraint: the type associated with the
     /// supplied expression will be molded into the provided `template`. But
     /// will be considered valid if the template could've been molded into the
     /// expression type as well. Hence the template may be fully specified (e.g.
     /// a bool) or contain "inference" variables (e.g. an array of T)
     fn apply_template_constraint(
         &mut self, ctx: &Ctx, node_index: InferNodeIndex, template: &[InferenceTypePart]
     ) -> Result<bool, ParseError> {
         let expr_type = &mut self.infer_nodes[node_index].expr_type;
         match InferenceType::infer_subtree_for_single_type(expr_type, 0, template, 0, false) {
             SingleInferenceResult::Modified => Ok(true),
             SingleInferenceResult::Unmodified => Ok(false),
             SingleInferenceResult::Incompatible => Err(
                 self.construct_template_type_error(ctx, node_index, template)
+            )
+        }
+    }
     /// Applies a forced constraint: the supplied expression's type MUST be
     /// inferred from the template, the other way around is considered invalid.
     fn apply_forced_constraint(
         &mut self, ctx: &Ctx, node_index: InferNodeIndex, template: &[InferenceTypePart]
     ) -> Result<bool, ParseError> {
         let expr_type = &mut self.infer_nodes[node_index].expr_type;
         match InferenceType::infer_subtree_for_single_type(expr_type, 0, template, 0, true) {
             SingleInferenceResult::Modified => Ok(true),
             SingleInferenceResult::Unmodified => Ok(false),
             SingleInferenceResult::Incompatible => Err(
                 self.construct_template_type_error(ctx, node_index, template)
+            )
+        }
+    }
     /// Applies a type constraint that expects the two provided types to be
     /// equal. We attempt to make progress in inferring the types. If the call
     /// is successful then the composition of all types are made equal.
     /// The "parent" `expr_id` is provided to construct errors.
     fn apply_equal2_constraint(
         &mut self, ctx: &Ctx, node_index: InferNodeIndex,
         arg1_index: InferNodeIndex, arg1_start_idx: usize,
         arg2_index: InferNodeIndex, arg2_start_idx: usize
     ) -> Result<(bool, bool), ParseError> {
         let arg1_type: *mut _ = &mut self.infer_nodes[arg1_index].expr_type;
         let arg2_type: *mut _ = &mut self.infer_nodes[arg2_index].expr_type;
         let infer_res = unsafe{ InferenceType::infer_subtrees_for_both_types(
             arg1_type, arg1_start_idx,
             arg2_type, arg2_start_idx
         ) };
         if infer_res == DualInferenceResult::Incompatible {
             return Err(self.construct_arg_type_error(ctx, node_index, arg1_index, arg2_index));
+        }
         Ok((infer_res.modified_lhs(), infer_res.modified_rhs()))
+    }
     /// Applies an equal2 constraint between a member of the `PolyData` struct,
     /// and another inferred type. If any progress is made in the `PolyData`
     /// struct then the affected polymorphic variables are updated as well.
     ///
     /// Because a lot of types/expressions are involved in polymorphic typFe
     /// inference, some explanation: "outer_node" refers to the main expression
     /// that is the root cause of type inference (e.g. a struct literal
     /// expression, or a tuple member select expression). Associated with that
     /// outer node is `PolyData`, so that is what the "poly_data" variables
     /// are referring to. We are applying equality between a "poly_data" type
     /// and an associated expression (not necessarily the "outer_node", e.g.
     /// the expression that constructs the value of a struct field). Hence the
     /// "associated" variables.
     ///
     /// Finally, when an error occurs we'll first show the outer node's
     /// location. As info, the `error_location_expr_id` span is shown,
     /// indicating that the "`error_type_name` type has been resolved to
     /// `outer_node_type`, but this expression has been resolved to
     /// `associated_node_type`".
     fn apply_polydata_equal2_constraint(
         &mut self, ctx: &Ctx,
         outer_node_index: InferNodeIndex, error_location_expr_id: ExpressionId, error_type_name: &str,
         poly_data_type_index: PolyDataTypeIndex, poly_data_start_index: usize,
         associated_node_index: InferNodeIndex, associated_node_start_index: usize,
         poly_progress_section: &mut ScopedSection<u32>,
     ) -> Result<(bool, bool), ParseError> {
         let poly_data_index = self.infer_nodes[outer_node_index].poly_data_index;
         let poly_data = &mut self.poly_data[poly_data_index as usize];
         let poly_data_type = poly_data.expr_types.get_type_mut(poly_data_type_index);
         let associated_type: *mut _ = &mut self.infer_nodes[associated_node_index].expr_type;
         let inference_result = unsafe{
             // Safety: pointers originate from different vectors, so cannot
             // alias.
             let poly_data_type: *mut _ = poly_data_type;
             InferenceType::infer_subtrees_for_both_types(
                 poly_data_type, poly_data_start_index,
                 associated_type, associated_node_start_index
+            )
         };
         let modified_poly_data = inference_result.modified_lhs();
         let modified_associated = inference_result.modified_rhs();
         if inference_result == DualInferenceResult::Incompatible {
             let outer_node_expr_id = self.infer_nodes[outer_node_index].expr_id;
             let outer_node_span = ctx.heap[outer_node_expr_id].full_span();
             let detailed_span = ctx.heap[error_location_expr_id].full_span();
             let outer_node_type = poly_data_type.display_name(&ctx.heap);
             let associated_type = self.infer_nodes[associated_node_index].expr_type.display_name(&ctx.heap);
             let source = &ctx.module().source;
             return Err(ParseError::new_error_str_at_span(
                 source, outer_node_span, "failed to resolve the types of this expression"
             ).with_info_str_at_span(
                 source, detailed_span, &format!(
                     "because the {} type has been resolved to '{}', but this expression has been resolved to '{}'",
                     error_type_name, outer_node_type, associated_type
+                )
             ));
+        }
         if modified_poly_data {
             debug_assert!(poly_data_type.has_marker);
             // Go through markers for polymorphic variables and use the
             // (hopefully) more specific types to update their representation
             // in the PolyData struct
             for (poly_var_index, poly_var_section) in poly_data_type.marker_iter() {
                 let poly_var_type = &mut poly_data.poly_vars[poly_var_index as usize];
                 match InferenceType::infer_subtree_for_single_type(poly_var_type, 0, poly_var_section, 0, false) {
                     SingleInferenceResult::Modified => {
                         poly_progress_section.push_unique(poly_var_index);
                     },
                     SingleInferenceResult::Unmodified => {
                         // nothing to do
                     },
                     SingleInferenceResult::Incompatible => {
                         return Err(Self::construct_poly_arg_error(
                             ctx, &self.poly_data[poly_data_index as usize],
                             self.infer_nodes[outer_node_index].expr_id
                         ));
+                    }
+                }
+            }
+        }
         return Ok((modified_poly_data, modified_associated));
+    }
     /// After calling `apply_polydata_equal2_constraint` on several expressions
     /// that are associated with some kind of polymorphic expression, several of
     /// the polymorphic variables might have been inferred to more specific
     /// types than before.
     ///
     /// At this point one should call this function to apply the progress in
     /// these polymorphic variables back onto the types that are functions of
     /// these polymorphic variables.
     ///
     /// An example: a struct literal with a polymorphic variable `T` may have
     /// two fields `foo` and `bar` each with different types that are a function
     /// of the polymorhic variable `T`. If the expressions constructing the
     /// value for the field `foo` causes the type `T` to progress, then we can
     /// also progress the type of the expression that constructs `bar`.
     ///
     /// And so we have `outer_node_index` + `poly_data_type_index` pointing to
     /// the appropriate type in the `PolyData` struct. Which will be updated
     /// first using the polymorphic variables. If we happen to have updated that
     /// type, then we should also progress the associated expression, hence the
     /// `associated_node_index`.
     fn apply_polydata_polyvar_constraint(
         &mut self, _ctx: &Ctx,
         outer_node_index: InferNodeIndex, poly_data_type_index: PolyDataTypeIndex,
         associated_node_index: InferNodeIndex, poly_progress_section: &ScopedSection<u32>
     ) -> bool {
         let poly_data_index = self.infer_nodes[outer_node_index].poly_data_index;
         let poly_data = &mut self.poly_data[poly_data_index as usize];
         // Early exit, most common case (literals or functions calls which are
         // actually not polymorphic)
         if !poly_data.first_rule_application && poly_progress_section.len() == 0 {
             return false;
+        }
         // safety: we're borrowing from two distinct fields, so should be fine
         let poly_data_type = poly_data.expr_types.get_type_mut(poly_data_type_index);
         let mut last_start_index = 0;
         let mut modified_poly_type = false;
         while let Some((poly_var_index, poly_var_start_index)) = poly_data_type.find_marker(last_start_index) {
             let poly_var_end_index = InferenceType::find_subtree_end_idx(&poly_data_type.parts, poly_var_start_index);
             if poly_data.first_rule_application || poly_progress_section.contains(&poly_var_index) {
                 // We have updated this polymorphic variable, so try updating it
                 // in the PolyData type
                 let modified_in_poly_data = match InferenceType::infer_subtree_for_single_type(
                     poly_data_type, poly_var_start_index, &poly_data.poly_vars[poly_var_index as usize].parts, 0, false
                 ) {
                     SingleInferenceResult::Modified => true,
                     SingleInferenceResult::Unmodified => false,
                     SingleInferenceResult::Incompatible => {
                         // practically impossible: before calling this function we gather all the
                         // data on the polymorphic variables from the associated expressions. So if
                         // the polymorphic variables in those expressions were not mutually
                         // compatible, we must have encountered that error already.
                         unreachable!()
                     },
                 };
                 modified_poly_type = modified_poly_type || modified_in_poly_data;
+            }
             last_start_index = poly_var_end_index;
+        }
         if modified_poly_type {
             let associated_type = &mut self.infer_nodes[associated_node_index].expr_type;
             match InferenceType::infer_subtree_for_single_type(
                 associated_type, 0, &poly_data_type.parts, 0, true
             ) {
                 SingleInferenceResult::Modified => return true,
                 SingleInferenceResult::Unmodified => return false,
                 SingleInferenceResult::Incompatible => unreachable!(), // same as above
+            }
         } else {
             // Did not update associated type
             return false;
+        }
+    }
     /// Should be called after completing one full round of applying polydata
     /// constraints.
     fn finish_polydata_constraint(&mut self, outer_node_index: InferNodeIndex) {
         let poly_data_index = self.infer_nodes[outer_node_index].poly_data_index;
         let poly_data = &mut self.poly_data[poly_data_index as usize];
         poly_data.first_rule_application = false;
+    }
     /// Applies a type constraint that expects all three provided types to be
     /// equal. In case we can make progress in inferring the types then we
     /// attempt to do so. If the call is successful then the composition of all
     /// types is made equal.
     fn apply_equal3_constraint(
         &mut self, ctx: &Ctx, node_index: InferNodeIndex,
         arg1_index: InferNodeIndex, arg2_index: InferNodeIndex,
         start_idx: usize
     ) -> Result<(bool, bool, bool), ParseError> {
         // Safety: all indices are unique
         //         containers may not be modified
         let expr_type: *mut _ = &mut self.infer_nodes[node_index].expr_type;
         let arg1_type: *mut _ = &mut self.infer_nodes[arg1_index].expr_type;
         let arg2_type: *mut _ = &mut self.infer_nodes[arg2_index].expr_type;
         let expr_res = unsafe{
             InferenceType::infer_subtrees_for_both_types(expr_type, start_idx, arg1_type, start_idx)
         };
         if expr_res == DualInferenceResult::Incompatible {
             return Err(self.construct_expr_type_error(ctx, node_index, arg1_index));
+        }
         let args_res = unsafe{
             InferenceType::infer_subtrees_for_both_types(arg1_type, start_idx, arg2_type, start_idx) };
         if args_res == DualInferenceResult::Incompatible {
             return Err(self.construct_arg_type_error(ctx, node_index, arg1_index, arg2_index));
+        }
         // If all types are compatible, but the second call caused the arg1_type
         // to be expanded, then we must also assign this to expr_type.
         let mut progress_expr = expr_res.modified_lhs();
         let mut progress_arg1 = expr_res.modified_rhs();
         let progress_arg2 = args_res.modified_rhs();
         if args_res.modified_lhs() {
             unsafe {
                 let end_idx = InferenceType::find_subtree_end_idx(&(*arg2_type).parts, start_idx);
                 let subtree = &((*arg2_type).parts[start_idx..end_idx]);
                 (*expr_type).replace_subtree(start_idx, subtree);
+            }
             progress_expr = true;
             progress_arg1 = true;
+        }
         Ok((progress_expr, progress_arg1, progress_arg2))
+    }
     /// Applies equal constraint to N consecutive expressions. The returned
     /// `progress` vec will contain which expressions were progressed and will
     /// have length N.
