Changeset - 448252a297bd
[Not reviewed]
0 1 0
mh - 3 years ago 2022-02-15 10:30:25
contact@maxhenger.nl
Add initial procedure for builtin types in type table
1 file changed with 24 insertions and 1 deletions:
0 comments (0 inline, 0 general)
src/protocol/parser/type_table.rs
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@@ -44,384 +44,385 @@ use crate::protocol::ast::*;
 
use crate::protocol::parser::symbol_table::SymbolScope;
 
use crate::protocol::input_source::ParseError;
 
use crate::protocol::parser::*;
 

	
 
//------------------------------------------------------------------------------
 
// Defined Types
 
//------------------------------------------------------------------------------
 

	
 
#[derive(Copy, Clone, PartialEq, Eq)]
 
pub enum TypeClass {
 
    Enum,
 
    Union,
 
    Struct,
 
    Function,
 
    Component
 
}
 

	
 
impl TypeClass {
 
    pub(crate) fn display_name(&self) -> &'static str {
 
        match self {
 
            TypeClass::Enum => "enum",
 
            TypeClass::Union => "union",
 
            TypeClass::Struct => "struct",
 
            TypeClass::Function => "function",
 
            TypeClass::Component => "component",
 
        }
 
    }
 

	
 
    pub(crate) fn is_data_type(&self) -> bool {
 
        match self {
 
            TypeClass::Enum | TypeClass::Union | TypeClass::Struct => true,
 
            TypeClass::Function | TypeClass::Component => false,
 
        }
 
    }
 
}
 

	
 
impl std::fmt::Display for TypeClass {
 
    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
 
        write!(f, "{}", self.display_name())
 
    }
 
}
 

	
 
/// 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),
 
    Function(FunctionType),
 
    Component(ComponentType)
 
}
 

	
 
impl DefinedTypeVariant {
 
    pub(crate) fn type_class(&self) -> TypeClass {
 
        match self {
 
            DefinedTypeVariant::Enum(_) => TypeClass::Enum,
 
            DefinedTypeVariant::Union(_) => TypeClass::Union,
 
            DefinedTypeVariant::Struct(_) => TypeClass::Struct,
 
            DefinedTypeVariant::Function(_) => TypeClass::Function,
 
            DefinedTypeVariant::Component(_) => TypeClass::Component
 
        }
 
    }
 

	
 
    pub(crate) fn as_struct(&self) -> &StructType {
 
        match self {
 
            DefinedTypeVariant::Struct(v) => v,
 
            _ => unreachable!("Cannot convert {} to struct variant", self.type_class())
 
        }
 
    }
 

	
 
    pub(crate) fn as_enum(&self) -> &EnumType {
 
        match self {
 
            DefinedTypeVariant::Enum(v) => v,
 
            _ => unreachable!("Cannot convert {} to enum variant", self.type_class())
 
        }
 
    }
 

	
 
    pub(crate) fn as_union(&self) -> &UnionType {
 
        match self {
 
            DefinedTypeVariant::Union(v) => v,
 
            _ => unreachable!("Cannot convert {} to union variant", self.type_class())
 
        }
 
    }
 
}
 

	
 
pub struct PolymorphicVariable {
 
    identifier: Identifier,
 
    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,
 
}
 

	
 
/// `FunctionType` is what you expect it to be: a particular function's
 
/// signature.
 
pub struct FunctionType {
 
    pub return_type: ParserType,
 
    pub arguments: Vec<FunctionArgument>,
 
}
 

	
 
pub struct ComponentType {
 
    pub variant: ComponentVariant,
 
    pub arguments: Vec<FunctionArgument>,
 
}
 

	
 
pub struct FunctionArgument {
 
    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!(),
 
        }
 
    }
 

	
 
    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 {
 
    // Expression data for one particular monomorph
 
    pub arg_types: Vec<ConcreteType>,
 
    pub expr_data: Vec<MonomorphExpression>,
 
}
 

	
 
/// 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;
 
@@ -585,384 +586,403 @@ struct MemoryBreadcrumb {
 
#[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::Function(_) => self.build_base_function_definition(modules, ctx, definition_id)?,
 
                Definition::Component(_) => self.build_base_component_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.type_class().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,
 
                    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.
 
        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];
 
    }
 

	
 
    /// Returns a mutable reference to a procedure's monomorph expression data.
 
    /// Used by typechecker to fill in previously reserved type information
 
    #[inline]
 
    pub(crate) fn get_procedure_monomorph_mut(&mut self, type_id: TypeId) -> &mut ProcedureMonomorph {
 
        let mono_type = &mut self.mono_types[type_id.0 as usize];
 
        return mono_type.variant.as_procedure_mut();
 
    }
 

	
 
    #[inline]
 
    pub(crate) fn get_procedure_monomorph(&self, type_id: TypeId) -> &ProcedureMonomorph {
 
        let mono_type = &self.mono_types[type_id.0 as usize];
 
        return mono_type.variant.as_procedure();
 
    }
 

	
 
    /// 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) -> TypeId {
 
        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{
 
            arg_types: Vec::new(),
 
            expr_data: Vec::new(),
 
        })));
 

	
 
        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.
 
    // TODO: Finish this train of thought, requires a little bit of design work
 
    pub(crate) fn add_builtin_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));
 
        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 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,
 
        definition_id: DefinitionId, concrete_type: ConcreteType
 
    ) -> Result<TypeId, ParseError> {
 
        debug_assert_eq!(definition_id, get_concrete_type_definition(&concrete_type.parts).unwrap());
 

	
 
        // Check if the concrete type was already added
 
        let definition = self.definition_lookup.get(&definition_id).unwrap();
 
        let poly_var_in_use = &definition.poly_vars;
 
        self.mono_search_key.set(&concrete_type.parts, poly_var_in_use.as_slice());
 
        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, 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);
 

	
 
@@ -1056,384 +1076,387 @@ impl TypeTable {
 
        Self::check_poly_args_collision(modules, ctx, root_id, &definition.poly_vars)?;
 

	
 
        // Construct internal representation of component
 
        // TODO: Marking used polymorphic variables on procedures requires
 
        //  making sure that each is used in the body. For now, mark them all
 
        //  as required.
 
        let mut poly_vars = Self::create_polymorphic_variables(&definition.poly_vars);
 
        // for argument in &arguments {
 
        //     Self::mark_used_polymorphic_variables(&mut poly_vars, &argument.parser_type);
 
        // }
 
        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::Component(ComponentType{ variant: definition.variant, arguments }),
 
            poly_vars,
 
            is_polymorph
 
        });
 

	
 
        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, 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(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(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);
 
@@ -1597,385 +1620,385 @@ impl TypeTable {
 
                        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::Function(_) | DTV::Component(_) => {
 
                        unreachable!("pushing type resolving breadcrumb for procedure type")
 
                    },
 
                };
 

	
 
                type_id
 
            },
 
            _ => unreachable!(),
 
        };
 

	
 
        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
 
        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());
 

	
 
        // 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::Enum => {
 
                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
 
                            let (ptr_size, ptr_align) = arch.pointer_size_alignment;
 
                            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);
 
                    }
 

	
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