CSY/reowolf Changeset - 8ab54a37f6db · Centrum Wiskunde & Informatica (CWI)

Changeset - 8ab54a37f6db

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MH - 4 years ago 2021-04-06 19:08:32
henger@cwi.nl

Initial bugfixing for unions

2 files changed:

src/protocol/parser/type_resolver.rs

src/protocol/parser/type_table.rs

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src/protocol/parser/type_resolver.rs

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@@ @@ -661,1536 +661,1537 @@ impl InferenceType { @@
                 idx = Self::write_display_name(buffer, heap, parts, idx + 1);
             },
             ITP::Unknown => buffer.push_str("?"),
             ITP::NumberLike => buffer.push_str("num?"),
             ITP::IntegerLike => buffer.push_str("int?"),
             ITP::ArrayLike => {
                 idx = Self::write_display_name(buffer, heap, parts, idx + 1);
                 buffer.push_str("[?]");
             },
             ITP::PortLike => {
                 buffer.push_str("port?<");
                 idx = Self::write_display_name(buffer, heap, parts, idx + 1);
                 buffer.push('>');
+            }
             ITP::Void => buffer.push_str("void"),
             ITP::Bool => buffer.push_str("bool"),
             ITP::Byte => buffer.push_str("byte"),
             ITP::Short => buffer.push_str("short"),
             ITP::Int => buffer.push_str("int"),
             ITP::Long => buffer.push_str("long"),
             ITP::String => buffer.push_str("str"),
             ITP::Message => {
                 buffer.push_str("msg<");
                 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("in<");
                 idx = Self::write_display_name(buffer, heap, parts, idx + 1);
                 buffer.push('>');
             },
             ITP::Output => {
                 buffer.push_str("out<");
                 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(&String::from_utf8_lossy(&definition.identifier().value));
                 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)
+    }
+}
 /// 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 = (usize, &'a [InferenceTypePart]);
     fn next(&mut self) -> Option<Self::Item> {
         // Iterate until we find a marker
         while self.idx < self.parts.len() {
             if let InferenceTypePart::MarkerBody(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
+}
 enum DefinitionType{
     None, // Token value, never used during actual inference
     Component(ComponentId),
     Function(FunctionId),
+}
 #[derive(PartialEq, Eq)]
 pub(crate) struct ResolveQueueElement {
     pub(crate) root_id: RootId,
     pub(crate) definition_id: DefinitionId,
     pub(crate) monomorph_types: Vec<ConcreteType>,
+}
 pub(crate) type ResolveQueue = Vec<ResolveQueueElement>;
 /// This particular visitor will recurse depth-first into the AST and ensures
 /// that all expressions have the appropriate types.
 pub(crate) struct TypeResolvingVisitor {
     // Current definition we're typechecking.
     definition_type: DefinitionType,
     poly_vars: Vec<ConcreteType>,
     // Buffers for iteration over substatements and subexpressions
     stmt_buffer: Vec<StatementId>,
     expr_buffer: Vec<ExpressionId>,
     // 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.
     var_types: HashMap<VariableId, VarData>,      // types of variables
     expr_types: HashMap<ExpressionId, InferenceType>,   // types of expressions
     extra_data: HashMap<ExpressionId, ExtraData>,       // data for polymorph inference
     // Keeping track of which expressions need to be reinferred because the
     // expressions they're linked to made progression on an associated type
     expr_queued: HashSet<ExpressionId>,
+}
 // TODO: @rename used for calls and struct literals, maybe union literals?
 struct ExtraData {
     /// Progression of polymorphic variables (if any)
     poly_vars: Vec<InferenceType>,
     /// Progression of types of call arguments or struct members
     embedded: Vec<InferenceType>,
     returned: InferenceType,
+}
 struct VarData {
     /// Type of the variable
     var_type: InferenceType,
     /// VariableExpressions that use the variable
     used_at: Vec<ExpressionId>,
     /// For channel statements we link to the other variable such that when one
     /// channel's interior type is resolved, we can also resolve the other one.
     linked_var: Option<VariableId>,
+}
 impl VarData {
     fn new_channel(var_type: InferenceType, other_port: VariableId) -> Self {
         Self{ var_type, used_at: Vec::new(), linked_var: Some(other_port) }
+    }
     fn new_local(var_type: InferenceType) -> Self {
         Self{ var_type, used_at: Vec::new(), linked_var: None }
+    }
+}
 impl TypeResolvingVisitor {
     pub(crate) fn new() -> Self {
         TypeResolvingVisitor{
             definition_type: DefinitionType::None,
             poly_vars: Vec::new(),
             stmt_buffer: Vec::with_capacity(STMT_BUFFER_INIT_CAPACITY),
             expr_buffer: Vec::with_capacity(EXPR_BUFFER_INIT_CAPACITY),
             var_types: HashMap::new(),
             expr_types: HashMap::new(),
             extra_data: HashMap::new(),
             expr_queued: HashSet::new(),
+        }
+    }
     // TODO: @cleanup Unsure about this, maybe a pattern will arise after
     //  a while.
     pub(crate) fn queue_module_definitions(ctx: &Ctx, queue: &mut ResolveQueue) {
         let root_id = ctx.module.root_id;
         let root = &ctx.heap.protocol_descriptions[root_id];
         for definition_id in &root.definitions {
             let definition = &ctx.heap[*definition_id];
             match definition {
                 Definition::Function(definition) => {
                     if definition.poly_vars.is_empty() {
                         queue.push(ResolveQueueElement{
                             root_id,
                             definition_id: *definition_id,
                             monomorph_types: Vec::new(),
                         })
+                    }
                 },
                 Definition::Component(definition) => {
                     if definition.poly_vars.is_empty() {
                         queue.push(ResolveQueueElement{
                             root_id,
                             definition_id: *definition_id,
                             monomorph_types: Vec::new(),
                         })
+                    }
                 },
                 Definition::Enum(_) | Definition::Struct(_) | Definition::Union(_) => {},
+            }
+        }
+    }
     pub(crate) fn handle_module_definition(
         &mut self, ctx: &mut Ctx, queue: &mut ResolveQueue, element: ResolveQueueElement
     ) -> VisitorResult {
         // Visit the definition
         debug_assert_eq!(ctx.module.root_id, element.root_id);
         self.reset();
         self.poly_vars.clear();
         self.poly_vars.extend(element.monomorph_types.iter().cloned());
         self.visit_definition(ctx, element.definition_id)?;
         // Keep resolving types
         self.resolve_types(ctx, queue)?;
         Ok(())
+    }
     fn reset(&mut self) {
         self.definition_type = DefinitionType::None;
         self.poly_vars.clear();
         self.stmt_buffer.clear();
         self.expr_buffer.clear();
         self.var_types.clear();
         self.expr_types.clear();
         self.extra_data.clear();
         self.expr_queued.clear();
+    }
+}
 impl Visitor2 for TypeResolvingVisitor {
     // Definitions
     fn visit_component_definition(&mut self, ctx: &mut Ctx, id: ComponentId) -> VisitorResult {
         self.definition_type = DefinitionType::Component(id);
         let comp_def = &ctx.heap[id];
         debug_assert_eq!(comp_def.poly_vars.len(), self.poly_vars.len(), "component polyvars do not match imposed polyvars");
         debug_log!("{}", "-".repeat(50));
         debug_log!("Visiting component '{}': {}", &String::from_utf8_lossy(&comp_def.identifier.value), id.0.index);
         debug_log!("{}", "-".repeat(50));
         for param_id in comp_def.parameters.clone() {
             let param = &ctx.heap[param_id];
             let var_type = self.determine_inference_type_from_parser_type(ctx, param.parser_type, true);
             debug_assert!(var_type.is_done, "expected component arguments to be concrete types");
             self.var_types.insert(param_id.upcast(), VarData::new_local(var_type));
+        }
         let body_stmt_id = ctx.heap[id].body;
         self.visit_stmt(ctx, body_stmt_id)
+    }
     fn visit_function_definition(&mut self, ctx: &mut Ctx, id: FunctionId) -> VisitorResult {
         self.definition_type = DefinitionType::Function(id);
         let func_def = &ctx.heap[id];