     fn apply_equal_n_constraint(
         &mut self, ctx: &Ctx, outer_node_index: InferNodeIndex,
         arguments: &ScopedSection<InferNodeIndex>, progress: &mut ScopedSection<bool>
     ) -> Result<(), ParseError> {
         // Depending on the argument perform an early exit. This simplifies
         // later logic
         debug_assert_eq!(progress.len(), 0);
         match arguments.len() {
 => {
                 // nothing to progress
                 return Ok(())
             },
 => {
                 // only one type, so nothing to infer
                 progress.push(false);
                 return Ok(())
             },
             n => {
                 for _ in 0..n {
                     progress.push(false);
+                }
+            }
+        }
         // We'll start doing pairwise inference for all of the inference nodes
         // (node[0] with node[1], then node[1] with node[2], then node[2] ...,
         // etc.), so when we're at the end we have `node[N-1]` as the most
         // progressed type.
         let mut last_index_requiring_inference = 0;
         for prev_argument_index in 0..arguments.len() - 1 {
             let next_argument_index = prev_argument_index + 1;
             let prev_node_index = arguments[prev_argument_index];
             let next_node_index = arguments[next_argument_index];
             let (prev_progress, next_progress) = self.apply_equal2_constraint(
                 ctx, outer_node_index, prev_node_index, 0, next_node_index, 0
             )?;
             if prev_progress {
                 // Previous node is progress, so every type in front of it needs
                 // to be reinferred.
                 progress[prev_argument_index] = true;
                 last_index_requiring_inference = prev_argument_index;
+            }
             progress[next_argument_index] = next_progress;
+        }
         // Apply inference using the most progressed type (the last one) to the
         // ones that did not obtain this information during the inference
         // process.
         let last_argument_node_index = arguments[arguments.len() - 1];
         let last_argument_type: *mut _ = &mut self.infer_nodes[last_argument_node_index].expr_type;
         for argument_index in 0..last_index_requiring_inference {
             // We can cheat, we know the LHS is less specific than the right
             // hand side, so:
             let argument_node_index = arguments[argument_index];
             let argument_type = &mut self.infer_nodes[argument_node_index].expr_type;
             unsafe {
                 // safety: we're dealing with different vectors, so cannot alias
                 argument_type.replace_subtree(0, &(*last_argument_type).parts);
+            }
             progress[argument_index] = true;
+        }
         return Ok(());
+    }
     /// Determines the `InferenceType` for the expression based on the
     /// expression parent (this is not done if the parent is a regular 'ol
     /// expression). Expects `parent_index` to be set to the parent of the
     /// inference node that is created here.
     fn insert_initial_inference_node(
         &mut self, ctx: &mut Ctx, expr_id: ExpressionId
     ) -> Result<InferNodeIndex, ParseError> {
         use ExpressionParent as EP;
         use InferenceTypePart as ITP;
         // Set the initial inference type based on the expression parent.
         let expr = &ctx.heap[expr_id];
         let inference_type = match expr.parent() {
             EP::None =>
                 // Should have been set by linker
                 unreachable!(),
             EP::Memory(_) | EP::ExpressionStmt(_) =>
                 // Determined during type inference
                 InferenceType::new(false, false, vec![ITP::Unknown]),
             EP::Expression(parent_id, idx_in_parent) => {
                 // If we are the test expression of a conditional expression,
                 // then we must resolve to a boolean
                 let is_conditional = if let Expression::Conditional(_) = &ctx.heap[*parent_id] {
                     true
                 } else {
                     false
                 };
                 if is_conditional && *idx_in_parent == 0 {
                     InferenceType::new(false, true, vec![ITP::Bool])
                 } else {
                     InferenceType::new(false, false, vec![ITP::Unknown])
+                }
             },
             EP::If(_) | EP::While(_) =>
                 // Must be a boolean
                 InferenceType::new(false, true, vec![ITP::Bool]),
             EP::Return(_) => {
                 // Must match the return type of the function
                 debug_assert_eq!(self.procedure_kind, ProcedureKind::Function);
                 let returned = &ctx.heap[self.procedure_id].return_type.as_ref().unwrap();
                 self.determine_inference_type_from_parser_type_elements(&returned.elements, true)
             },
             EP::New(_) =>
                 // Must be a component call, which we assign a "Void" return
                 // type
                 InferenceType::new(false, true, vec![ITP::Void]),
         };
         let infer_index = self.infer_nodes.len() as InferNodeIndex;
         self.infer_nodes.push(InferenceNode {
             expr_type: inference_type,
             expr_id,
             inference_rule: InferenceRule::Noop,
             parent_index: self.parent_index,
             field_index: -1,
             poly_data_index: -1,
             info_type_id: TypeId::new_invalid(),
             info_variant: ExpressionInfoVariant::Generic,
         });
         return Ok(infer_index);
+    }
     fn insert_initial_call_polymorph_data(
         &mut self, ctx: &mut Ctx, call_id: CallExpressionId
     ) -> PolyDataIndex {
         // Note: the polymorph variables may be partially specified and may
         // contain references to the wrapping definition's (i.e. the proctype
         // we are currently visiting) polymorphic arguments.
         //
         // The arguments of the call may refer to polymorphic variables in the
         // definition of the function we're calling, not of the wrapping
         // definition. We insert markers in these inferred types to be able to
         // map them back and forth to the polymorphic arguments of the function
         // we are calling.
         let call = &ctx.heap[call_id];
         // Handle the polymorphic arguments (if there are any)
         let num_poly_args = call.parser_type.elements[0].variant.num_embedded();
         let mut poly_args = Vec::with_capacity(num_poly_args);
         for embedded_elements in call.parser_type.iter_embedded(0) {
             poly_args.push(self.determine_inference_type_from_parser_type_elements(embedded_elements, true));
+        }
         // Handle the arguments and return types
         let definition = &ctx.heap[call.procedure];
         debug_assert_eq!(poly_args.len(), definition.poly_vars.len());
         let mut parameter_types = Vec::with_capacity(definition.parameters.len());
         let parameter_section = self.var_buffer.start_section_initialized(&definition.parameters);
         for parameter_id in parameter_section.iter_copied() {
             let param = &ctx.heap[parameter_id];
             parameter_types.push(self.determine_inference_type_from_parser_type_elements(&param.parser_type.elements, false));
+        }
         parameter_section.forget();
         let return_type = match &definition.return_type {
             None => {
                 // Component, so returns a "Void"
                 debug_assert_ne!(definition.kind, ProcedureKind::Function);
                 InferenceType::new(false, true, vec![InferenceTypePart::Void])
             },
             Some(returned) => {
                 debug_assert_eq!(definition.kind, ProcedureKind::Function);
                 self.determine_inference_type_from_parser_type_elements(&returned.elements, false)
+            }
         };
         let extra_data_idx = self.poly_data.len() as PolyDataIndex;
         self.poly_data.push(PolyData {
             first_rule_application: true,
             definition_id: call.procedure.upcast(),
             poly_vars: poly_args,
             expr_types: PolyDataTypes {
                 associated: parameter_types,
                 returned: return_type
+            }
         });
         return extra_data_idx
+    }
     fn insert_initial_struct_polymorph_data(
         &mut self, ctx: &mut Ctx, lit_id: LiteralExpressionId,
     ) -> PolyDataIndex {
         use InferenceTypePart as ITP;
         let literal = ctx.heap[lit_id].value.as_struct();
         // Handle polymorphic arguments
         let num_embedded = literal.parser_type.elements[0].variant.num_embedded();
         let mut total_num_poly_parts = 0;
         let mut poly_args = Vec::with_capacity(num_embedded);
         for embedded_elements in literal.parser_type.iter_embedded(0) {
             let poly_type = self.determine_inference_type_from_parser_type_elements(embedded_elements, true);
             total_num_poly_parts += poly_type.parts.len();
             poly_args.push(poly_type);
+        }
         // Handle parser types on struct definition
         let defined_type = ctx.types.get_base_definition(&literal.definition).unwrap();
         let struct_type = defined_type.definition.as_struct();
         debug_assert_eq!(poly_args.len(), defined_type.poly_vars.len());
         // Note: programmer is capable of specifying fields in a struct literal
         // in a different order than on the definition. We take the literal-
         // specified order to be leading.
         let mut embedded_types = Vec::with_capacity(struct_type.fields.len());
         for lit_field in literal.fields.iter() {
             let def_field = &struct_type.fields[lit_field.field_idx];
             let inference_type = self.determine_inference_type_from_parser_type_elements(&def_field.parser_type.elements, false);
             embedded_types.push(inference_type);
+        }
         // Return type is the struct type itself, with the appropriate
         // polymorphic variables. So:
         // - 1 part for definition
         // - N_poly_arg marker parts for each polymorphic argument
         // - all the parts for the currently known polymorphic arguments
         let parts_reserved = 1 + poly_args.len() + total_num_poly_parts;
         let mut parts = Vec::with_capacity(parts_reserved);
         parts.push(ITP::Instance(literal.definition, poly_args.len() as u32));
         let mut return_type_done = true;
         for (poly_var_idx, poly_var) in poly_args.iter().enumerate() {
             if !poly_var.is_done { return_type_done = false; }
             parts.push(ITP::Marker(poly_var_idx as u32));
             parts.extend(poly_var.parts.iter().cloned());
+        }
         debug_assert_eq!(parts.len(), parts_reserved);
         let return_type = InferenceType::new(!poly_args.is_empty(), return_type_done, parts);
         let extra_data_index = self.poly_data.len() as PolyDataIndex;
         self.poly_data.push(PolyData {
             first_rule_application: true,
             definition_id: literal.definition,
             poly_vars: poly_args,
             expr_types: PolyDataTypes {
                 associated: embedded_types,
                 returned: return_type,
             },
         });
         return extra_data_index
+    }
     /// Inserts the extra polymorphic data struct for enum expressions. These
     /// can never be determined from the enum itself, but may be inferred from
     /// the use of the enum.
     fn insert_initial_enum_polymorph_data(
         &mut self, ctx: &Ctx, lit_id: LiteralExpressionId
     ) -> PolyDataIndex {
         use InferenceTypePart as ITP;
         let literal = ctx.heap[lit_id].value.as_enum();
         // Handle polymorphic arguments to the enum
         let num_poly_args = literal.parser_type.elements[0].variant.num_embedded();
         let mut total_num_poly_parts = 0;
         let mut poly_args = Vec::with_capacity(num_poly_args);
         for embedded_elements in literal.parser_type.iter_embedded(0) {
             let poly_type = self.determine_inference_type_from_parser_type_elements(embedded_elements, true);
             total_num_poly_parts += poly_type.parts.len();
             poly_args.push(poly_type);
+        }
         // Handle enum type itself
         let parts_reserved = 1 + poly_args.len() + total_num_poly_parts;
         let mut parts = Vec::with_capacity(parts_reserved);
         parts.push(ITP::Instance(literal.definition, poly_args.len() as u32));
         let mut enum_type_done = true;
         for (poly_var_idx, poly_var) in poly_args.iter().enumerate() {
             if !poly_var.is_done { enum_type_done = false; }
             parts.push(ITP::Marker(poly_var_idx as u32));
             parts.extend(poly_var.parts.iter().cloned());
+        }
         debug_assert_eq!(parts.len(), parts_reserved);
         let enum_type = InferenceType::new(!poly_args.is_empty(), enum_type_done, parts);
         let extra_data_index = self.poly_data.len() as PolyDataIndex;
         self.poly_data.push(PolyData {
             first_rule_application: true,
             definition_id: literal.definition,
             poly_vars: poly_args,
             expr_types: PolyDataTypes {
                 associated: Vec::new(),
                 returned: enum_type,
             },
         });
         return extra_data_index;
+    }
     /// Inserts the extra polymorphic data struct for unions. The polymorphic
     /// arguments may be partially determined from embedded values in the union.
     fn insert_initial_union_polymorph_data(
         &mut self, ctx: &Ctx, lit_id: LiteralExpressionId
     ) -> PolyDataIndex {
         use InferenceTypePart as ITP;
         let literal = ctx.heap[lit_id].value.as_union();
         // Construct the polymorphic variables
         let num_poly_args = literal.parser_type.elements[0].variant.num_embedded();
         let mut total_num_poly_parts = 0;
         let mut poly_args = Vec::with_capacity(num_poly_args);
         for embedded_elements in literal.parser_type.iter_embedded(0) {
             let poly_type = self.determine_inference_type_from_parser_type_elements(embedded_elements, true);
             total_num_poly_parts += poly_type.parts.len();
             poly_args.push(poly_type);
+        }
         // Handle any of the embedded values in the variant, if specified
         let definition_id = literal.definition;
         let type_definition = ctx.types.get_base_definition(&definition_id).unwrap();
         let union_definition = type_definition.definition.as_union();
         debug_assert_eq!(poly_args.len(), type_definition.poly_vars.len());
         let variant_definition = &union_definition.variants[literal.variant_idx];
         debug_assert_eq!(variant_definition.embedded.len(), literal.values.len());
         let mut embedded = Vec::with_capacity(variant_definition.embedded.len());
         for embedded_parser_type in &variant_definition.embedded {
             let inference_type = self.determine_inference_type_from_parser_type_elements(&embedded_parser_type.elements, false);
             embedded.push(inference_type);
+        }
         // Handle the type of the union itself

src/protocol/parser/type_table.rs

➞

Show inline comments

 /**
  * type_table.rs
+ *
  * The type table is a lookup from AST definition (which contains just what the
  * programmer typed) to a type with additional information computed (e.g. the
  * byte size and offsets of struct members). The type table should be considered
  * the authoritative source of information on types by the compiler (not the
  * AST itself!).
+ *
  * The type table operates in two modes: one is where we just look up the type,
  * check its fields for correctness and mark whether it is polymorphic or not.
  * The second one is where we compute byte sizes, alignment and offsets.
+ *
  * The basic algorithm for type resolving and computing byte sizes is to
  * recursively try to lay out each member type of a particular type. This is
  * done in a stack-like fashion, where each embedded type pushes a breadcrumb
  * unto the stack. We may discover a cycle in embedded types (we call this a
  * "type loop"). After which the type table attempts to break the type loop by
  * making specific types heap-allocated. Upon doing so we know their size
  * because their stack-size is now based on pointers. Hence breaking the type
  * loop required for computing the byte size of types.
+ *
  * The reason for these type shenanigans is because PDL is a value-based
  * language, but we would still like to be able to express recursively defined
  * types like trees or linked lists. Hence we need to insert pointers somewhere
  * to break these cycles.
+ *
  * We will insert these pointers into the variants of unions. However note that
  * we can only compute the stack size of a union until we've looked at *all*
  * variants. Hence we perform an initial pass where we detect type loops, a
  * second pass where we compute the stack sizes of everything, and a third pass
  * where we actually compute the size of the heap allocations for unions.
+ *
  * As a final bit of global documentation: non-polymorphic types will always
  * have one "monomorph" entry. This contains the non-polymorphic type's memory
  * layout.
  */
 use std::collections::HashMap;
 use std::hash::{Hash, Hasher};
 use crate::protocol::ast::*;
 use crate::protocol::parser::symbol_table::SymbolScope;
 use crate::protocol::input_source::ParseError;
 use crate::protocol::parser::*;
 //------------------------------------------------------------------------------
 // Defined Types
 //------------------------------------------------------------------------------
 /// Struct wrapping around a potentially polymorphic type. If the type does not
 /// have any polymorphic arguments then it will not have any monomorphs and
 /// `is_polymorph` will be set to `false`. A type with polymorphic arguments
 /// only has `is_polymorph` set to `true` if the polymorphic arguments actually
 /// appear in the types associated types (function return argument, struct
 /// field, enum variant, etc.). Otherwise the polymorphic argument is just a
 /// marker and does not influence the bytesize of the type.
 pub struct DefinedType {
     pub(crate) ast_root: RootId,
     pub(crate) ast_definition: DefinitionId,
     pub(crate) definition: DefinedTypeVariant,
     pub(crate) poly_vars: Vec<PolymorphicVariable>,
     pub(crate) is_polymorph: bool,
+}
 pub enum DefinedTypeVariant {
     Enum(EnumType),
     Union(UnionType),
     Struct(StructType),
     Procedure(ProcedureType),
+}
 impl DefinedTypeVariant {
     pub(crate) fn is_data_type(&self) -> bool {
         use DefinedTypeVariant as DTV;
         match self {
             DTV::Struct(_) | DTV::Enum(_) | DTV::Union(_) => return true,
             DTV::Procedure(_) => return false,
+        }
+    }
     pub(crate) fn as_struct(&self) -> &StructType {
         match self {
             DefinedTypeVariant::Struct(v) => v,
             _ => unreachable!()
+        }
+    }
     pub(crate) fn as_enum(&self) -> &EnumType {
         match self {
             DefinedTypeVariant::Enum(v) => v,
             _ => unreachable!()
+        }
+    }
     pub(crate) fn as_union(&self) -> &UnionType {
         match self {
             DefinedTypeVariant::Union(v) => v,
             _ => unreachable!()
+        }
+    }
+}
 pub struct PolymorphicVariable {
     pub(crate) identifier: Identifier,
     pub(crate) is_in_use: bool, // a polymorphic argument may be defined, but not used by the type definition
+}
 /// `EnumType` is the classical C/C++ enum type. It has various variants with
 /// an assigned integer value. The integer values may be user-defined,
 /// compiler-defined, or a mix of the two. If a user assigns the same enum
 /// value multiple times, we assume the user is an expert and we consider both
 /// variants to be equal to one another.
 pub struct EnumType {
     pub variants: Vec<EnumVariant>,
     pub minimum_tag_value: i64,
     pub maximum_tag_value: i64,
     pub tag_type: ConcreteType,
     pub size: usize,
     pub alignment: usize,
+}
 // TODO: Also support maximum u64 value
 pub struct EnumVariant {
     pub identifier: Identifier,
     pub value: i64,
+}
 /// `UnionType` is the algebraic datatype (or sum type, or discriminated union).
 /// A value is an element of the union, identified by its tag, and may contain
 /// a single subtype.
 /// For potentially infinite types (i.e. a tree, or a linked list) only unions
 /// can break the infinite cycle. So when we lay out these unions in memory we
 /// will reserve enough space on the stack for all union variants that do not
 /// cause "type loops" (i.e. a union `A` with a variant containing a struct
 /// `B`). And we will reserve enough space on the heap (and store a pointer in
 /// the union) for all variants which do cause type loops (i.e. a union `A`
 /// with a variant to a struct `B` that contains the union `A` again).
 pub struct UnionType {
     pub variants: Vec<UnionVariant>,
     pub tag_type: ConcreteType,
     pub tag_size: usize,
+}
 pub struct UnionVariant {
     pub identifier: Identifier,
     pub embedded: Vec<ParserType>, // zero-length does not have embedded values
     pub tag_value: i64,
+}
 /// `StructType` is a generic C-like struct type (or record type, or product
 /// type) type.
 pub struct StructType {
     pub fields: Vec<StructField>,
+}
 pub struct StructField {
     pub identifier: Identifier,
     pub parser_type: ParserType,
+}
 /// `ProcedureType` is the signature of a procedure/component
 pub struct ProcedureType {
     pub kind: ProcedureKind,
     pub return_type: Option<ParserType>,
     pub arguments: Vec<ProcedureArgument>,
+}
 pub struct ProcedureArgument {
     identifier: Identifier,
     parser_type: ParserType,
+}
 /// Represents the data associated with a single expression after type inference
 /// for a monomorph (or just the normal expression types, if dealing with a
 /// non-polymorphic function/component).
 pub struct MonomorphExpression {
     // The output type of the expression. Note that for a function it is not the
     // function's signature but its return type
     pub(crate) expr_type: ConcreteType,
     // Has multiple meanings: the field index for select expressions, the
     // monomorph index for polymorphic function calls or literals. Negative
     // values are never used, but used to catch programming errors.
     pub(crate) field_or_monomorph_idx: i32,
     pub(crate) type_id: TypeId,
+}
 //------------------------------------------------------------------------------
 // Type monomorph storage
 //------------------------------------------------------------------------------
 pub(crate) enum MonoTypeVariant {
     Builtin, // no extra data, added manually in compiler initialization code
     Enum, // no extra data
     Struct(StructMonomorph),
     Union(UnionMonomorph),
     Procedure(ProcedureMonomorph), // functions, components
     Tuple(TupleMonomorph),
+}
 impl MonoTypeVariant {
     fn as_struct_mut(&mut self) -> &mut StructMonomorph {
         match self {
             MonoTypeVariant::Struct(v) => v,
             _ => unreachable!(),
+        }
+    }
     pub(crate) fn as_union(&self) -> &UnionMonomorph {
         match self {
             MonoTypeVariant::Union(v) => v,
             _ => unreachable!(),
+        }
+    }
     fn as_union_mut(&mut self) -> &mut UnionMonomorph {
         match self {
             MonoTypeVariant::Union(v) => v,
             _ => unreachable!(),
+        }
+    }
     fn as_tuple_mut(&mut self) -> &mut TupleMonomorph {
         match self {
             MonoTypeVariant::Tuple(v) => v,
             _ => unreachable!(),
+        }
+    }
     pub(crate) fn as_procedure(&self) -> &ProcedureMonomorph {
         match self {
             MonoTypeVariant::Procedure(v) => v,
             _ => unreachable!(),
+        }
+    }
     fn as_procedure_mut(&mut self) -> &mut ProcedureMonomorph {
         match self {
             MonoTypeVariant::Procedure(v) => v,
             _ => unreachable!(),
+        }
+    }
+}
 /// Struct monomorph
 pub struct StructMonomorph {
     pub fields: Vec<StructMonomorphField>,
+}
 pub struct StructMonomorphField {
     pub type_id: TypeId,
     concrete_type: ConcreteType,
     pub size: usize,
     pub alignment: usize,
     pub offset: usize,
+}
 /// Union monomorph
 pub struct UnionMonomorph {
     pub variants: Vec<UnionMonomorphVariant>,
     pub tag_size: usize, // copied from `UnionType` upon monomorph construction.
     // note that the stack size is in the `TypeMonomorph` struct. This size and
     // alignment will include the size of the union tag.
     //
     // heap_size contains the allocated size of the union in the case it
     // is used to break a type loop. If it is 0, then it doesn't require
     // allocation and lives entirely on the stack.
     pub heap_size: usize,
     pub heap_alignment: usize,
+}
 pub struct UnionMonomorphVariant {
     pub lives_on_heap: bool,
     pub embedded: Vec<UnionMonomorphEmbedded>,
+}
 pub struct UnionMonomorphEmbedded {
     pub type_id: TypeId,
     concrete_type: ConcreteType,
     // Note that the meaning of the offset (and alignment) depend on whether or
     // not the variant lives on the stack/heap. If it lives on the stack then
     // they refer to the offset from the start of the union value (so the first
     // embedded type lives at a non-zero offset, because the union tag sits in
     // the front). If it lives on the heap then it refers to the offset from the
     // allocated memory region (so the first embedded type lives at a 0 offset).
     pub size: usize,
     pub alignment: usize,
     pub offset: usize,
+}
 /// Procedure (functions and components of all possible types) monomorph. Also
 /// stores the expression type data from the typechecking/inferencing pass.
 pub struct ProcedureMonomorph {
     pub monomorph_index: u32,
     pub builtin: bool,
+}
 /// Tuple monomorph. Again a kind of exception because one cannot define a named
 /// tuple type containing explicit polymorphic variables. But again: we need to
 /// store size/offset/alignment information, so we do it here.
 pub struct TupleMonomorph {
     pub members: Vec<TupleMonomorphMember>
+}
 pub struct TupleMonomorphMember {
     pub type_id: TypeId,
     concrete_type: ConcreteType,
     pub size: usize,
     pub alignment: usize,
     pub offset: usize,
+}
 /// Generic unique type ID. Every monomorphed type and every non-polymorphic
 /// type will have one of these associated with it.
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub struct TypeId(i64);
 impl TypeId {
     pub(crate) fn new_invalid() -> Self {
         return Self(-1);
+    }
+}
 /// A monomorphed type (or non-polymorphic type's) memory layout and information
 /// regarding associated types (like a struct's field type).
 pub struct MonoType {
     pub type_id: TypeId,
     pub concrete_type: ConcreteType,
     pub size: usize,
     pub alignment: usize,
     pub(crate) variant: MonoTypeVariant
+}
 impl MonoType {
     #[inline]
     fn new_empty(type_id: TypeId, concrete_type: ConcreteType, variant: MonoTypeVariant) -> Self {
         return Self {
             type_id, concrete_type,
             size: 0,
             alignment: 0,
             variant,
+        }
+    }
     /// Little internal helper function as a reminder: if alignment is 0, then
     /// the size/alignment are not actually computed yet!
     #[inline]
     fn get_size_alignment(&self) -> Option<(usize, usize)> {
         if self.alignment == 0 {
             return None
         } else {
             return Some((self.size, self.alignment));
+        }
+    }
+}
 /// Special structure that acts like the lookup key for `ConcreteType` instances
 /// that have already been added to the type table before.