         debug_assert_eq!(func_def.poly_vars.len(), self.poly_vars.len(), "function polyvars do not match imposed polyvars");
         debug_log!("{}", "-".repeat(50));
         debug_log!("Visiting function '{}': {}", &String::from_utf8_lossy(&func_def.identifier.value), id.0.index);
         debug_log!("{}", "-".repeat(50));
         for param_id in func_def.parameters.clone() {
             let param = &ctx.heap[param_id];
             let var_type = self.determine_inference_type_from_parser_type(ctx, param.parser_type, true);
             debug_assert!(var_type.is_done, "expected function arguments to be concrete types");
             self.var_types.insert(param_id.upcast(), VarData::new_local(var_type));
+        }
         let body_stmt_id = ctx.heap[id].body;
         self.visit_stmt(ctx, body_stmt_id)
+    }
     // Statements
     fn visit_block_stmt(&mut self, ctx: &mut Ctx, id: BlockStatementId) -> VisitorResult {
         // Transfer statements for traversal
         let block = &ctx.heap[id];
         for stmt_id in block.statements.clone() {
             self.visit_stmt(ctx, stmt_id)?;
+        }
         Ok(())
+    }
     fn visit_local_memory_stmt(&mut self, ctx: &mut Ctx, id: MemoryStatementId) -> VisitorResult {
         let memory_stmt = &ctx.heap[id];
         let local = &ctx.heap[memory_stmt.variable];
         let var_type = self.determine_inference_type_from_parser_type(ctx, local.parser_type, true);
         self.var_types.insert(memory_stmt.variable.upcast(), VarData::new_local(var_type));
         Ok(())
+    }
     fn visit_local_channel_stmt(&mut self, ctx: &mut Ctx, id: ChannelStatementId) -> VisitorResult {
         let channel_stmt = &ctx.heap[id];
         let from_local = &ctx.heap[channel_stmt.from];
         let from_var_type = self.determine_inference_type_from_parser_type(ctx, from_local.parser_type, true);
         self.var_types.insert(from_local.this.upcast(), VarData::new_channel(from_var_type, channel_stmt.to.upcast()));
         let to_local = &ctx.heap[channel_stmt.to];
         let to_var_type = self.determine_inference_type_from_parser_type(ctx, to_local.parser_type, true);
         self.var_types.insert(to_local.this.upcast(), VarData::new_channel(to_var_type, channel_stmt.from.upcast()));
         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_id = if_stmt.true_body;
         let false_body_id = if_stmt.false_body;
         let test_expr_id = if_stmt.test;
         self.visit_expr(ctx, test_expr_id)?;
         self.visit_stmt(ctx, true_body_id)?;
         self.visit_stmt(ctx, false_body_id)?;
         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_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_return_stmt(&mut self, ctx: &mut Ctx, id: ReturnStatementId) -> VisitorResult {
         let return_stmt = &ctx.heap[id];
         let expr_id = return_stmt.expression;
         self.visit_expr(ctx, expr_id)
+    }
     fn visit_assert_stmt(&mut self, ctx: &mut Ctx, id: AssertStatementId) -> VisitorResult {
         let assert_stmt = &ctx.heap[id];
         let test_expr_id = assert_stmt.expression;
         self.visit_expr(ctx, test_expr_id)
+    }
     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)
+    }
     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)
+    }
     // Expressions
     fn visit_assignment_expr(&mut self, ctx: &mut Ctx, id: AssignmentExpressionId) -> VisitorResult {
         let upcast_id = id.upcast();
         self.insert_initial_expr_inference_type(ctx, upcast_id)?;
         let assign_expr = &ctx.heap[id];
         let left_expr_id = assign_expr.left;
         let right_expr_id = assign_expr.right;
         self.visit_expr(ctx, left_expr_id)?;
         self.visit_expr(ctx, right_expr_id)?;
         self.progress_assignment_expr(ctx, id)
+    }
     fn visit_conditional_expr(&mut self, ctx: &mut Ctx, id: ConditionalExpressionId) -> VisitorResult {
         let upcast_id = id.upcast();
         self.insert_initial_expr_inference_type(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;
         self.expr_types.insert(test_expr_id, InferenceType::new(false, true, vec![InferenceTypePart::Bool]));
         self.visit_expr(ctx, test_expr_id)?;
         self.visit_expr(ctx, true_expr_id)?;
         self.visit_expr(ctx, false_expr_id)?;
         self.progress_conditional_expr(ctx, id)
+    }
     fn visit_binary_expr(&mut self, ctx: &mut Ctx, id: BinaryExpressionId) -> VisitorResult {
         let upcast_id = id.upcast();
         self.insert_initial_expr_inference_type(ctx, upcast_id)?;
         let binary_expr = &ctx.heap[id];
         let lhs_expr_id = binary_expr.left;
         let rhs_expr_id = binary_expr.right;
         self.visit_expr(ctx, lhs_expr_id)?;
         self.visit_expr(ctx, rhs_expr_id)?;
         self.progress_binary_expr(ctx, id)
+    }
     fn visit_unary_expr(&mut self, ctx: &mut Ctx, id: UnaryExpressionId) -> VisitorResult {
         let upcast_id = id.upcast();
         self.insert_initial_expr_inference_type(ctx, upcast_id)?;
         let unary_expr = &ctx.heap[id];
         let arg_expr_id = unary_expr.expression;
         self.visit_expr(ctx, arg_expr_id)?;
         self.progress_unary_expr(ctx, id)
+    }
     fn visit_indexing_expr(&mut self, ctx: &mut Ctx, id: IndexingExpressionId) -> VisitorResult {
         let upcast_id = id.upcast();
         self.insert_initial_expr_inference_type(ctx, upcast_id)?;
         let indexing_expr = &ctx.heap[id];
         let subject_expr_id = indexing_expr.subject;
         let index_expr_id = indexing_expr.index;
         self.visit_expr(ctx, subject_expr_id)?;
         self.visit_expr(ctx, index_expr_id)?;
         self.progress_indexing_expr(ctx, id)
+    }
     fn visit_slicing_expr(&mut self, ctx: &mut Ctx, id: SlicingExpressionId) -> VisitorResult {
         let upcast_id = id.upcast();
         self.insert_initial_expr_inference_type(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;
         self.visit_expr(ctx, subject_expr_id)?;
         self.visit_expr(ctx, from_expr_id)?;
         self.visit_expr(ctx, to_expr_id)?;
         self.progress_slicing_expr(ctx, id)
+    }
     fn visit_select_expr(&mut self, ctx: &mut Ctx, id: SelectExpressionId) -> VisitorResult {
         let upcast_id = id.upcast();
         self.insert_initial_expr_inference_type(ctx, upcast_id)?;
         let select_expr = &ctx.heap[id];
         let subject_expr_id = select_expr.subject;
         self.visit_expr(ctx, subject_expr_id)?;
         self.progress_select_expr(ctx, id)
+    }
     fn visit_array_expr(&mut self, ctx: &mut Ctx, id: ArrayExpressionId) -> VisitorResult {
         let upcast_id = id.upcast();
         self.insert_initial_expr_inference_type(ctx, upcast_id)?;
         let array_expr = &ctx.heap[id];
         // TODO: @performance
         for element_id in array_expr.elements.clone().into_iter() {
             self.visit_expr(ctx, element_id)?;
+        }
         self.progress_array_expr(ctx, id)
+    }
     fn visit_literal_expr(&mut self, ctx: &mut Ctx, id: LiteralExpressionId) -> VisitorResult {
         let upcast_id = id.upcast();
         self.insert_initial_expr_inference_type(ctx, upcast_id)?;
         let literal_expr = &ctx.heap[id];
         match &literal_expr.value {
             Literal::Null | Literal::False | Literal::True |
             Literal::Integer(_) | Literal::Character(_) => {
                 // No subexpressions
             },
             Literal::Struct(literal) => {
                 // TODO: @performance
                 let expr_ids: Vec<_> = literal.fields
                     .iter()
                     .map(|f| f.value)
                     .collect();
                 self.insert_initial_struct_polymorph_data(ctx, id);
                 for expr_id in expr_ids {
                     self.visit_expr(ctx, expr_id)?;
+                }
             },
             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
                 self.insert_initial_enum_polymorph_data(ctx, id);
             },
             Literal::Union(literal) => {
                 // May carry subexpressions and polymorphic arguments
                 // TODO: @performance
                 let expr_ids = literal.values.clone();
                 self.insert_initial_union_polymorph_data(ctx, id);
                 for expr_id in expr_ids {
                     self.visit_expr(ctx, expr_id)?;
+                }
+            }
+        }
         self.progress_literal_expr(ctx, id)
+    }
     fn visit_call_expr(&mut self, ctx: &mut Ctx, id: CallExpressionId) -> VisitorResult {
         let upcast_id = id.upcast();
         self.insert_initial_expr_inference_type(ctx, upcast_id)?;
         self.insert_initial_call_polymorph_data(ctx, id);
         // TODO: @performance
         let call_expr = &ctx.heap[id];
         for arg_expr_id in call_expr.arguments.clone() {
             self.visit_expr(ctx, arg_expr_id)?;
+        }
         self.progress_call_expr(ctx, id)
+    }
     fn visit_variable_expr(&mut self, ctx: &mut Ctx, id: VariableExpressionId) -> VisitorResult {
         let upcast_id = id.upcast();
         self.insert_initial_expr_inference_type(ctx, upcast_id)?;
         let var_expr = &ctx.heap[id];
         debug_assert!(var_expr.declaration.is_some());
         let var_data = self.var_types.get_mut(var_expr.declaration.as_ref().unwrap()).unwrap();
         var_data.used_at.push(upcast_id);
         self.progress_variable_expr(ctx, id)
+    }
+}
 macro_rules! debug_assert_expr_ids_unique_and_known {
     // Base case for a single expression ID
     ($resolver:ident, $id:ident) => {
         if cfg!(debug_assertions) {
             $resolver.expr_types.contains_key(&$id);
+        }
     };
     // Base case for two expression IDs
     ($resolver:ident, $id1:ident, $id2:ident) => {
         debug_assert_ne!($id1, $id2);
         debug_assert_expr_ids_unique_and_known!($resolver, $id1);
         debug_assert_expr_ids_unique_and_known!($resolver, $id2);
     };
     // Generic case
     ($resolver:ident, $id1:ident, $id2:ident, $($tail:ident),+) => {
         debug_assert_ne!($id1, $id2);
         debug_assert_expr_ids_unique_and_known!($resolver, $id1);
         debug_assert_expr_ids_unique_and_known!($resolver, $id2, $($tail),+);
     };
+}
 macro_rules! debug_assert_ptrs_distinct {
     // Base case
     ($ptr1:ident, $ptr2:ident) => {
         debug_assert!(!std::ptr::eq($ptr1, $ptr2));
     };
     // Generic case
     ($ptr1:ident, $ptr2:ident, $($tail:ident),+) => {
         debug_assert_ptrs_distinct!($ptr1, $ptr2);
         debug_assert_ptrs_distinct!($ptr2, $($tail),+);
     };
+}
 impl TypeResolvingVisitor {
     fn resolve_types(&mut self, ctx: &mut Ctx, queue: &mut ResolveQueue) -> Result<(), ParseError> {
         // Keep inferring until we can no longer make any progress
         while let Some(next_expr_id) = self.expr_queued.iter().next() {
             let next_expr_id = *next_expr_id;
             self.expr_queued.remove(&next_expr_id);
             self.progress_expr(ctx, next_expr_id)?;
+        }
         // We check if we have all the types we need. If we're typechecking a
         // polymorphic procedure more than once, then we have already annotated
         // the AST and have now performed typechecking for a different
         // monomorph. In that case we just need to perform typechecking, no need
         // to annotate the AST again.
         let definition_id = match &self.definition_type {
             DefinitionType::Component(id) => id.upcast(),
             DefinitionType::Function(id) => id.upcast(),
             _ => unreachable!(),
         };
         let already_checked = ctx.types.get_base_definition(&definition_id).unwrap().has_any_monomorph();
         for (expr_id, expr_type) in self.expr_types.iter_mut() {
             if !expr_type.is_done {
                 // Auto-infer numberlike/integerlike types to a regular int
                 if expr_type.parts.len() == 1 && expr_type.parts[0] == InferenceTypePart::IntegerLike {
                     expr_type.parts[0] = InferenceTypePart::Int;
                 } else {
                     let expr = &ctx.heap[*expr_id];
                     return Err(ParseError::new_error(
                         &ctx.module.source, expr.position(),
                         &format!(
                             "Could not fully infer the type of this expression (got '{}')",
                             expr_type.display_name(&ctx.heap)
+                        )
                     ))
+                }
+            }
             if !already_checked {
                 let concrete_type = ctx.heap[*expr_id].get_type_mut();
                 expr_type.write_concrete_type(concrete_type);
             } else {
                 if cfg!(debug_assertions) {
                     let mut concrete_type = ConcreteType::default();
                     expr_type.write_concrete_type(&mut concrete_type);
                     debug_assert_eq!(*ctx.heap[*expr_id].get_type(), concrete_type);
+                }
+            }
+        }
         // All types are fine
         ctx.types.add_monomorph(&definition_id, self.poly_vars.clone());
         // Check all things we need to monomorphize
         // TODO: Struct/enum/union monomorphization
         for (expr_id, extra_data) in self.extra_data.iter() {
             if extra_data.poly_vars.is_empty() { continue; }
             // Retrieve polymorph variable specification. Those of struct
             // literals and those of procedure calls need to be fully inferred.
             // The remaining ones (e.g. select expressions) allow partial
             // inference of types, as long as the accessed field's type is
             // fully inferred.
             let needs_full_inference = match &ctx.heap[*expr_id] {
                 Expression::Call(_) => true,
                 Expression::Literal(_) => true,
                 _ => false
             };
             if needs_full_inference {
                 let mut monomorph_types = Vec::with_capacity(extra_data.poly_vars.len());
                 for (poly_idx, poly_type) in extra_data.poly_vars.iter().enumerate() {
                     if !poly_type.is_done {
                         // TODO: Single clean function for function signatures and polyvars.
                         // TODO: Better error message
                         let expr = &ctx.heap[*expr_id];
                         return Err(ParseError::new_error(
                             &ctx.module.source, expr.position(),
                             &format!(
                                 "Could not fully infer the type of polymorphic variable {} of this expression (got '{}')",
                                 poly_idx, poly_type.display_name(&ctx.heap)
+                            )
                         ))
+                    }
                     let mut concrete_type = ConcreteType::default();
                     poly_type.write_concrete_type(&mut concrete_type);
                     monomorph_types.insert(poly_idx, concrete_type);
+                }
                 // Resolve to the appropriate expression and instantiate
                 // monomorphs.
                 match &ctx.heap[*expr_id] {
                     Expression::Call(call_expr) => {
                         // Add to type table if not yet typechecked
                         if let Method::Symbolic(symbolic) = &call_expr.method {
                             let definition_id = symbolic.definition.unwrap();
                             if !ctx.types.has_monomorph(&definition_id, &monomorph_types) {
                                 let root_id = ctx.types
                                     .get_base_definition(&definition_id)
                                     .unwrap()
                                     .ast_root;
                                 // Pre-emptively add the monomorph to the type table, but
                                 // we still need to perform typechecking on it
                                 // TODO: Unsure about this, performance wise
                                 let queue_element = ResolveQueueElement{
                                     root_id,
                                     definition_id,
                                     monomorph_types,
                                 };
                                 if !queue.contains(&queue_element) {
                                     queue.push(queue_element);
+                                }
+                            }
+                        }
                     },
                     Expression::Literal(lit_expr) => {
                         let definition_id = match &lit_expr.value {
                             Literal::Struct(literal) => literal.definition.as_ref().unwrap(),
                             Literal::Enum(literal) => literal.definition.as_ref().unwrap(),
                             Literal::Union(literal) => literal.definition.as_ref().unwrap(),
                             _ => unreachable!("post-inference monomorph for non-struct, non-enum literal")
                         };
                         if !ctx.types.has_monomorph(definition_id, &monomorph_types) {
                             ctx.types.add_monomorph(definition_id, monomorph_types);
+                        }
                     },
                     _ => unreachable!("needs fully inference, but not a struct literal or call expression")
+                }
             } // else: was just a helper structure...