 #[derive(Clone)]
 struct MonoSearchKey {
     // Uses bitflags to denote when parts between search keys should match and
     // whether they should be checked. Needs to have a system like this to
     // accommodate tuples.
     parts: Vec<(u8, ConcreteTypePart)>,
     change_bit: u8,
+}
 impl MonoSearchKey {
     const KEY_IN_USE: u8 = 0x01;
     const KEY_CHANGE_BIT: u8 = 0x02;
     fn with_capacity(capacity: usize) -> Self {
         return MonoSearchKey{
             parts: Vec::with_capacity(capacity),
             change_bit: 0,
         };
+    }
     /// Sets the search key based on a single concrete type and its polymorphic
     /// variables.
     fn set(&mut self, concrete_type_parts: &[ConcreteTypePart], poly_var_in_use: &[PolymorphicVariable]) {
         self.set_top_type(concrete_type_parts[0]);
         let mut poly_var_index = 0;
         for subtype in ConcreteTypeIter::new(concrete_type_parts, 0) {
             let in_use = poly_var_in_use[poly_var_index].is_in_use;
             poly_var_index += 1;
             self.push_subtype(subtype, in_use);
+        }
         debug_assert_eq!(poly_var_index, poly_var_in_use.len());
+    }
     /// Starts setting the search key based on an initial top-level type,
     /// programmer must call `push_subtype` the appropriate number of times
     /// after calling this function
     fn set_top_type(&mut self, type_part: ConcreteTypePart) {
         self.parts.clear();
         self.parts.push((Self::KEY_IN_USE, type_part));
         self.change_bit = Self::KEY_CHANGE_BIT;
+    }
     fn push_subtype(&mut self, concrete_type: &[ConcreteTypePart], in_use: bool) {
         let flag = self.change_bit | (if in_use { Self::KEY_IN_USE } else { 0 });
         for part in concrete_type {
             self.parts.push((flag, *part));
+        }
         self.change_bit ^= Self::KEY_CHANGE_BIT;
+    }
     fn push_subtree(&mut self, concrete_type: &[ConcreteTypePart], poly_var_in_use: &[PolymorphicVariable]) {
         self.parts.push((self.change_bit | Self::KEY_IN_USE, concrete_type[0]));
         self.change_bit ^= Self::KEY_CHANGE_BIT;
         let mut poly_var_index = 0;
         for subtype in ConcreteTypeIter::new(concrete_type, 0) {
             let in_use = poly_var_in_use[poly_var_index].is_in_use;
             poly_var_index += 1;
             self.push_subtype(subtype, in_use);
+        }
         debug_assert_eq!(poly_var_index, poly_var_in_use.len());
+    }
     // Utilities for hashing and comparison
     fn find_end_index(&self, start_index: usize) -> usize {
         // Check if we're already at the end
         let mut index = start_index;
         if index >= self.parts.len() {
             return index;
+        }
         // Iterate until bit flips, or until at end
         let expected_bit = self.parts[index].0 & Self::KEY_CHANGE_BIT;
         index += 1;
         while index < self.parts.len() {
             let current_bit = self.parts[index].0 & Self::KEY_CHANGE_BIT;
             if current_bit != expected_bit {
                 return index;
+            }
             index += 1;
+        }
         return index;
+    }
+}
 impl Hash for MonoSearchKey {
     fn hash<H: Hasher>(&self, state: &mut H) {
         for index in 0..self.parts.len() {
             let (flags, part) = self.parts[index];
             if flags & Self::KEY_IN_USE != 0 {
                 part.hash(state);
+            }
+        }
+    }
+}
 impl PartialEq for MonoSearchKey {
     fn eq(&self, other: &Self) -> bool {
         let mut self_index = 0;
         let mut other_index = 0;
         while self_index < self.parts.len() && other_index < other.parts.len() {
             // Retrieve part and flags
             let (self_bits, _) = self.parts[self_index];
             let (other_bits, _) = other.parts[other_index];
             let self_in_use = (self_bits & Self::KEY_IN_USE) != 0;
             let other_in_use = (other_bits & Self::KEY_IN_USE) != 0;
             // Determine ending indices
             let self_end_index = self.find_end_index(self_index);
             let other_end_index = other.find_end_index(other_index);
             if self_in_use == other_in_use {
                 if self_in_use {
                     // Both are in use, so both parts should be equal
                     let delta_self = self_end_index - self_index;
                     let delta_other = other_end_index - other_index;
                     if delta_self != delta_other {
                         // Both in use, but not of equal length, so the types
                         // cannot match
                         return false;
+                    }
                     for _ in 0..delta_self {
                         let (_, self_part) = self.parts[self_index];
                         let (_, other_part) = other.parts[other_index];
                         if self_part != other_part {
                             return false;
+                        }
                         self_index += 1;
                         other_index += 1;
+                    }
                 } else {
                     // Both not in use, so skip associated parts
                     self_index = self_end_index;
                     other_index = other_end_index;
+                }
             } else {
                 // No agreement on importance of parts. This is practically
                 // impossible
                 unreachable!();
+            }
+        }
         // Everything matched, so if we're at the end of both arrays then we're
         // certain that the two keys are equal.
         return self_index == self.parts.len() && other_index == other.parts.len();
+    }
+}
 impl Eq for MonoSearchKey{}
 //------------------------------------------------------------------------------
 // Type table
 //------------------------------------------------------------------------------
 const POLY_VARS_IN_USE: [PolymorphicVariable; 1] = [PolymorphicVariable{ identifier: Identifier::new_empty(InputSpan::new()), is_in_use: true }];
 // Programmer note: keep this struct free of dynamically allocated memory
 #[derive(Clone)]
 struct TypeLoopBreadcrumb {
     type_id: TypeId,
     next_member: u32,
     next_embedded: u32, // for unions, the index into the variant's embedded types
+}
 // Programmer note: keep this struct free of dynamically allocated memory
 #[derive(Clone)]
 struct MemoryBreadcrumb {
     type_id: TypeId,
     next_member: u32,
     next_embedded: u32,
     first_size_alignment_idx: u32,
+}
 #[derive(Debug, PartialEq, Eq)]
 enum TypeLoopResult {
     TypeExists,
     PushBreadcrumb(DefinitionId, ConcreteType),
     TypeLoop(usize), // index into vec of breadcrumbs at which the type matched
+}
 enum MemoryLayoutResult {
     TypeExists(usize, usize), // (size, alignment)
     PushBreadcrumb(MemoryBreadcrumb),
+}
 // TODO: @Optimize, initial memory-unoptimized implementation
 struct TypeLoopEntry {
     type_id: TypeId,
     is_union: bool,
+}
 struct TypeLoop {
     members: Vec<TypeLoopEntry>,
+}
 type DefinitionMap = HashMap<DefinitionId, DefinedType>;
 type MonoTypeMap = HashMap<MonoSearchKey, TypeId>;
 type MonoTypeArray = Vec<MonoType>;
 pub struct TypeTable {
     // Lookup from AST DefinitionId to a defined type. Also lookups for
     // concrete type to monomorphs
     pub(crate) definition_lookup: DefinitionMap,
     mono_type_lookup: MonoTypeMap,
     pub(crate) mono_types: MonoTypeArray,
     mono_search_key: MonoSearchKey,
     // Breadcrumbs left behind while trying to find type loops. Also used to
     // determine sizes of types when all type loops are detected.
     type_loop_breadcrumbs: Vec<TypeLoopBreadcrumb>,
     type_loops: Vec<TypeLoop>,
     // Stores all encountered types during type loop detection. Used afterwards
     // to iterate over all types in order to compute size/alignment.
     encountered_types: Vec<TypeLoopEntry>,
     // Breadcrumbs and temporary storage during memory layout computation.
     memory_layout_breadcrumbs: Vec<MemoryBreadcrumb>,
     size_alignment_stack: Vec<(usize, usize)>,
+}
 impl TypeTable {
     /// Construct a new type table without any resolved types.
     pub(crate) fn new() -> Self {
         Self{
             definition_lookup: HashMap::with_capacity(128),
             mono_type_lookup: HashMap::with_capacity(128),
             mono_types: Vec::with_capacity(128),
             mono_search_key: MonoSearchKey::with_capacity(32),
             type_loop_breadcrumbs: Vec::with_capacity(32),
             type_loops: Vec::with_capacity(8),
             encountered_types: Vec::with_capacity(32),
             memory_layout_breadcrumbs: Vec::with_capacity(32),
             size_alignment_stack: Vec::with_capacity(64),
+        }
+    }
     /// Iterates over all defined types (polymorphic and non-polymorphic) and
     /// add their types in two passes. In the first pass we will just add the
     /// base types (we will not consider monomorphs, and we will not compute
     /// byte sizes). In the second pass we will compute byte sizes of
     /// non-polymorphic types, and potentially the monomorphs that are embedded
     /// in those types.
     pub(crate) fn build_base_types(&mut self, modules: &mut [Module], ctx: &mut PassCtx) -> Result<(), ParseError> {
         // Make sure we're allowed to cast root_id to index into ctx.modules
         debug_assert!(modules.iter().all(|m| m.phase >= ModuleCompilationPhase::DefinitionsParsed));
         debug_assert!(self.definition_lookup.is_empty());
         dbg_code!({
             for (index, module) in modules.iter().enumerate() {
                 debug_assert_eq!(index, module.root_id.index as usize);
+            }
         });
         // Use context to guess hashmap size of the base types
         let reserve_size = ctx.heap.definitions.len();
         self.definition_lookup.reserve(reserve_size);
         // Resolve all base types
         for definition_idx in 0..ctx.heap.definitions.len() {
             let definition_id = ctx.heap.definitions.get_id(definition_idx);
             let definition = &ctx.heap[definition_id];
             match definition {
                 Definition::Enum(_) => self.build_base_enum_definition(modules, ctx, definition_id)?,
                 Definition::Union(_) => self.build_base_union_definition(modules, ctx, definition_id)?,
                 Definition::Struct(_) => self.build_base_struct_definition(modules, ctx, definition_id)?,
                 Definition::Procedure(_) => self.build_base_procedure_definition(modules, ctx, definition_id)?,
+            }
+        }
         debug_assert_eq!(self.definition_lookup.len(), reserve_size, "mismatch in reserved size of type table");
         for module in modules.iter_mut() {
             module.phase = ModuleCompilationPhase::TypesAddedToTable;
+        }
         // Go through all types again, lay out all types that are not
         // polymorphic. This might cause us to lay out monomorphized polymorphs
         // if these were member types of non-polymorphic types.
         for definition_idx in 0..ctx.heap.definitions.len() {
             let definition_id = ctx.heap.definitions.get_id(definition_idx);
             let poly_type = self.definition_lookup.get(&definition_id).unwrap();
             if !poly_type.definition.is_data_type() || !poly_type.poly_vars.is_empty() {
                 continue;
+            }
             // If here then the type is a data type without polymorphic
             // variables, but we might have instantiated it already, so:
             let concrete_parts = [ConcreteTypePart::Instance(definition_id, 0)];
             self.mono_search_key.set(&concrete_parts, &[]);
             let type_id = self.mono_type_lookup.get(&self.mono_search_key);
             if type_id.is_none() {
                 self.detect_and_resolve_type_loops_for(
                     modules, ctx.heap, ctx.arch,
                     ConcreteType{
                         parts: vec![ConcreteTypePart::Instance(definition_id, 0)]
                     },
                 )?;
                 self.lay_out_memory_for_encountered_types(ctx.arch);
+            }
+        }
         Ok(())
+    }
     /// Retrieves base definition from type table. We must be able to retrieve
     /// it as we resolve all base types upon type table construction (for now).
     /// However, in the future we might do on-demand type resolving, so return
     /// an option anyway
     #[inline]
     pub(crate) fn get_base_definition(&self, definition_id: &DefinitionId) -> Option<&DefinedType> {
         self.definition_lookup.get(&definition_id)
+    }
     /// Returns the index into the monomorph type array if the procedure type
     /// already has a (reserved) monomorph.