+        }
         Ok(())
+    }
     fn progress_expr(&mut self, ctx: &mut Ctx, id: ExpressionId) -> Result<(), ParseError> {
         match &ctx.heap[id] {
             Expression::Assignment(expr) => {
                 let id = expr.this;
                 self.progress_assignment_expr(ctx, id)
             },
             Expression::Conditional(expr) => {
                 let id = expr.this;
                 self.progress_conditional_expr(ctx, id)
             },
             Expression::Binary(expr) => {
                 let id = expr.this;
                 self.progress_binary_expr(ctx, id)
             },
             Expression::Unary(expr) => {
                 let id = expr.this;
                 self.progress_unary_expr(ctx, id)
             },
             Expression::Indexing(expr) => {
                 let id = expr.this;
                 self.progress_indexing_expr(ctx, id)
             },
             Expression::Slicing(expr) => {
                 let id = expr.this;
                 self.progress_slicing_expr(ctx, id)
             },
             Expression::Select(expr) => {
                 let id = expr.this;
                 self.progress_select_expr(ctx, id)
             },
             Expression::Array(expr) => {
                 let id = expr.this;
                 self.progress_array_expr(ctx, id)
             },
             Expression::Literal(expr) => {
                 let id = expr.this;
                 self.progress_literal_expr(ctx, id)
             },
             Expression::Call(expr) => {
                 let id = expr.this;
                 self.progress_call_expr(ctx, id)
             },
             Expression::Variable(expr) => {
                 let id = expr.this;
                 self.progress_variable_expr(ctx, id)
+            }
+        }
+    }
     fn progress_assignment_expr(&mut self, ctx: &mut Ctx, id: AssignmentExpressionId) -> Result<(), ParseError> {
         use AssignmentOperator as AO;
         // TODO: Assignable check
         let upcast_id = id.upcast();
         let expr = &ctx.heap[id];
         let arg1_expr_id = expr.left;
         let arg2_expr_id = expr.right;
         debug_log!("Assignment expr '{:?}': {}", expr.operation, upcast_id.index);
         debug_log!(" * Before:");
         debug_log!("   - Arg1 type: {}", self.expr_types.get(&arg1_expr_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Arg2 type: {}", self.expr_types.get(&arg2_expr_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Expr type: {}", self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         let progress_base = match expr.operation {
             AO::Set =>
                 false,
             AO::Multiplied | AO::Divided | AO::Added | AO::Subtracted =>
                 self.apply_forced_constraint(ctx, upcast_id, &NUMBERLIKE_TEMPLATE)?,
             AO::Remained | AO::ShiftedLeft | AO::ShiftedRight |
             AO::BitwiseAnded | AO::BitwiseXored | AO::BitwiseOred =>
                 self.apply_forced_constraint(ctx, upcast_id, &INTEGERLIKE_TEMPLATE)?,
         };
         let (progress_expr, progress_arg1, progress_arg2) = self.apply_equal3_constraint(
             ctx, upcast_id, arg1_expr_id, arg2_expr_id, 0
         )?;
         debug_log!(" * After:");
         debug_log!("   - Arg1 type [{}]: {}", progress_arg1, self.expr_types.get(&arg1_expr_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Arg2 type [{}]: {}", progress_arg2, self.expr_types.get(&arg2_expr_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Expr type [{}]: {}", progress_base || progress_expr, self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         if progress_base || progress_expr { self.queue_expr_parent(ctx, upcast_id); }
         if progress_arg1 { self.queue_expr(arg1_expr_id); }
         if progress_arg2 { self.queue_expr(arg2_expr_id); }
         Ok(())
+    }
     fn progress_conditional_expr(&mut self, ctx: &mut Ctx, id: ConditionalExpressionId) -> Result<(), ParseError> {
         // Note: test expression type is already enforced
         let upcast_id = id.upcast();
         let expr = &ctx.heap[id];
         let arg1_expr_id = expr.true_expression;
         let arg2_expr_id = expr.false_expression;
         debug_log!("Conditional expr: {}", upcast_id.index);
         debug_log!(" * Before:");
         debug_log!("   - Arg1 type: {}", self.expr_types.get(&arg1_expr_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Arg2 type: {}", self.expr_types.get(&arg2_expr_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Expr type: {}", self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         let (progress_expr, progress_arg1, progress_arg2) = self.apply_equal3_constraint(
             ctx, upcast_id, arg1_expr_id, arg2_expr_id, 0
         )?;
         debug_log!(" * After:");
         debug_log!("   - Arg1 type [{}]: {}", progress_arg1, self.expr_types.get(&arg1_expr_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Arg2 type [{}]: {}", progress_arg2, self.expr_types.get(&arg2_expr_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Expr type [{}]: {}", progress_expr, self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         if progress_expr { self.queue_expr_parent(ctx, upcast_id); }
         if progress_arg1 { self.queue_expr(arg1_expr_id); }
         if progress_arg2 { self.queue_expr(arg2_expr_id); }
         Ok(())
+    }
     fn progress_binary_expr(&mut self, ctx: &mut Ctx, id: BinaryExpressionId) -> Result<(), ParseError> {
         // Note: our expression type might be fixed by our parent, but we still
         // need to make sure it matches the type associated with our operation.
         use BinaryOperator as BO;
         let upcast_id = id.upcast();
         let expr = &ctx.heap[id];
         let arg1_id = expr.left;
         let arg2_id = expr.right;
         debug_log!("Binary expr '{:?}': {}", expr.operation, upcast_id.index);
         debug_log!(" * Before:");
         debug_log!("   - Arg1 type: {}", self.expr_types.get(&arg1_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Arg2 type: {}", self.expr_types.get(&arg2_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Expr type: {}", self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         let (progress_expr, progress_arg1, progress_arg2) = match expr.operation {
             BO::Concatenate => {
                 // Arguments may be arrays/slices, output is always an array
                 let progress_expr = self.apply_forced_constraint(ctx, upcast_id, &ARRAY_TEMPLATE)?;
                 let progress_arg1 = self.apply_forced_constraint(ctx, arg1_id, &ARRAYLIKE_TEMPLATE)?;
                 let progress_arg2 = self.apply_forced_constraint(ctx, arg2_id, &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, upcast_id, arg1_id, arg2_id, 1)?;
                 (progress_expr || subtype_expr, progress_arg1 || subtype_arg1, progress_arg2 || subtype_arg2)
             },
             BO::LogicalOr | BO::LogicalAnd => {
                 // Forced boolean on all
                 let progress_expr = self.apply_forced_constraint(ctx, upcast_id, &BOOL_TEMPLATE)?;
                 let progress_arg1 = self.apply_forced_constraint(ctx, arg1_id, &BOOL_TEMPLATE)?;
                 let progress_arg2 = self.apply_forced_constraint(ctx, arg2_id, &BOOL_TEMPLATE)?;
                 (progress_expr, progress_arg1, progress_arg2)
             },
             BO::BitwiseOr | BO::BitwiseXor | BO::BitwiseAnd | BO::Remainder | BO::ShiftLeft | BO::ShiftRight => {
                 // All equal of integer type
                 let progress_base = self.apply_forced_constraint(ctx, upcast_id, &INTEGERLIKE_TEMPLATE)?;
                 let (progress_expr, progress_arg1, progress_arg2) =
                     self.apply_equal3_constraint(ctx, upcast_id, arg1_id, arg2_id, 0)?;
                 (progress_base || progress_expr, progress_base || progress_arg1, progress_base || progress_arg2)
             },
             BO::Equality | BO::Inequality => {
                 // Equal2 on args, forced boolean output
                 let progress_expr = self.apply_forced_constraint(ctx, upcast_id, &BOOL_TEMPLATE)?;
                 let (progress_arg1, progress_arg2) =
                     self.apply_equal2_constraint(ctx, upcast_id, arg1_id, 0, arg2_id, 0)?;
                 (progress_expr, progress_arg1, progress_arg2)
             },
             BO::LessThan | BO::GreaterThan | BO::LessThanEqual | BO::GreaterThanEqual => {
                 // Equal2 on args with numberlike type, forced boolean output
                 let progress_expr = self.apply_forced_constraint(ctx, upcast_id, &BOOL_TEMPLATE)?;
                 let progress_arg_base = self.apply_forced_constraint(ctx, arg1_id, &NUMBERLIKE_TEMPLATE)?;
                 let (progress_arg1, progress_arg2) =
                     self.apply_equal2_constraint(ctx, upcast_id, arg1_id, 0, arg2_id, 0)?;
                 (progress_expr, progress_arg_base || progress_arg1, progress_arg_base || progress_arg2)
             },
             BO::Add | BO::Subtract | BO::Multiply | BO::Divide => {
                 // All equal of number type
                 let progress_base = self.apply_forced_constraint(ctx, upcast_id, &NUMBERLIKE_TEMPLATE)?;
                 let (progress_expr, progress_arg1, progress_arg2) =
                     self.apply_equal3_constraint(ctx, upcast_id, arg1_id, arg2_id, 0)?;
                 (progress_base || progress_expr, progress_base || progress_arg1, progress_base || progress_arg2)
             },
         };
         debug_log!(" * After:");
         debug_log!("   - Arg1 type [{}]: {}", progress_arg1, self.expr_types.get(&arg1_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Arg2 type [{}]: {}", progress_arg2, self.expr_types.get(&arg2_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Expr type [{}]: {}", progress_expr, self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         if progress_expr { self.queue_expr_parent(ctx, upcast_id); }
         if progress_arg1 { self.queue_expr(arg1_id); }
         if progress_arg2 { self.queue_expr(arg2_id); }
         Ok(())
+    }
     fn progress_unary_expr(&mut self, ctx: &mut Ctx, id: UnaryExpressionId) -> Result<(), ParseError> {
         use UnaryOperation as UO;
         let upcast_id = id.upcast();
         let expr = &ctx.heap[id];
         let arg_id = expr.expression;
         debug_log!("Unary expr '{:?}': {}", expr.operation, upcast_id.index);
         debug_log!(" * Before:");
         debug_log!("   - Arg  type: {}", self.expr_types.get(&arg_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Expr type: {}", self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         let (progress_expr, progress_arg) = match expr.operation {
             UO::Positive | UO::Negative => {
                 // Equal types of numeric class
                 let progress_base = self.apply_forced_constraint(ctx, upcast_id, &NUMBERLIKE_TEMPLATE)?;
                 let (progress_expr, progress_arg) =
                     self.apply_equal2_constraint(ctx, upcast_id, upcast_id, 0, arg_id, 0)?;
                 (progress_base || progress_expr, progress_base || progress_arg)