     #[inline]
     pub(crate) fn get_procedure_monomorph_type_id(&self, definition_id: &DefinitionId, type_parts: &[ConcreteTypePart]) -> Option<TypeId> {
         // Cannot use internal search key due to mutability issues. But this
         // method should end up being deprecated at some point anyway.
         debug_assert_eq!(get_concrete_type_definition(type_parts).unwrap(), *definition_id);
         let base_type = self.definition_lookup.get(definition_id).unwrap();
         let mut search_key = MonoSearchKey::with_capacity(type_parts.len());
         search_key.set(type_parts, &base_type.poly_vars);
         return self.mono_type_lookup.get(&search_key).copied();
+    }
     #[inline]
     pub(crate) fn get_monomorph(&self, type_id: TypeId) -> &MonoType {
         return &self.mono_types[type_id.0 as usize];
+    }
     /// Reserves space for a monomorph of a polymorphic procedure. The index
     /// will point into a (reserved) slot of the array of expression types. The
     /// monomorph may NOT exist yet (because the reservation implies that we're
     /// going to be performing typechecking on it, and we don't want to
     /// check the same monomorph twice)
     pub(crate) fn reserve_procedure_monomorph_type_id(&mut self, definition_id: &DefinitionId, concrete_type: ConcreteType, monomorph_index: u32) -> TypeId {
         debug_assert_eq!(get_concrete_type_definition(&concrete_type.parts).unwrap(), *definition_id);
         let type_id = TypeId(self.mono_types.len() as i64);
         let base_type = self.definition_lookup.get_mut(definition_id).unwrap();
         self.mono_search_key.set(&concrete_type.parts, &base_type.poly_vars);
         debug_assert!(!self.mono_type_lookup.contains_key(&self.mono_search_key));
         self.mono_type_lookup.insert(self.mono_search_key.clone(), type_id);
         self.mono_types.push(MonoType::new_empty(type_id, concrete_type, MonoTypeVariant::Procedure(ProcedureMonomorph{
             monomorph_index,
             builtin: false,
         })));
         return type_id;
+    }
     /// Adds a builtin type to the type table. As this is only called by the
     /// compiler during setup we assume it cannot fail.
     pub(crate) fn add_builtin_data_type(&mut self, concrete_type: ConcreteType, poly_vars: &[PolymorphicVariable], size: usize, alignment: usize) -> TypeId {
         self.mono_search_key.set(&concrete_type.parts, poly_vars);
         debug_assert!(!self.mono_type_lookup.contains_key(&self.mono_search_key));
         debug_assert_ne!(alignment, 0);
         let type_id = TypeId(self.mono_types.len() as i64);
         self.mono_type_lookup.insert(self.mono_search_key.clone(), type_id);
         self.mono_types.push(MonoType{
             type_id,
             concrete_type,
             size,
             alignment,
             variant: MonoTypeVariant::Builtin,
         });
         return type_id;
+    }
     /// Adds a builtin procedure to the type table.
     pub(crate) fn add_builtin_procedure_type(&mut self, concrete_type: ConcreteType, poly_vars: &[PolymorphicVariable]) -> TypeId {
         self.mono_search_key.set(&concrete_type.parts, poly_vars);
         debug_assert!(!self.mono_type_lookup.contains_key(&self.mono_search_key));
         let type_id = TypeId(self.mono_types.len() as i64);
         self.mono_type_lookup.insert(self.mono_search_key.clone(), type_id);
         self.mono_types.push(MonoType{
             type_id,
             concrete_type,
             size: 0,
             alignment: 0,
             variant: MonoTypeVariant::Procedure(ProcedureMonomorph{
                 monomorph_index: u32::MAX,
                 builtin: true,
             })
         });
         return type_id;
+    }
     /// Adds a monomorphed type to the type table. If it already exists then the
     /// previous entry will be used.
     pub(crate) fn add_monomorphed_type(
         &mut self, modules: &[Module], heap: &Heap, arch: &TargetArch, concrete_type: ConcreteType
     ) -> Result<TypeId, ParseError> {
         // Check if the concrete type was already added
         Self::set_search_key_to_type(&mut self.mono_search_key, &self.definition_lookup, &concrete_type.parts);
         if let Some(type_id) = self.mono_type_lookup.get(&self.mono_search_key) {
             return Ok(*type_id);
+        }
         // Concrete type needs to be added
         self.detect_and_resolve_type_loops_for(modules, heap, arch, concrete_type)?;
         let type_id = self.encountered_types[0].type_id;
         self.lay_out_memory_for_encountered_types(arch);
         return Ok(type_id);
+    }
     //--------------------------------------------------------------------------
     // Building base types
     //--------------------------------------------------------------------------
     /// Builds the base type for an enum. Will not compute byte sizes
     fn build_base_enum_definition(&mut self, modules: &[Module], ctx: &mut PassCtx, definition_id: DefinitionId) -> Result<(), ParseError> {
         debug_assert!(!self.definition_lookup.contains_key(&definition_id), "base enum already built");
         let definition = ctx.heap[definition_id].as_enum();
         let root_id = definition.defined_in;
         // Determine enum variants
         let mut enum_value = -1;
         let mut variants = Vec::with_capacity(definition.variants.len());
         for variant in &definition.variants {
             if enum_value == i64::MAX {
                 let source = &modules[definition.defined_in.index as usize].source;
                 return Err(ParseError::new_error_str_at_span(
                     source, variant.identifier.span,
                     "this enum variant has an integer value that is too large"
                 ));
+            }
             enum_value += 1;
             if let EnumVariantValue::Integer(explicit_value) = variant.value {
                 enum_value = explicit_value;
+            }
             variants.push(EnumVariant{
                 identifier: variant.identifier.clone(),
                 value: enum_value,
             });
+        }
         // Determine tag size
         let mut min_enum_value = 0;
         let mut max_enum_value = 0;
         if !variants.is_empty() {
             min_enum_value = variants[0].value;
             max_enum_value = variants[0].value;
             for variant in variants.iter().skip(1) {
                 min_enum_value = min_enum_value.min(variant.value);
                 max_enum_value = max_enum_value.max(variant.value);
+            }
+        }
         let (tag_type, size_and_alignment) = Self::variant_tag_type_from_values(min_enum_value, max_enum_value);
         // Enum names and polymorphic args do not conflict
         Self::check_identifier_collision(
             modules, root_id, &variants, |variant| &variant.identifier, "enum variant"
         )?;
         // Polymorphic arguments cannot appear as embedded types, because
         // they can only consist of integer variants.
         Self::check_poly_args_collision(modules, ctx, root_id, &definition.poly_vars)?;
         let poly_vars = Self::create_polymorphic_variables(&definition.poly_vars);
         self.definition_lookup.insert(definition_id, DefinedType {
             ast_root: root_id,
             ast_definition: definition_id,
             definition: DefinedTypeVariant::Enum(EnumType{
                 variants,
                 minimum_tag_value: min_enum_value,
                 maximum_tag_value: max_enum_value,
                 tag_type,
                 size: size_and_alignment,
                 alignment: size_and_alignment
             }),
             poly_vars,
             is_polymorph: false,
         });
         return Ok(());
+    }
     /// Builds the base type for a union. Will compute byte sizes.
     fn build_base_union_definition(&mut self, modules: &[Module], ctx: &mut PassCtx, definition_id: DefinitionId) -> Result<(), ParseError> {
         debug_assert!(!self.definition_lookup.contains_key(&definition_id), "base union already built");
         let definition = ctx.heap[definition_id].as_union();
         let root_id = definition.defined_in;
         // Check all variants and their embedded types
         let mut variants = Vec::with_capacity(definition.variants.len());
         let mut tag_counter = 0;
         for variant in &definition.variants {
             for embedded in &variant.value {
                 Self::check_member_parser_type(
                     modules, ctx, root_id, embedded, false
                 )?;
+            }
             variants.push(UnionVariant{
                 identifier: variant.identifier.clone(),
                 embedded: variant.value.clone(),
                 tag_value: tag_counter,
             });
             tag_counter += 1;
+        }
         let mut max_tag_value = 0;
         if tag_counter != 0 {
             max_tag_value = tag_counter - 1
+        }
         let (tag_type, tag_size) = Self::variant_tag_type_from_values(0, max_tag_value);
         // Make sure there are no conflicts in identifiers
         Self::check_identifier_collision(
             modules, root_id, &variants, |variant| &variant.identifier, "union variant"
         )?;
         Self::check_poly_args_collision(modules, ctx, root_id, &definition.poly_vars)?;
         // Construct internal representation of union
         let mut poly_vars = Self::create_polymorphic_variables(&definition.poly_vars);
         for variant in &definition.variants {
             for embedded in &variant.value {
                 Self::mark_used_polymorphic_variables(&mut poly_vars, embedded);
+            }
+        }
         let is_polymorph = poly_vars.iter().any(|arg| arg.is_in_use);
         self.definition_lookup.insert(definition_id, DefinedType{
             ast_root: root_id,
             ast_definition: definition_id,
             definition: DefinedTypeVariant::Union(UnionType{ variants, tag_type, tag_size }),
             poly_vars,
             is_polymorph
         });
         return Ok(());
+    }
     /// Builds base struct type. Will not compute byte sizes.
     fn build_base_struct_definition(&mut self, modules: &[Module], ctx: &mut PassCtx, definition_id: DefinitionId) -> Result<(), ParseError> {
         debug_assert!(!self.definition_lookup.contains_key(&definition_id), "base struct already built");
         let definition = ctx.heap[definition_id].as_struct();
         let root_id = definition.defined_in;
         // Check all struct fields and construct internal representation
         let mut fields = Vec::with_capacity(definition.fields.len());
         for field in &definition.fields {
             Self::check_member_parser_type(
                 modules, ctx, root_id, &field.parser_type, false
             )?;
             fields.push(StructField{
                 identifier: field.field.clone(),
                 parser_type: field.parser_type.clone(),
             });
+        }
         // Make sure there are no conflicting variables
         Self::check_identifier_collision(
             modules, root_id, &fields, |field| &field.identifier, "struct field"
         )?;
         Self::check_poly_args_collision(modules, ctx, root_id, &definition.poly_vars)?;
         // Construct base type in table
         let mut poly_vars = Self::create_polymorphic_variables(&definition.poly_vars);
         for field in &fields {
             Self::mark_used_polymorphic_variables(&mut poly_vars, &field.parser_type);
+        }
         let is_polymorph = poly_vars.iter().any(|arg| arg.is_in_use);
         self.definition_lookup.insert(definition_id, DefinedType{
             ast_root: root_id,
             ast_definition: definition_id,
             definition: DefinedTypeVariant::Struct(StructType{ fields }),
             poly_vars,
             is_polymorph
         });
         return Ok(())
+    }
     /// Builds base procedure type.
     fn build_base_procedure_definition(&mut self, modules: &[Module], ctx: &mut PassCtx, definition_id: DefinitionId) -> Result<(), ParseError> {
         debug_assert!(!self.definition_lookup.contains_key(&definition_id), "base function already built");
         let definition = ctx.heap[definition_id].as_procedure();
         let root_id = definition.defined_in;
         // Check and construct return types and argument types.
         if let Some(return_type) = &definition.return_type {
             Self::check_member_parser_type(
                 modules, ctx, root_id, return_type, definition.builtin
             )?;
+        }
         let mut arguments = Vec::with_capacity(definition.parameters.len());
         for parameter_id in &definition.parameters {
             let parameter = &ctx.heap[*parameter_id];
             Self::check_member_parser_type(
                 modules, ctx, root_id, &parameter.parser_type, definition.builtin
             )?;
             arguments.push(ProcedureArgument{
                 identifier: parameter.identifier.clone(),
                 parser_type: parameter.parser_type.clone(),
             });
+        }
         // Check conflict of identifiers
         Self::check_identifier_collision(
             modules, root_id, &arguments, |arg| &arg.identifier, "procedure argument"
         )?;
         Self::check_poly_args_collision(modules, ctx, root_id, &definition.poly_vars)?;
         // Construct internal representation of function type
         // TODO: Marking used polymorphic variables should take statements in
         //  the body into account. But currently we don't. Hence mark them all
         //  as being in-use. Note to self: true condition should be that the
         //  polymorphic variables are used in places where the resulting types
         //  are themselves truly polymorphic types (e.g. not a phantom type).
         let mut poly_vars = Self::create_polymorphic_variables(&definition.poly_vars);
         for poly_var in &mut poly_vars {
             poly_var.is_in_use = true;
+        }
         let is_polymorph = poly_vars.iter().any(|arg| arg.is_in_use);
         self.definition_lookup.insert(definition_id, DefinedType{
             ast_root: root_id,
             ast_definition: definition_id,
             definition: DefinedTypeVariant::Procedure(ProcedureType{
                 kind: definition.kind,
                 return_type: definition.return_type.clone(),
                 arguments
             }),
             poly_vars,
             is_polymorph
         });
         return Ok(());
+    }
     /// Will check if the member type (field of a struct, embedded type in a
     /// union variant) is valid.
     fn check_member_parser_type(
         modules: &[Module], ctx: &PassCtx, base_definition_root_id: RootId,
         member_parser_type: &ParserType, allow_special_compiler_types: bool
     ) -> Result<(), ParseError> {
         use ParserTypeVariant as PTV;
         for element in &member_parser_type.elements {
             match element.variant {
                 // Special cases
                 PTV::Void | PTV::InputOrOutput | PTV::ArrayLike | PTV::IntegerLike => {
                     if !allow_special_compiler_types {
                         unreachable!("compiler-only ParserTypeVariant in member type");
+                    }
                 },
                 // Builtin types, always valid
                 PTV::Message | PTV::Bool |
                 PTV::UInt8 | PTV::UInt16 | PTV::UInt32 | PTV::UInt64 |
                 PTV::SInt8 | PTV::SInt16 | PTV::SInt32 | PTV::SInt64 |
                 PTV::Character | PTV::String |
                 PTV::Array | PTV::Input | PTV::Output | PTV::Tuple(_) |
                 // Likewise, polymorphic variables are always valid
                 PTV::PolymorphicArgument(_, _) => {},
                 // Types that are not constructable, or types that are not
                 // allowed (and checked earlier)
                 PTV::IntegerLiteral | PTV::Inferred => {
                     unreachable!("illegal ParserTypeVariant within type definition");
                 },
                 // Finally, user-defined types
                 PTV::Definition(definition_id, _) => {
                     let definition = &ctx.heap[definition_id];
                     if !(definition.is_struct() || definition.is_enum() || definition.is_union()) {
                         let source = &modules[base_definition_root_id.index as usize].source;
                         return Err(ParseError::new_error_str_at_span(
                             source, element.element_span, "expected a datatype (a struct, enum or union)"
                         ));
+                    }
                     // Otherwise, we're fine
+                }
+            }
+        }
         // If here, then all elements check out
         return Ok(());
+    }
     /// Go through a list of identifiers and ensure that all identifiers have
     /// unique names
     fn check_identifier_collision<T: Sized, F: Fn(&T) -> &Identifier>(
         modules: &[Module], root_id: RootId, items: &[T], getter: F, item_name: &'static str
     ) -> Result<(), ParseError> {
         for (item_idx, item) in items.iter().enumerate() {
             let item_ident = getter(item);
             for other_item in &items[0..item_idx] {
                 let other_item_ident = getter(other_item);
                 if item_ident == other_item_ident {
                     let module_source = &modules[root_id.index as usize].source;
                     return Err(ParseError::new_error_at_span(
                         module_source, item_ident.span, format!("This {} is defined more than once", item_name)
                     ).with_info_at_span(
                         module_source, other_item_ident.span, format!("The other {} is defined here", item_name)
                     ));
+                }
+            }
+        }
         Ok(())
+    }
     /// Go through a list of polymorphic arguments and make sure that the
     /// arguments all have unique names, and the arguments do not conflict with
     /// any symbols defined at the module scope.