             },
             UO::BitwiseNot | UO::PreIncrement | UO::PreDecrement | UO::PostIncrement | UO::PostDecrement => {
                 // Equal types of integer class
                 let progress_base = self.apply_forced_constraint(ctx, upcast_id, &INTEGERLIKE_TEMPLATE)?;
                 let (progress_expr, progress_arg) =
                     self.apply_equal2_constraint(ctx, upcast_id, upcast_id, 0, arg_id, 0)?;
                 (progress_base || progress_expr, progress_base || progress_arg)
             },
             UO::LogicalNot => {
                 // Both booleans
                 let progress_expr = self.apply_forced_constraint(ctx, upcast_id, &BOOL_TEMPLATE)?;
                 let progress_arg = self.apply_forced_constraint(ctx, upcast_id, &BOOL_TEMPLATE)?;
                 (progress_expr, progress_arg)
+            }
         };
         debug_log!(" * After:");
         debug_log!("   - Arg  type [{}]: {}", progress_arg, self.expr_types.get(&arg_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Expr type [{}]: {}", progress_expr, self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         if progress_expr { self.queue_expr_parent(ctx, upcast_id); }
         if progress_arg { self.queue_expr(arg_id); }
         Ok(())
+    }
     fn progress_indexing_expr(&mut self, ctx: &mut Ctx, id: IndexingExpressionId) -> Result<(), ParseError> {
         let upcast_id = id.upcast();
         let expr = &ctx.heap[id];
         let subject_id = expr.subject;
         let index_id = expr.index;
         debug_log!("Indexing expr: {}", upcast_id.index);
         debug_log!(" * Before:");
         debug_log!("   - Subject type: {}", self.expr_types.get(&subject_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Index   type: {}", self.expr_types.get(&index_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Expr    type: {}", self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         // Make sure subject is arraylike and index is integerlike
         let progress_subject_base = self.apply_forced_constraint(ctx, subject_id, &ARRAYLIKE_TEMPLATE)?;
         let progress_index = self.apply_forced_constraint(ctx, index_id, &INTEGERLIKE_TEMPLATE)?;
         // Make sure if output is of T then subject is Array<T>
         let (progress_expr, progress_subject) =
             self.apply_equal2_constraint(ctx, upcast_id, upcast_id, 0, subject_id, 1)?;
         debug_log!(" * After:");
         debug_log!("   - Subject type [{}]: {}", progress_subject_base || progress_subject, self.expr_types.get(&subject_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Index   type [{}]: {}", progress_index, self.expr_types.get(&index_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Expr    type [{}]: {}", progress_expr, self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         if progress_expr { self.queue_expr_parent(ctx, upcast_id); }
         if progress_subject_base || progress_subject { self.queue_expr(subject_id); }
         if progress_index { self.queue_expr(index_id); }
         Ok(())
+    }
     fn progress_slicing_expr(&mut self, ctx: &mut Ctx, id: SlicingExpressionId) -> Result<(), ParseError> {
         let upcast_id = id.upcast();
         let expr = &ctx.heap[id];
         let subject_id = expr.subject;
         let from_id = expr.from_index;
         let to_id = expr.to_index;
         debug_log!("Slicing expr: {}", upcast_id.index);
         debug_log!(" * Before:");
         debug_log!("   - Subject type: {}", self.expr_types.get(&subject_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - FromIdx type: {}", self.expr_types.get(&from_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - ToIdx   type: {}", self.expr_types.get(&to_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Expr    type: {}", self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         // Make sure subject is arraylike and indices are of equal integerlike
         let progress_subject_base = self.apply_forced_constraint(ctx, subject_id, &ARRAYLIKE_TEMPLATE)?;
         let progress_idx_base = self.apply_forced_constraint(ctx, from_id, &INTEGERLIKE_TEMPLATE)?;
         let (progress_from, progress_to) = self.apply_equal2_constraint(ctx, upcast_id, from_id, 0, to_id, 0)?;
         // Make sure if output is of T then subject is Array<T>
         let (progress_expr, progress_subject) =
             self.apply_equal2_constraint(ctx, upcast_id, upcast_id, 0, subject_id, 1)?;
         debug_log!(" * After:");
         debug_log!("   - Subject type [{}]: {}", progress_subject_base || progress_subject, self.expr_types.get(&subject_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - FromIdx type [{}]: {}", progress_idx_base || progress_from, self.expr_types.get(&from_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - ToIdx   type [{}]: {}", progress_idx_base || progress_to, self.expr_types.get(&to_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Expr    type [{}]: {}", progress_expr, self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         if progress_expr { self.queue_expr_parent(ctx, upcast_id); }
         if progress_subject_base || progress_subject { self.queue_expr(subject_id); }
         if progress_idx_base || progress_from { self.queue_expr(from_id); }
         if progress_idx_base || progress_to { self.queue_expr(to_id); }
         Ok(())
+    }
     fn progress_select_expr(&mut self, ctx: &mut Ctx, id: SelectExpressionId) -> Result<(), ParseError> {
         let upcast_id = id.upcast();
         debug_log!("Select expr: {}", upcast_id.index);
         debug_log!(" * Before:");
         debug_log!("   - Subject type: {}", self.expr_types.get(&ctx.heap[id].subject).unwrap().display_name(&ctx.heap));
         debug_log!("   - Expr    type: {}", self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         let expr = &mut ctx.heap[id];
         let subject_id = expr.subject;
         fn determine_inference_type_instance<'a>(types: &'a TypeTable, infer_type: &InferenceType) -> Result<Option<&'a DefinedType>, ()> {
             for part in &infer_type.parts {
                 if part.is_marker() || !part.is_concrete() {
                     continue;
+                }
                 // Part is concrete, check if it is an instance of something
                 if let InferenceTypePart::Instance(definition_id, _num_sub) = part {
                     // Lookup type definition and ensure the specified field
                     // name exists on the struct
                     let definition = types.get_base_definition(definition_id);
                     debug_assert!(definition.is_some());
                     let definition = definition.unwrap();
                     return Ok(Some(definition))
                 } else {
                     // Expected an instance of something
                     return Err(())
+                }
+            }
             // Nothing is concrete yet
             Ok(None)
+        }
         let (progress_subject, progress_expr) = match &mut expr.field {
             Field::Length => {
                 let progress_subject = self.apply_forced_constraint(ctx, subject_id, &ARRAYLIKE_TEMPLATE)?;
                 let progress_expr = self.apply_forced_constraint(ctx, upcast_id, &INTEGERLIKE_TEMPLATE)?;
                 (progress_subject, progress_expr)
             },
             Field::Symbolic(field) => {
                 // Retrieve the struct definition id and field index if possible
                 // and not previously determined
                 if field.definition.is_none() {
                     // Not yet known, check if we can determine it
                     let subject_type = self.expr_types.get(&subject_id).unwrap();
                     let type_def = determine_inference_type_instance(&ctx.types, subject_type);
                     match type_def {
                         Ok(Some(type_def)) => {
                             // Subject type is known, check if it is a
                             // struct and the field exists on the struct
                             let struct_def = if let DefinedTypeVariant::Struct(struct_def) = &type_def.definition {
                                 struct_def
                             } else {
                                 return Err(ParseError::new_error(
                                     &ctx.module.source, field.identifier.position,
                                     &format!(
                                         "Can only apply field access to structs, got a subject of type '{}'",
                                         subject_type.display_name(&ctx.heap)
+                                    )
                                 ));
                             };
                             for (field_def_idx, field_def) in struct_def.fields.iter().enumerate() {
                                 if field_def.identifier == field.identifier {
                                     // Set field definition and index
                                     field.definition = Some(type_def.ast_definition);
                                     field.field_idx = field_def_idx;
                                     break;
+                                }
+                            }
                             if field.definition.is_none() {
                                 let field_position = field.identifier.position;
                                 let ast_struct_def = ctx.heap[type_def.ast_definition].as_struct();
                                 return Err(ParseError::new_error(
                                     &ctx.module.source, field_position,
                                     &format!(
                                         "This field does not exist on the struct '{}'",
                                         &String::from_utf8_lossy(&ast_struct_def.identifier.value)
+                                    )
                                 ))
+                            }
                             // Encountered definition and field index for the
                             // first time
                             self.insert_initial_select_polymorph_data(ctx, id);
                         },
                         Ok(None) => {
                             // Type of subject is not yet known, so we
                             // cannot make any progress yet
                             return Ok(())
                         },
                         Err(()) => {
                             return Err(ParseError::new_error(
                                 &ctx.module.source, field.identifier.position,
                                 &format!(
                                     "Can only apply field access to structs, got a subject of type '{}'",
                                     subject_type.display_name(&ctx.heap)
+                                )
                             ));
+                        }
+                    }
+                }
                 // If here then field definition and index are known, and the
                 // initial type (based on the struct's definition) has been
                 // applied.