     fn check_poly_args_collision(
         modules: &[Module], ctx: &PassCtx, root_id: RootId, poly_args: &[Identifier]
     ) -> Result<(), ParseError> {
         // Make sure polymorphic arguments are unique and none of the
         // identifiers conflict with any imported scopes
         for (arg_idx, poly_arg) in poly_args.iter().enumerate() {
             for other_poly_arg in &poly_args[..arg_idx] {
                 if poly_arg == other_poly_arg {
                     let module_source = &modules[root_id.index as usize].source;
                     return Err(ParseError::new_error_str_at_span(
                         module_source, poly_arg.span,
                         "This polymorphic argument is defined more than once"
                     ).with_info_str_at_span(
                         module_source, other_poly_arg.span,
                         "It conflicts with this polymorphic argument"
                     ));
+                }
+            }
             // Check if identifier conflicts with a symbol defined or imported
             // in the current module
             if let Some(symbol) = ctx.symbols.get_symbol_by_name(SymbolScope::Module(root_id), poly_arg.value.as_bytes()) {
                 // We have a conflict
                 let module_source = &modules[root_id.index as usize].source;
                 let introduction_span = symbol.variant.span_of_introduction(ctx.heap);
                 return Err(ParseError::new_error_str_at_span(
                     module_source, poly_arg.span,
                     "This polymorphic argument conflicts with another symbol"
                 ).with_info_str_at_span(
                     module_source, introduction_span,
                     "It conflicts due to this symbol"
                 ));
+            }
+        }
         // All arguments are fine
         Ok(())
+    }
     //--------------------------------------------------------------------------
     // Detecting type loops
     //--------------------------------------------------------------------------
     /// Internal function that will detect type loops and check if they're
     /// resolvable. If so then the appropriate union variants will be marked as
     /// "living on heap". If not then a `ParseError` will be returned
     fn detect_and_resolve_type_loops_for(&mut self, modules: &[Module], heap: &Heap, arch: &TargetArch, concrete_type: ConcreteType) -> Result<(), ParseError> {
         // Programmer notes: what happens here is the we call
         // `check_member_for_type_loops` for a particular type's member, and
         // then take action using the return value:
         // 1. It might already be resolved: in this case it implies we don't
         //  have type loops, or they have been resolved.
         // 2. A new type is encountered. If so then it is added to the type loop
         //  breadcrumbs.
         // 3. A type loop is detected (implying the type is already resolved, or
         //  already exists in the type loop breadcrumbs).
         //
         // Using the breadcrumbs we incrementally check every member type of a
         // particular considered type (e.g. a struct field, tuple member), and
         // do the same as above. Note that when a breadcrumb is added we reserve
         // space in the monomorph storage, initialized to zero-values (i.e.
         // wrong values). The breadcrumbs keep track of how far and along we are
         // with resolving the member types.
         //
         // At the end we may have some type loops. If they're unresolvable then
         // we throw an error). If there are no type loops or they are all
         // resolvable then we end up with a list of `encountered_types`. These
         // are then used by `lay_out_memory_for_encountered_types`.
         debug_assert!(self.type_loop_breadcrumbs.is_empty());
         debug_assert!(self.type_loops.is_empty());
         debug_assert!(self.encountered_types.is_empty());
         // Push the initial breadcrumb
         let initial_breadcrumb = Self::check_member_for_type_loops(
             &self.type_loop_breadcrumbs, &self.definition_lookup, &self.mono_type_lookup,
             &mut self.mono_search_key, &concrete_type
         );
         if let TypeLoopResult::PushBreadcrumb(definition_id, concrete_type) = initial_breadcrumb {
             self.handle_new_breadcrumb_for_type_loops(arch, definition_id, concrete_type);
         } else {
             unreachable!()
         };
         // Enter into the main resolving loop
         while !self.type_loop_breadcrumbs.is_empty() {
             // Because we might be modifying the breadcrumb array we need to
             let breadcrumb_idx = self.type_loop_breadcrumbs.len() - 1;
             let mut breadcrumb = self.type_loop_breadcrumbs[breadcrumb_idx].clone();
             let mono_type = &self.mono_types[breadcrumb.type_id.0 as usize];
             let resolve_result = match &mono_type.variant {
                 MonoTypeVariant::Builtin => {
                     TypeLoopResult::TypeExists
+                }
                 MonoTypeVariant::Enum => {
                     TypeLoopResult::TypeExists
                 },
                 MonoTypeVariant::Union(monomorph) => {
                     let num_variants = monomorph.variants.len() as u32;
                     let mut union_result = TypeLoopResult::TypeExists;
                     'member_loop: while breadcrumb.next_member < num_variants {
                         let mono_variant = &monomorph.variants[breadcrumb.next_member as usize];
                         let num_embedded = mono_variant.embedded.len() as u32;
                         while breadcrumb.next_embedded < num_embedded {
                             let mono_embedded = &mono_variant.embedded[breadcrumb.next_embedded as usize];
                             union_result = Self::check_member_for_type_loops(
                                 &self.type_loop_breadcrumbs, &self.definition_lookup, &self.mono_type_lookup,
                                 &mut self.mono_search_key, &mono_embedded.concrete_type
                             );
                             if union_result != TypeLoopResult::TypeExists {
                                 // In type loop or new breadcrumb pushed, so
                                 // break out of the resolving loop
                                 break 'member_loop;
+                            }
                             breadcrumb.next_embedded += 1;
+                        }
                         breadcrumb.next_embedded = 0;
                         breadcrumb.next_member += 1
+                    }
                     union_result
                 },
                 MonoTypeVariant::Struct(monomorph) => {
                     let num_fields = monomorph.fields.len() as u32;
                     let mut struct_result = TypeLoopResult::TypeExists;
                     while breadcrumb.next_member < num_fields {
                         let mono_field = &monomorph.fields[breadcrumb.next_member as usize];
                         struct_result = Self::check_member_for_type_loops(
                             &self.type_loop_breadcrumbs, &self.definition_lookup, &self.mono_type_lookup,
                             &mut self.mono_search_key, &mono_field.concrete_type
                         );
                         if struct_result != TypeLoopResult::TypeExists {
                             // Type loop or breadcrumb pushed, so break out of
                             // the resolving loop
                             break;
+                        }
                         breadcrumb.next_member += 1;
+                    }
                     struct_result
                 },
                 MonoTypeVariant::Procedure(_) => unreachable!(),
                 MonoTypeVariant::Tuple(monomorph) => {
                     let num_members = monomorph.members.len() as u32;
                     let mut tuple_result = TypeLoopResult::TypeExists;
                     while breadcrumb.next_member < num_members {
                         let tuple_member = &monomorph.members[breadcrumb.next_member as usize];
                         tuple_result = Self::check_member_for_type_loops(
                             &self.type_loop_breadcrumbs, &self.definition_lookup, &self.mono_type_lookup,
                             &mut self.mono_search_key, &tuple_member.concrete_type
                         );
                         if tuple_result != TypeLoopResult::TypeExists {
                             break;
+                        }
                         breadcrumb.next_member += 1;
+                    }
                     tuple_result
+                }
             };
             // Handle the result of attempting to resolve the current breadcrumb
             match resolve_result {
                 TypeLoopResult::TypeExists => {
                     // We finished parsing the type
                     self.type_loop_breadcrumbs.pop();
                 },
                 TypeLoopResult::PushBreadcrumb(definition_id, concrete_type) => {
                     // We recurse into the member type.
                     self.type_loop_breadcrumbs[breadcrumb_idx] = breadcrumb;
                     self.handle_new_breadcrumb_for_type_loops(arch, definition_id, concrete_type);
                 },
                 TypeLoopResult::TypeLoop(first_idx) => {
                     // Because we will be modifying breadcrumbs within the
                     // type-loop handling code, put back the modified breadcrumb
                     self.type_loop_breadcrumbs[breadcrumb_idx] = breadcrumb;
                     // We're in a type loop. Add the type loop
                     let mut loop_members = Vec::with_capacity(self.type_loop_breadcrumbs.len() - first_idx);
                     let mut contains_union = false;
                     for breadcrumb_idx in first_idx..self.type_loop_breadcrumbs.len() {
                         let breadcrumb = &mut self.type_loop_breadcrumbs[breadcrumb_idx];
                         let mut is_union = false;
                         // Check if type loop member is a union that may be
                         // broken up by moving some of its members to the heap.
                         let mono_type = &mut self.mono_types[breadcrumb.type_id.0 as usize];
                         if let MonoTypeVariant::Union(union_type) = &mut mono_type.variant {
                             // Mark the variant that caused the loop as heap
                             // allocated to break the type loop.
                             let variant = &mut union_type.variants[breadcrumb.next_member as usize];
                             variant.lives_on_heap = true;
                             breadcrumb.next_embedded += 1;
                             is_union = true;
                             contains_union = true;
                         } // else: we don't care about the type for now
                         loop_members.push(TypeLoopEntry{
                             type_id: breadcrumb.type_id,
                             is_union
                         });
+                    }
                     let new_type_loop = TypeLoop{ members: loop_members };
                     if !contains_union {
                         // No way to (potentially) break the union. So return a
                         // type loop error. This is because otherwise our
                         // breadcrumb resolver ends up in an infinite loop.
                         return Err(construct_type_loop_error(
                             &self.mono_types, &new_type_loop, modules, heap
                         ));
+                    }
                     self.type_loops.push(new_type_loop);
+                }
+            }
+        }
         // All breadcrumbs have been cleared. So now `type_loops` contains all
         // of the encountered type loops, and `encountered_types` contains a
         // list of all unique monomorphs we encountered.
         // The next step is to figure out if all of the type loops can be
         // broken. A type loop can be broken if at least one union exists in the
         // loop and that union ended up having variants that are not part of
         // a type loop.
         fn type_loop_source_span_and_message<'a>(
             modules: &'a [Module], heap: &Heap, mono_types: &MonoTypeArray,
             definition_id: DefinitionId, mono_type_id: TypeId, index_in_loop: usize
         ) -> (&'a InputSource, InputSpan, String) {
             // Note: because we will discover the type loop the *first* time we
             // instantiate a monomorph with the provided polymorphic arguments
             // (not all arguments are actually used in the type). We don't have
             // to care about a second instantiation where certain unused
             // polymorphic arguments are different.
             let mono_type = &mono_types[mono_type_id.0 as usize];
             let type_name = mono_type.concrete_type.display_name(heap);
             let message = if index_in_loop == 0 {
                 format!(
                     "encountered an infinitely large type for '{}' (which can be fixed by \
                     introducing a union type that has a variant whose embedded types are \
                     not part of a type loop, or do not have embedded types)",
                     type_name
+                )
             } else if index_in_loop == 1 {
                 format!("because it depends on the type '{}'", type_name)
             } else {
                 format!("which depends on the type '{}'", type_name)
             };
             let ast_definition = &heap[definition_id];
             let ast_root_id = ast_definition.defined_in();
             return (
                 &modules[ast_root_id.index as usize].source,
                 ast_definition.identifier().span,
                 message
             );
+        }
         fn construct_type_loop_error(mono_types: &MonoTypeArray, type_loop: &TypeLoop, modules: &[Module], heap: &Heap) -> ParseError {
             // Seek first entry to produce parse error. Then continue builder
             // pattern. This is the error case so efficiency can go home.