                 // Check to see if we can infer anything about the subject's and
                 // the field's polymorphic variables
                 let poly_data = self.extra_data.get_mut(&upcast_id).unwrap();
                 let mut poly_progress = HashSet::new();
                 // Apply to struct's type
                 let signature_type: *mut _ = &mut poly_data.embedded[0];
                 let subject_type: *mut _ = self.expr_types.get_mut(&subject_id).unwrap();
                 let (_, progress_subject) = Self::apply_equal2_signature_constraint(
                     ctx, upcast_id, Some(subject_id), poly_data, &mut poly_progress,
                     signature_type, 0, subject_type, 0
                 )?;
                 if progress_subject {
                     self.expr_queued.insert(subject_id);
+                }
                 // Apply to field's type
                 let signature_type: *mut _ = &mut poly_data.returned;
                 let expr_type: *mut _ = self.expr_types.get_mut(&upcast_id).unwrap();
                 let (_, progress_expr) = Self::apply_equal2_signature_constraint(
                     ctx, upcast_id, None, poly_data, &mut poly_progress,
                     signature_type, 0, expr_type, 0
                 )?;
                 if progress_expr {
                     if let Some(parent_id) = ctx.heap[upcast_id].parent_expr_id() {
                         self.expr_queued.insert(parent_id);
+                    }
+                }
                 // Reapply progress in polymorphic variables to struct's type
                 let signature_type: *mut _ = &mut poly_data.embedded[0];
                 let subject_type: *mut _ = self.expr_types.get_mut(&subject_id).unwrap();
                 let progress_subject = Self::apply_equal2_polyvar_constraint(&ctx.heap,
                     poly_data, &poly_progress, signature_type, subject_type
                 );
                 let signature_type: *mut _ = &mut poly_data.returned;
                 let expr_type: *mut _ = self.expr_types.get_mut(&upcast_id).unwrap();
                 let progress_expr = Self::apply_equal2_polyvar_constraint(&ctx.heap,
                     poly_data, &poly_progress, signature_type, expr_type
                 );
                 (progress_subject, progress_expr)
+            }
         };
         if progress_subject { self.queue_expr(subject_id); }
         if progress_expr { self.queue_expr_parent(ctx, upcast_id); }
         debug_log!(" * After:");
         debug_log!("   - Subject type [{}]: {}", progress_subject, self.expr_types.get(&subject_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Expr    type [{}]: {}", progress_expr, self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         Ok(())
+    }
     fn progress_array_expr(&mut self, ctx: &mut Ctx, id: ArrayExpressionId) -> Result<(), ParseError> {
         let upcast_id = id.upcast();
         let expr = &ctx.heap[id];
         let expr_elements = expr.elements.clone(); // TODO: @performance
         debug_log!("Array expr ({} elements): {}", expr_elements.len(), upcast_id.index);
         debug_log!(" * Before:");
         debug_log!("   - Expr type: {}", self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         // All elements should have an equal type
         let progress = self.apply_equal_n_constraint(ctx, upcast_id, &expr_elements)?;
         for (progress_arg, arg_id) in progress.iter().zip(expr_elements.iter()) {
             if *progress_arg {
                 self.queue_expr(*arg_id);
+            }
+        }
         // And the output should be an array of the element types
         let mut expr_progress = self.apply_forced_constraint(ctx, upcast_id, &ARRAY_TEMPLATE)?;
         if !expr_elements.is_empty() {
             let first_arg_id = expr_elements[0];
             let (inner_expr_progress, arg_progress) = self.apply_equal2_constraint(
                 ctx, upcast_id, upcast_id, 1, first_arg_id, 0
             )?;
             expr_progress = expr_progress || inner_expr_progress;
             // Note that if the array type progressed the type of the arguments,
             // then we should enqueue this progression function again
             // TODO: @fix Make apply_equal_n accept a start idx as well
             if arg_progress { self.queue_expr(upcast_id); }
+        }
         debug_log!(" * After:");
         debug_log!("   - Expr type [{}]: {}", expr_progress, self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         if expr_progress { self.queue_expr_parent(ctx, upcast_id); }
         Ok(())
+    }
     fn progress_literal_expr(&mut self, ctx: &mut Ctx, id: LiteralExpressionId) -> Result<(), ParseError> {
         let upcast_id = id.upcast();
         let expr = &ctx.heap[id];
         debug_log!("Literal expr: {}", upcast_id.index);
         debug_log!(" * Before:");
         debug_log!("   - Expr type: {}", self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         let progress_expr = match &expr.value {
             Literal::Null => {
                 self.apply_forced_constraint(ctx, upcast_id, &MESSAGE_TEMPLATE)?
             },
             Literal::Integer(_) => {
                 self.apply_forced_constraint(ctx, upcast_id, &INTEGERLIKE_TEMPLATE)?
             },
             Literal::True | Literal::False => {
                 self.apply_forced_constraint(ctx, upcast_id, &BOOL_TEMPLATE)?