             let mut parse_error = None;
             let mut next_member_index = 0;
             while next_member_index < type_loop.members.len() {
                 let first_entry = &type_loop.members[next_member_index];
                 next_member_index += 1;
                 // Retrieve definition of first type in loop
                 let first_mono_type = &mono_types[first_entry.type_id.0 as usize];
                 let first_definition_id = get_concrete_type_definition(&first_mono_type.concrete_type.parts);
                 if first_definition_id.is_none() {
                     continue;
+                }
                 let first_definition_id = first_definition_id.unwrap();
                 // Produce error message for first type in loop
                 let (first_module, first_span, first_message) = type_loop_source_span_and_message(
                     modules, heap, mono_types, first_definition_id, first_entry.type_id, 0
                 );
                 parse_error = Some(ParseError::new_error_at_span(first_module, first_span, first_message));
                 break;
+            }
             let mut parse_error = parse_error.unwrap(); // Loop above cannot have failed, because we must have a type loop, type loops cannot contain only unnamed types
             let mut error_counter = 1;
             for member_idx in next_member_index..type_loop.members.len() {
                 let entry = &type_loop.members[member_idx];
                 let mono_type = &mono_types[entry.type_id.0 as usize];
                 let definition_id = get_concrete_type_definition(&mono_type.concrete_type.parts);
                 if definition_id.is_none() {
                     continue;
+                }
                 let definition_id = definition_id.unwrap();
                 let (module, span, message) = type_loop_source_span_and_message(
                     modules, heap, mono_types, definition_id, entry.type_id, error_counter
                 );
                 parse_error = parse_error.with_info_at_span(module, span, message);
                 error_counter += 1;
+            }
             parse_error
+        }
         for type_loop in &self.type_loops {
             let mut can_be_broken = false;
             debug_assert!(!type_loop.members.is_empty());
             for entry in &type_loop.members {
                 if entry.is_union {
                     let mono_type = self.mono_types[entry.type_id.0 as usize].variant.as_union();
                     debug_assert!(!mono_type.variants.is_empty()); // otherwise it couldn't be part of the type loop
                     let has_stack_variant = mono_type.variants.iter().any(|variant| !variant.lives_on_heap);
                     if has_stack_variant {
                         can_be_broken = true;
                         break;
+                    }
+                }
+            }
             if !can_be_broken {
                 // Construct a type loop error
                 return Err(construct_type_loop_error(&self.mono_types, type_loop, modules, heap));
+            }
+        }
         // If here, then all type loops have been resolved and we can lay out
         // all of the members
         self.type_loops.clear();
         return Ok(());
+    }
     /// Checks if the specified type needs to be resolved (i.e. we need to push
     /// a breadcrumb), is already resolved (i.e. we can continue with the next
     /// member of the currently considered type) or is in the process of being
     /// resolved (i.e. we're in a type loop). Because of borrowing rules we
     /// don't do any modifications of internal types here. Hence: if we
     /// return `PushBreadcrumb` then call `handle_new_breadcrumb_for_type_loops`
     /// to take care of storing the appropriate types.
     fn check_member_for_type_loops(
         breadcrumbs: &[TypeLoopBreadcrumb], definition_map: &DefinitionMap, mono_type_map: &MonoTypeMap,
         mono_key: &mut MonoSearchKey, concrete_type: &ConcreteType
     ) -> TypeLoopResult {
         use ConcreteTypePart as CTP;
         // Depending on the type, lookup if the type has already been visited
         // (i.e. either already has its memory layed out, or is part of a type
         // loop because we've already visited the type)
         debug_assert!(!concrete_type.parts.is_empty());
         let definition_id = if let ConcreteTypePart::Instance(definition_id, _) = concrete_type.parts[0] {
             definition_id
         } else {
             DefinitionId::new_invalid()
         };
         Self::set_search_key_to_type(mono_key, definition_map, &concrete_type.parts);
         if let Some(type_id) = mono_type_map.get(mono_key).copied() {
             for (breadcrumb_idx, breadcrumb) in breadcrumbs.iter().enumerate() {
                 if breadcrumb.type_id == type_id {
                     return TypeLoopResult::TypeLoop(breadcrumb_idx);
+                }
+            }
             return TypeLoopResult::TypeExists;
+        }
         // Type is not yet known, so we need to insert it into the lookup and
         // push a new breadcrumb.
         return TypeLoopResult::PushBreadcrumb(definition_id, concrete_type.clone());
+    }
     /// Handles the `PushBreadcrumb` result for a `check_member_for_type_loops`
     /// call. Will preallocate entries in the monomorphed type storage (with
     /// all memory properties zeroed).
     fn handle_new_breadcrumb_for_type_loops(&mut self, arch: &TargetArch, definition_id: DefinitionId, concrete_type: ConcreteType) {
         use DefinedTypeVariant as DTV;
         use ConcreteTypePart as CTP;
         let mut is_union = false;
         let type_id = match &concrete_type.parts[0] {
             // Builtin types
             CTP::Void | CTP::Message | CTP::Bool |
             CTP::UInt8 | CTP::UInt16 | CTP::UInt32 | CTP::UInt64 |
             CTP::SInt8 | CTP::SInt16 | CTP::SInt32 | CTP::SInt64 |
             CTP::Character | CTP::String |
             CTP::Array | CTP::Slice | CTP::Input | CTP::Output | CTP::Pointer => {
                 // Insert the entry for the builtin type, we should be able to
                 // immediately "steal" the size from the preinserted builtins.
                 let base_type_id = match &concrete_type.parts[0] {
                     CTP::Void => arch.void_type_id,
                     CTP::Message => arch.message_type_id,
                     CTP::Bool => arch.bool_type_id,
                     CTP::UInt8 => arch.uint8_type_id,
                     CTP::UInt16 => arch.uint16_type_id,
                     CTP::UInt32 => arch.uint32_type_id,
                     CTP::UInt64 => arch.uint64_type_id,
                     CTP::SInt8 => arch.sint8_type_id,
                     CTP::SInt16 => arch.sint16_type_id,
                     CTP::SInt32 => arch.sint32_type_id,
                     CTP::SInt64 => arch.sint64_type_id,
                     CTP::Character => arch.char_type_id,
                     CTP::String => arch.string_type_id,
                     CTP::Array => arch.array_type_id,
                     CTP::Slice => arch.slice_type_id,
                     CTP::Input => arch.input_type_id,
                     CTP::Output => arch.output_type_id,
                     CTP::Pointer => arch.pointer_type_id,
                     _ => unreachable!(),
                 };
                 let base_type = &self.mono_types[base_type_id.0 as usize];
                 let type_id = TypeId(self.mono_types.len() as i64);
                 Self::set_search_key_to_type(&mut self.mono_search_key, &self.definition_lookup, &concrete_type.parts);
                 self.mono_type_lookup.insert(self.mono_search_key.clone(), type_id);
                 self.mono_types.push(MonoType{
                     type_id,
                     concrete_type,
                     size: base_type.size,
                     alignment: base_type.alignment,
                     variant: MonoTypeVariant::Builtin
                 });
                 type_id
             },
             // User-defined types
             CTP::Tuple(num_embedded) => {
                 debug_assert!(definition_id.is_invalid()); // because tuples do not have an associated `DefinitionId`
                 let mut members = Vec::with_capacity(*num_embedded as usize);
                 for section in ConcreteTypeIter::new(&concrete_type.parts, 0) {
                     members.push(TupleMonomorphMember{
                         type_id: TypeId::new_invalid(),
                         concrete_type: ConcreteType{ parts: Vec::from(section) },
                         size: 0,
                         alignment: 0,
                         offset: 0
                     });
+                }
                 let type_id = TypeId(self.mono_types.len() as i64);
                 Self::set_search_key_to_tuple(&mut self.mono_search_key, &self.definition_lookup, &concrete_type.parts);
                 self.mono_type_lookup.insert(self.mono_search_key.clone(), type_id);
                 self.mono_types.push(MonoType::new_empty(type_id, concrete_type, MonoTypeVariant::Tuple(TupleMonomorph{ members })));
                 type_id
             },
             CTP::Instance(_check_definition_id, _) => {
                 debug_assert_eq!(definition_id, *_check_definition_id); // because this is how `definition_id` was determined
                 Self::set_search_key_to_type(&mut self.mono_search_key, &self.definition_lookup, &concrete_type.parts);
                 let base_type = self.definition_lookup.get(&definition_id).unwrap();
                 let type_id = match &base_type.definition {
                     DTV::Enum(definition) => {
                         // The enum is a bit exceptional in that when we insert
                         // it we we will immediately set its size/alignment:
                         // there is nothing to compute here.
                         debug_assert!(definition.size != 0 && definition.alignment != 0);
                         let type_id = TypeId(self.mono_types.len() as i64);
                         self.mono_type_lookup.insert(self.mono_search_key.clone(), type_id);
                         self.mono_types.push(MonoType::new_empty(type_id, concrete_type, MonoTypeVariant::Enum));
                         let mono_type = &mut self.mono_types[type_id.0 as usize];
                         mono_type.size = definition.size;
                         mono_type.alignment = definition.alignment;
                         type_id
                     },
                     DTV::Union(definition) => {
                         // Create all the variants with their concrete types
                         let mut mono_variants = Vec::with_capacity(definition.variants.len());
                         for poly_variant in &definition.variants {
                             let mut mono_embedded = Vec::with_capacity(poly_variant.embedded.len());
                             for poly_embedded in &poly_variant.embedded {
                                 let mono_concrete = Self::construct_concrete_type(poly_embedded, &concrete_type);
                                 mono_embedded.push(UnionMonomorphEmbedded{
                                     type_id: TypeId::new_invalid(),
                                     concrete_type: mono_concrete,
                                     size: 0,
                                     alignment: 0,
                                     offset: 0
                                 });
+                            }
                             mono_variants.push(UnionMonomorphVariant{
                                 lives_on_heap: false,
                                 embedded: mono_embedded,
                             })
+                        }
                         let type_id = TypeId(self.mono_types.len() as i64);
                         let tag_size = definition.tag_size;
                         Self::set_search_key_to_type(&mut self.mono_search_key, &self.definition_lookup, &concrete_type.parts);
                         self.mono_type_lookup.insert(self.mono_search_key.clone(), type_id);
                         self.mono_types.push(MonoType::new_empty(type_id, concrete_type, MonoTypeVariant::Union(UnionMonomorph{
                             variants: mono_variants,
                             tag_size,
                             heap_size: 0,
                             heap_alignment: 0,
                         })));
                         is_union = true;
                         type_id
                     },
                     DTV::Struct(definition) => {
                         // Create fields
                         let mut mono_fields = Vec::with_capacity(definition.fields.len());
                         for poly_field in &definition.fields {
                             let mono_concrete = Self::construct_concrete_type(&poly_field.parser_type, &concrete_type);
                             mono_fields.push(StructMonomorphField{
                                 type_id: TypeId::new_invalid(),
                                 concrete_type: mono_concrete,
                                 size: 0,
                                 alignment: 0,
                                 offset: 0
                             })
+                        }
                         let type_id = TypeId(self.mono_types.len() as i64);
                         Self::set_search_key_to_type(&mut self.mono_search_key, &self.definition_lookup, &concrete_type.parts);
                         self.mono_type_lookup.insert(self.mono_search_key.clone(), type_id);
                         self.mono_types.push(MonoType::new_empty(type_id, concrete_type, MonoTypeVariant::Struct(StructMonomorph{
                             fields: mono_fields,
                         })));
                         type_id
                     },
                     DTV::Procedure(_) => {
                         unreachable!("pushing type resolving breadcrumb for procedure type")
                     },
                 };
                 type_id
             },
             CTP::Function(_, _) | CTP::Component(_, _) => todo!("function pointers"),
         };
         self.encountered_types.push(TypeLoopEntry{ type_id, is_union });
         self.type_loop_breadcrumbs.push(TypeLoopBreadcrumb{
             type_id,
             next_member: 0,
             next_embedded: 0,
         });
+    }
     /// Constructs a concrete type out of a parser type for a struct field or
     /// union embedded type. It will do this by looking up the polymorphic
     /// variables in the supplied concrete type. The assumption is that the
     /// polymorphic variable's indices correspond to the subtrees in the
     /// concrete type.
     fn construct_concrete_type(member_type: &ParserType, container_type: &ConcreteType) -> ConcreteType {
         use ParserTypeVariant as PTV;
         use ConcreteTypePart as CTP;
         // TODO: Combine with code in pass_typing.rs
         fn parser_to_concrete_part(part: &ParserTypeVariant) -> Option<ConcreteTypePart> {
             match part {
                 PTV::Void      => Some(CTP::Void),
                 PTV::Message   => Some(CTP::Message),
                 PTV::Bool      => Some(CTP::Bool),
                 PTV::UInt8     => Some(CTP::UInt8),
                 PTV::UInt16    => Some(CTP::UInt16),
                 PTV::UInt32    => Some(CTP::UInt32),
                 PTV::UInt64    => Some(CTP::UInt64),
                 PTV::SInt8     => Some(CTP::SInt8),
                 PTV::SInt16    => Some(CTP::SInt16),
                 PTV::SInt32    => Some(CTP::SInt32),
                 PTV::SInt64    => Some(CTP::SInt64),
                 PTV::Character => Some(CTP::Character),
                 PTV::String    => Some(CTP::String),
                 PTV::Array     => Some(CTP::Array),
                 PTV::Input     => Some(CTP::Input),
                 PTV::Output    => Some(CTP::Output),
                 PTV::Tuple(num) => Some(CTP::Tuple(*num)),
                 PTV::Definition(definition_id, num) => Some(CTP::Instance(*definition_id, *num)),
                 _              => None
+            }
+        }
         let mut parts = Vec::with_capacity(member_type.elements.len()); // usually a correct estimation, might not be
         for member_part in &member_type.elements {
             // Check if we have a regular builtin type
             if let Some(part) = parser_to_concrete_part(&member_part.variant) {
                 parts.push(part);
                 continue;
+            }
             // Not builtin, but if all code is working correctly, we only care
             // about the polymorphic argument at this point.
             if let PTV::PolymorphicArgument(_container_definition_id, poly_arg_idx) = member_part.variant {
                 debug_assert_eq!(_container_definition_id, get_concrete_type_definition(&container_type.parts).unwrap());
                 let mut container_iter = container_type.embedded_iter(0);
                 for _ in 0..poly_arg_idx {
                     container_iter.next();
+                }
                 let poly_section = container_iter.next().unwrap();
                 parts.extend(poly_section);
                 continue;
+            }
             unreachable!("unexpected type part {:?} from {:?}", member_part, member_type);
+        }
         return ConcreteType{ parts };
+    }
     //--------------------------------------------------------------------------
     // Determining memory layout for types
     //--------------------------------------------------------------------------
     /// Should be called after type loops are detected (and resolved
     /// successfully). As a result of this call we expect the
     /// `encountered_types` array to be filled. We'll calculate size/alignment/
     /// offset values for those types in this routine.
     fn lay_out_memory_for_encountered_types(&mut self, arch: &TargetArch) {
         // Programmers note: this works like a little stack machine. We have
         // memory layout breadcrumbs which, like the type loop breadcrumbs, keep
         // track of the currently considered member type. This breadcrumb also
         // stores an index into the `size_alignment_stack`, which will be used
         // to store intermediate size/alignment pairs until all members are
         // resolved. Note that this `size_alignment_stack` is NOT an
         // optimization, we're working around borrowing rules here.
         // Just finished type loop detection, so we're left with the encountered
         // types only. If we don't have any (a builtin type's monomorph was
         // added to the type table) then this function shouldn't be called at
         // all.
         debug_assert!(self.type_loops.is_empty());
         debug_assert!(!self.encountered_types.is_empty());
         debug_assert!(self.memory_layout_breadcrumbs.is_empty());
         debug_assert!(self.size_alignment_stack.is_empty());
         let (ptr_size, ptr_align) = self.mono_types[arch.pointer_type_id.0 as usize].get_size_alignment().unwrap();
         // Push the first entry (the type we originally started with when we
         // were detecting type loops)
         let first_entry = &self.encountered_types[0];
         self.memory_layout_breadcrumbs.push(MemoryBreadcrumb{
             type_id: first_entry.type_id,
             next_member: 0,
             next_embedded: 0,
             first_size_alignment_idx: 0,
         });
         // Enter the main resolving loop
         'breadcrumb_loop: while !self.memory_layout_breadcrumbs.is_empty() {
             let cur_breadcrumb_idx = self.memory_layout_breadcrumbs.len() - 1;
             let mut breadcrumb = self.memory_layout_breadcrumbs[cur_breadcrumb_idx].clone();
             let mono_type = &self.mono_types[breadcrumb.type_id.0 as usize];
             match &mono_type.variant {
                 MonoTypeVariant::Builtin | MonoTypeVariant::Enum => {
                     // Size should already be computed
                     dbg_code!({
                         let mono_type = &self.mono_types[breadcrumb.type_id.0 as usize];
                         debug_assert!(mono_type.size != 0 && mono_type.alignment != 0);
                     });
                 },
                 MonoTypeVariant::Union(mono_type) => {
                     // Retrieve size/alignment of each embedded type. We do not
                     // compute the offsets or total type sizes yet.
                     let num_variants = mono_type.variants.len() as u32;
                     while breadcrumb.next_member < num_variants {
                         let mono_variant = &mono_type.variants[breadcrumb.next_member as usize];
                         if mono_variant.lives_on_heap {
                             // To prevent type loops we made this a heap-
                             // allocated variant. This implies we cannot
                             // compute sizes of members at this point.
                         } else {
                             let num_embedded = mono_variant.embedded.len() as u32;
                             while breadcrumb.next_embedded < num_embedded {
                                 let mono_embedded = &mono_variant.embedded[breadcrumb.next_embedded as usize];
                                 let layout_result = Self::get_memory_layout_or_breadcrumb(
                                     &self.definition_lookup, &self.mono_type_lookup, &self.mono_types,
                                     &mut self.mono_search_key, arch, &mono_embedded.concrete_type.parts,
                                     self.size_alignment_stack.len()
                                 );
                                 match layout_result {
                                     MemoryLayoutResult::TypeExists(size, alignment) => {
                                         self.size_alignment_stack.push((size, alignment));
                                     },
                                     MemoryLayoutResult::PushBreadcrumb(new_breadcrumb) => {
                                         self.memory_layout_breadcrumbs[cur_breadcrumb_idx] = breadcrumb;
                                         self.memory_layout_breadcrumbs.push(new_breadcrumb);
                                         continue 'breadcrumb_loop;
+                                    }
+                                }
                                 breadcrumb.next_embedded += 1;
+                            }
+                        }
                         breadcrumb.next_member += 1;
                         breadcrumb.next_embedded = 0;
+                    }
                     // If here then we can at least compute the stack size of
                     // the type, we'll have to come back at the very end to
                     // fill in the heap size/alignment/offset of each heap-
                     // allocated variant.
                     let mut max_size = mono_type.tag_size;
                     let mut max_alignment = mono_type.tag_size;
                     let mono_type = &mut self.mono_types[breadcrumb.type_id.0 as usize];
                     let union_type = mono_type.variant.as_union_mut();
                     let mut size_alignment_idx = breadcrumb.first_size_alignment_idx as usize;
                     for variant in &mut union_type.variants {
                         // We're doing stack computations, so always start with
                         // the tag size/alignment.
                         let mut variant_offset = union_type.tag_size;
                         let mut variant_alignment = union_type.tag_size;
                         if variant.lives_on_heap {
                             // Variant lives on heap, so just a pointer
                             align_offset_to(&mut variant_offset, ptr_align);
                             variant_offset += ptr_size;
                             variant_alignment = variant_alignment.max(ptr_align);
                         } else {
                             // Variant lives on stack, so walk all embedded
                             // types.
                             for embedded in &mut variant.embedded {
                                 let (size, alignment) = self.size_alignment_stack[size_alignment_idx];
                                 embedded.size = size;
                                 embedded.alignment = alignment;
                                 size_alignment_idx += 1;
                                 align_offset_to(&mut variant_offset, alignment);
                                 embedded.offset = variant_offset;
                                 variant_offset += size;
                                 variant_alignment = variant_alignment.max(alignment);
+                            }
                         };
                         max_size = max_size.max(variant_offset);
                         max_alignment = max_alignment.max(variant_alignment);
+                    }
                     mono_type.size = max_size;
                     mono_type.alignment = max_alignment;
                     self.size_alignment_stack.truncate(breadcrumb.first_size_alignment_idx as usize);
                 },
                 MonoTypeVariant::Struct(mono_type) => {
                     // Retrieve size and alignment of each struct member. We'll
                     // compute the offsets once all of those are known
                     let num_fields = mono_type.fields.len() as u32;
                     while breadcrumb.next_member < num_fields {
                         let mono_field = &mono_type.fields[breadcrumb.next_member as usize];
                         let layout_result = Self::get_memory_layout_or_breadcrumb(
                             &self.definition_lookup, &self.mono_type_lookup, &self.mono_types,
                             &mut self.mono_search_key, arch, &mono_field.concrete_type.parts,
                             self.size_alignment_stack.len()
                         );
                         match layout_result {
                             MemoryLayoutResult::TypeExists(size, alignment) => {
                                 self.size_alignment_stack.push((size, alignment))
                             },
                             MemoryLayoutResult::PushBreadcrumb(new_breadcrumb) => {
                                 self.memory_layout_breadcrumbs[cur_breadcrumb_idx] = breadcrumb;
                                 self.memory_layout_breadcrumbs.push(new_breadcrumb);
                                 continue 'breadcrumb_loop;
                             },
+                        }
                         breadcrumb.next_member += 1;
+                    }
                     // Compute offsets and size of total type
                     let mut cur_offset = 0;
                     let mut max_alignment = 1;
                     let mono_type = &mut self.mono_types[breadcrumb.type_id.0 as usize];
                     let struct_type = mono_type.variant.as_struct_mut();
                     let mut size_alignment_idx = breadcrumb.first_size_alignment_idx as usize;
                     for field in &mut struct_type.fields {
                         let (size, alignment) = self.size_alignment_stack[size_alignment_idx];
                         field.size = size;
                         field.alignment = alignment;
                         size_alignment_idx += 1;
                         align_offset_to(&mut cur_offset, alignment);
                         field.offset = cur_offset;
                         cur_offset += size;
                         max_alignment = max_alignment.max(alignment);
+                    }
                     mono_type.size = cur_offset;
                     mono_type.alignment = max_alignment;
                     self.size_alignment_stack.truncate(breadcrumb.first_size_alignment_idx as usize);
                 },
                 MonoTypeVariant::Procedure(_) => {
                     unreachable!();
                 },
                 MonoTypeVariant::Tuple(mono_type) => {
                     let num_members = mono_type.members.len() as u32;
                     while breadcrumb.next_member < num_members {
                         let mono_member = &mono_type.members[breadcrumb.next_member as usize];
                         let layout_result = Self::get_memory_layout_or_breadcrumb(
                             &self.definition_lookup, &self.mono_type_lookup, &self.mono_types,
                             &mut self.mono_search_key, arch, &mono_member.concrete_type.parts,
                             self.size_alignment_stack.len()
                         );
                         match layout_result {
                             MemoryLayoutResult::TypeExists(size, alignment) => {
                                 self.size_alignment_stack.push((size, alignment));
                             },
                             MemoryLayoutResult::PushBreadcrumb(new_breadcrumb) => {
                                 self.memory_layout_breadcrumbs[cur_breadcrumb_idx] = breadcrumb;
                                 self.memory_layout_breadcrumbs.push(new_breadcrumb);
                                 continue 'breadcrumb_loop;
                             },
+                        }
                         breadcrumb.next_member += 1;
+                    }
                     // If here then we can compute the memory layout of the tuple.
                     let mut cur_offset = 0;
                     let mut max_alignment = 1;
                     let mono_type = &mut self.mono_types[breadcrumb.type_id.0 as usize];
                     let mono_tuple = mono_type.variant.as_tuple_mut();
                     let mut size_alignment_index = breadcrumb.first_size_alignment_idx as usize;
                     for member_index in 0..num_members {
                         let (member_size, member_alignment) = self.size_alignment_stack[size_alignment_index];
                         align_offset_to(&mut cur_offset, member_alignment);
                         size_alignment_index += 1;
                         let member = &mut mono_tuple.members[member_index as usize];
                         member.size = member_size;
                         member.alignment = member_alignment;
                         member.offset = cur_offset;
                         cur_offset += member_size;
                         max_alignment = max_alignment.max(member_alignment);
+                    }
                     mono_type.size = cur_offset;
                     mono_type.alignment = max_alignment;
                     self.size_alignment_stack.truncate(breadcrumb.first_size_alignment_idx as usize);
                 },
+            }
             // If here, then we completely layed out the current type. So move
             // to the next breadcrumb
             self.memory_layout_breadcrumbs.pop();
+        }
         debug_assert!(self.size_alignment_stack.is_empty());
         // If here then all types have been layed out. What remains is to
         // compute the sizes/alignment/offsets of the heap variants of the
         // unions we have encountered.
         for entry in &self.encountered_types {
             if !entry.is_union {
                 continue;
+            }
             // First pass, use buffer to store size/alignment to prevent
             // borrowing issues.
             let mono_type = self.mono_types[entry.type_id.0 as usize].variant.as_union();
             for variant in &mono_type.variants {
                 if !variant.lives_on_heap {
                     continue;
+                }
                 debug_assert!(!variant.embedded.is_empty());
                 for embedded in &variant.embedded {
                     let layout_result = Self::get_memory_layout_or_breadcrumb(
                         &self.definition_lookup, &self.mono_type_lookup, &self.mono_types,
                         &mut self.mono_search_key, arch, &embedded.concrete_type.parts,
                         self.size_alignment_stack.len()
                     );
                     match layout_result {
                         MemoryLayoutResult::TypeExists(size, alignment) => {
                             self.size_alignment_stack.push((size, alignment));
                         },
                         _ => unreachable!(), // type was not truly infinite, so type must have been found
+                    }
+                }
+            }
             // Second pass, apply the size/alignment values in our buffer
             let mono_type = self.mono_types[entry.type_id.0 as usize].variant.as_union_mut();
             let mut max_size = 0;
             let mut max_alignment = 1;
             let mut size_alignment_idx = 0;
             for variant in &mut mono_type.variants {
                 if !variant.lives_on_heap {
                     continue;
+                }

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