             },
             Literal::Character(_) => todo!("character literals"),
             Literal::Struct(data) => {
                 let extra = self.extra_data.get_mut(&upcast_id).unwrap();
                 for poly in &extra.poly_vars {
                     debug_log!(" * Poly: {}", poly.display_name(&ctx.heap));
+                }
                 let mut poly_progress = HashSet::new();
                 debug_assert_eq!(extra.embedded.len(), data.fields.len());
                 debug_log!(" * During (inferring types from fields and struct type):");
                 // Mutually infer field signature/expression types
                 for (field_idx, field) in data.fields.iter().enumerate() {
                     let field_expr_id = field.value;
                     let signature_type: *mut _ = &mut extra.embedded[field_idx];
                     let field_type: *mut _ = self.expr_types.get_mut(&field_expr_id).unwrap();
                     let (_, progress_arg) = Self::apply_equal2_signature_constraint(
                         ctx, upcast_id, Some(field_expr_id), extra, &mut poly_progress,
                         signature_type, 0, field_type, 0
                     )?;
                     debug_log!(
                         "   - Field {} type | sig: {}, field: {}", field_idx,
                         unsafe{&*signature_type}.display_name(&ctx.heap),
                         unsafe{&*field_type}.display_name(&ctx.heap)
                     );
                     if progress_arg {
                         self.expr_queued.insert(field_expr_id);
+                    }
+                }
                 debug_log!("   - Field poly progress | {:?}", poly_progress);
                 // Same for the type of the struct itself
                 let signature_type: *mut _ = &mut extra.returned;
                 let expr_type: *mut _ = self.expr_types.get_mut(&upcast_id).unwrap();
                 let (_, progress_expr) = Self::apply_equal2_signature_constraint(
                     ctx, upcast_id, None, extra, &mut poly_progress,
                     signature_type, 0, expr_type, 0
                 )?;
                 debug_log!(
                     "   - Ret type | sig: {}, expr: {}",
                     unsafe{&*signature_type}.display_name(&ctx.heap),
                     unsafe{&*expr_type}.display_name(&ctx.heap)
                 );
                 debug_log!("   - Ret poly progress | {:?}", poly_progress);
                 if progress_expr {
                     // TODO: @cleanup, cannot call utility self.queue_parent thingo
                     if let Some(parent_id) = ctx.heap[upcast_id].parent_expr_id() {
                         self.expr_queued.insert(parent_id);
+                    }
+                }
                 // Check which expressions use the polymorphic arguments. If the
                 // polymorphic variables have been progressed then we try to
                 // progress them inside the expression as well.
                 debug_log!(" * During (reinferring from progressed polyvars):");
                 // For all field expressions
                 for field_idx in 0..extra.embedded.len() {
                     debug_assert_eq!(field_idx, data.fields[field_idx].field_idx, "confusing, innit?");
                     let signature_type: *mut _ = &mut extra.embedded[field_idx];
                     let field_expr_id = data.fields[field_idx].value;
                     let field_type: *mut _ = self.expr_types.get_mut(&field_expr_id).unwrap();
                     let progress_arg = Self::apply_equal2_polyvar_constraint(&ctx.heap,
                         extra, &poly_progress, signature_type, field_type
                     );
                     debug_log!(
                         "   - Field {} type | sig: {}, field: {}", field_idx,
                         unsafe{&*signature_type}.display_name(&ctx.heap),
                         unsafe{&*field_type}.display_name(&ctx.heap)
                     );
                     if progress_arg {
                         self.expr_queued.insert(field_expr_id);
+                    }
+                }
                 // For the return type
                 let signature_type: *mut _ = &mut extra.returned;
                 let expr_type: *mut _ = self.expr_types.get_mut(&upcast_id).unwrap();
                 let progress_expr = Self::apply_equal2_polyvar_constraint(
                     &ctx.heap, extra, &poly_progress, signature_type, expr_type
                 );
                 progress_expr
             },
             Literal::Enum(_) => {
                 let extra = self.extra_data.get_mut(&upcast_id).unwrap();
                 for poly in &extra.poly_vars {
                     debug_log!(" * Poly: {}", poly.display_name(&ctx.heap));
+                }
                 let mut poly_progress = HashSet::new();
                 debug_log!(" * During (inferring types from return type)");
                 let signature_type: *mut _ = &mut extra.returned;
                 let expr_type: *mut _ = self.expr_types.get_mut(&upcast_id).unwrap();
                 let (_, progress_expr) = Self::apply_equal2_signature_constraint(
                     ctx, upcast_id, None, extra, &mut poly_progress,
                     signature_type, 0, expr_type, 0
                 )?;
                 debug_log!(
                     "   - Ret type | sig: {}, expr: {}",
                     unsafe{&*signature_type}.display_name(&ctx.heap),
                     unsafe{&*expr_type}.display_name(&ctx.heap)
                 );
                 if progress_expr {
                     // TODO: @cleanup
                     if let Some(parent_id) = ctx.heap[upcast_id].parent_expr_id() {
                         self.expr_queued.insert(parent_id);
+                    }
+                }
                 debug_log!(" * During (reinferring from progress polyvars):");
                 let progress_expr = Self::apply_equal2_polyvar_constraint(
                     &ctx.heap, extra, &poly_progress, signature_type, expr_type
                 );
                 progress_expr
             },
             Literal::Union(data) => {
                 let extra = self.extra_data.get_mut(&upcast_id).unwrap();
                 for poly in &extra.poly_vars {
                     debug_log!(" * Poly: {}", poly.display_name(&ctx.heap));
+                }
                 let mut poly_progress = HashSet::new();
                 debug_assert_eq!(extra.embedded.len(), data.values.len());
                 debug_log!(" * During (inferring types from variant values and union type):");
                 // Mutually infer union variant values
                 for (value_idx, value_expr_id) in data.values.iter().enumerate() {
                     let value_expr_id = *value_expr_id;
                     let signature_type: *mut _ = &mut extra.embedded[value_idx];
                     let value_type: *mut _ = self.expr_types.get_mut(&value_expr_id).unwrap();
                     let (_, progress_arg) = Self::apply_equal2_signature_constraint(
                         ctx, upcast_id, Some(value_expr_id), extra, &mut poly_progress,
                         signature_type, 0, value_type, 0
                     )?;
                     debug_log!(
                         "   - Value {} type | sig: {}, field: {}", value_idx,
                         unsafe{&*signature_type}.display_name(&ctx.heap),
                         unsafe{&*value_type}.display_name(&ctx.heap)
                     );
                     if progress_arg {
                         self.expr_queued.insert(value_expr_id);
+                    }
+                }
                 debug_log!("   - Field poly progress | {:?}", poly_progress);
                 // Infer type of union itself
                 let signature_type: *mut _ = &mut extra.returned;
                 let expr_type: *mut _ = self.expr_types.get_mut(&upcast_id).unwrap();
                 let (_, progress_expr) = Self::apply_equal2_signature_constraint(
                     ctx, upcast_id, None, extra, &mut poly_progress,
                     signature_type, 0, expr_type, 0
                 )?;
                 debug_log!(
                     "   - Ret type | sig: {}, expr: {}",
                     unsafe{&*signature_type}.display_name(&ctx.heap),
                     unsafe{&*expr_type}.display_name(&ctx.heap)
                 );
                 debug_log!("   - Ret poly progress | {:?}", poly_progress);
                 if progress_expr {
                     // TODO: @cleanup, borrowing rules
                     if let Some(parent_id) = ctx.heap[upcast_id].parent_expr_id() {
                         self.expr_queued.insert(parent_id);
+                    }
+                }
                 debug_log!(" * During (reinferring from progress polyvars):");
                 // For all embedded values of the union variant
                 for value_idx in 0..extra.embedded.len() {
                     let signature_type: *mut _ = &mut extra.embedded[value_idx];
                     let value_expr_id = data.values[value_idx];
                     let value_type: *mut _ = self.expr_types.get_mut(&value_expr_id).unwrap();
                     let progress_arg = Self::apply_equal2_polyvar_constraint(
                         &ctx.heap, extra, &poly_progress, signature_type, value_type
                     );
                     debug_log!(
                         "   - Value {} type | sig: {}, value: {}", value_idx,
                         unsafe{&*signature_type}.display_name(&ctx.heap),
                         unsafe{&*value_type}.display_name(&ctx.heap)
                     );
@@ @@ -2273,1335 +2274,1336 @@ impl TypeResolvingVisitor { @@
         debug_log!(
             "   - Ret type | sig: {}, expr: {}",
             unsafe{&*signature_type}.display_name(&ctx.heap),
             unsafe{&*expr_type}.display_name(&ctx.heap)
         );
         if progress_expr {
             // TODO: @cleanup, cannot call utility self.queue_parent thingo
             if let Some(parent_id) = ctx.heap[upcast_id].parent_expr_id() {
                 self.expr_queued.insert(parent_id);
+            }
+        }
         // If we did not have an error in the polymorph inference above, then
         // reapplying the polymorph type to each argument type and the return
         // type should always succeed.
         debug_log!(" * During (reinferring from progressed polyvars):");
         for (poly_idx, poly_var) in extra.poly_vars.iter().enumerate() {
             debug_log!("   - Poly {} | sig: {}", poly_idx, poly_var.display_name(&ctx.heap));
+        }
         // TODO: @performance If the algorithm is changed to be more "on demand
         //  argument re-evaluation", instead of "all-argument re-evaluation",
         //  then this is no longer true
         for arg_idx in 0..extra.embedded.len() {
             let signature_type: *mut _ = &mut extra.embedded[arg_idx];
             let arg_expr_id = expr.arguments[arg_idx];
             let arg_type: *mut _ = self.expr_types.get_mut(&arg_expr_id).unwrap();
             let progress_arg = Self::apply_equal2_polyvar_constraint(&ctx.heap,
                 extra, &poly_progress,
                 signature_type, arg_type
             );
             debug_log!(
                 "   - Arg {} type | sig: {}, arg: {}", arg_idx,
                 unsafe{&*signature_type}.display_name(&ctx.heap),
                 unsafe{&*arg_type}.display_name(&ctx.heap)
             );
             if progress_arg {
                 self.expr_queued.insert(arg_expr_id);
+            }
+        }
         // Once more for the return type
         let signature_type: *mut _ = &mut extra.returned;
         let ret_type: *mut _ = self.expr_types.get_mut(&upcast_id).unwrap();
         let progress_ret = Self::apply_equal2_polyvar_constraint(&ctx.heap,
             extra, &poly_progress, signature_type, ret_type
         );
         debug_log!(
             "   - Ret type | sig: {}, arg: {}",
             unsafe{&*signature_type}.display_name(&ctx.heap),
             unsafe{&*ret_type}.display_name(&ctx.heap)
         );
         if progress_ret {
             self.queue_expr_parent(ctx, upcast_id);
+        }
         debug_log!(" * After:");
         debug_log!("   - Expr type: {}", self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         Ok(())
+    }
     fn progress_variable_expr(&mut self, ctx: &mut Ctx, id: VariableExpressionId) -> Result<(), ParseError> {
         let upcast_id = id.upcast();
         let var_expr = &ctx.heap[id];
         let var_id = var_expr.declaration.unwrap();
         debug_log!("Variable expr '{}': {}", &String::from_utf8_lossy(&ctx.heap[var_id].identifier().value), upcast_id.index);
         debug_log!(" * Before:");
         debug_log!("   - Var  type: {}", self.var_types.get(&var_id).unwrap().var_type.display_name(&ctx.heap));
         debug_log!("   - Expr type: {}", self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         // Retrieve shared variable type and expression type and apply inference
         let var_data = self.var_types.get_mut(&var_id).unwrap();
         let expr_type = self.expr_types.get_mut(&upcast_id).unwrap();
         let infer_res = unsafe{ InferenceType::infer_subtrees_for_both_types(
             &mut var_data.var_type as *mut _, 0, expr_type, 0
         ) };
         if infer_res == DualInferenceResult::Incompatible {
             let var_decl = &ctx.heap[var_id];
             return Err(ParseError::new_error(
                 &ctx.module.source, var_decl.position(),
                 &format!(
                     "Conflicting types for this variable, previously assigned the type '{}'",
                     var_data.var_type.display_name(&ctx.heap)
+                )
             ).with_postfixed_info(
                 &ctx.module.source, var_expr.position,
                 &format!(
                     "But inferred to have incompatible type '{}' here",
                     expr_type.display_name(&ctx.heap)
+                )
             ))
+        }
         let progress_var = infer_res.modified_lhs();
         let progress_expr = infer_res.modified_rhs();
         if progress_var {
             // Let other variable expressions using this type progress as well
             for other_expr in var_data.used_at.iter() {
                 if *other_expr != upcast_id {
                     self.expr_queued.insert(*other_expr);
+                }
+            }
             // Let a linked port know that our type has updated
             if let Some(linked_id) = var_data.linked_var {
                 // Only perform one-way inference to prevent updating our type, this
                 // would lead to an inconsistency
                 let var_type: *mut _ = &mut var_data.var_type;
                 let link_data = self.var_types.get_mut(&linked_id).unwrap();
                 debug_assert!(
                     unsafe{&*var_type}.parts[0] == InferenceTypePart::Input ||
                     unsafe{&*var_type}.parts[0] == InferenceTypePart::Output
                 );
                 debug_assert!(
                     link_data.var_type.parts[0] == InferenceTypePart::Input ||
                     link_data.var_type.parts[0] == InferenceTypePart::Output
                 );
                 match InferenceType::infer_subtree_for_single_type(&mut link_data.var_type, 1, &unsafe{&*var_type}.parts, 1) {
                     SingleInferenceResult::Modified => {
                         for other_expr in &link_data.used_at {
                             self.expr_queued.insert(*other_expr);
+                        }
                     },
                     SingleInferenceResult::Unmodified => {},
                     SingleInferenceResult::Incompatible => {
                         let var_data = self.var_types.get(&var_id).unwrap();
                         let link_data = self.var_types.get(&linked_id).unwrap();
                         let var_decl = &ctx.heap[var_id];
                         let link_decl = &ctx.heap[linked_id];
                         return Err(ParseError::new_error(
                             &ctx.module.source, var_decl.position(),
                             &format!(
                                 "Conflicting types for this variable, assigned the type '{}'",
                                 var_data.var_type.display_name(&ctx.heap)
+                            )
                         ).with_postfixed_info(
                             &ctx.module.source, link_decl.position(),
                             &format!(
                                 "Because it is incompatible with this variable, assigned the type '{}'",
                                 link_data.var_type.display_name(&ctx.heap)
+                            )
                         ));
+                    }
+                }
+            }
+        }
         if progress_expr { self.queue_expr_parent(ctx, upcast_id); }
         debug_log!(" * After:");
         debug_log!("   - Var  type [{}]: {}", progress_var, self.var_types.get(&var_id).unwrap().var_type.display_name(&ctx.heap));
         debug_log!("   - Expr type [{}]: {}", progress_expr, self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         Ok(())
+    }
     fn queue_expr_parent(&mut self, ctx: &Ctx, expr_id: ExpressionId) {
         if let ExpressionParent::Expression(parent_expr_id, _) = &ctx.heap[expr_id].parent() {
             self.expr_queued.insert(*parent_expr_id);
+        }
+    }
     fn queue_expr(&mut self, expr_id: ExpressionId) {
         self.expr_queued.insert(expr_id);
+    }
     /// Applies a forced type constraint: the type associated with the supplied
     /// expression will be molded into the provided "template". The template may
     /// be fully specified (e.g. a bool) or contain "inference" variables (e.g.
     /// an array of T)
     fn apply_forced_constraint(
         &mut self, ctx: &mut Ctx, expr_id: ExpressionId, template: &[InferenceTypePart]
     ) -> Result<bool, ParseError> {
         debug_assert_expr_ids_unique_and_known!(self, expr_id);
         let expr_type = self.expr_types.get_mut(&expr_id).unwrap();
         match InferenceType::infer_subtree_for_single_type(expr_type, 0, template, 0) {
             SingleInferenceResult::Modified => Ok(true),
             SingleInferenceResult::Unmodified => Ok(false),
             SingleInferenceResult::Incompatible => Err(
                 self.construct_template_type_error(ctx, expr_id, template)
+            )
+        }
+    }
     fn apply_forced_constraint_types(
         to_infer: *mut InferenceType, to_infer_start_idx: usize,
         template: &[InferenceTypePart], template_start_idx: usize
     ) -> Result<bool, ()> {
         match InferenceType::infer_subtree_for_single_type(
             unsafe{ &mut *to_infer }, to_infer_start_idx,
             template, template_start_idx
         ) {
             SingleInferenceResult::Modified => Ok(true),
             SingleInferenceResult::Unmodified => Ok(false),
             SingleInferenceResult::Incompatible => Err(()),
+        }
+    }
     /// 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, expr_id: ExpressionId,
         arg1_id: ExpressionId, arg1_start_idx: usize,
         arg2_id: ExpressionId, arg2_start_idx: usize
     ) -> Result<(bool, bool), ParseError> {
         debug_assert_expr_ids_unique_and_known!(self, arg1_id, arg2_id);
         let arg1_type: *mut _ = self.expr_types.get_mut(&arg1_id).unwrap();
         let arg2_type: *mut _ = self.expr_types.get_mut(&arg2_id).unwrap();
         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, expr_id, arg1_id, arg2_id));
+        }
         Ok((infer_res.modified_lhs(), infer_res.modified_rhs()))
+    }
     /// Applies an equal2 constraint between a signature type (e.g. a function
     /// argument or struct field) and an expression whose type should match that
     /// expression. If we make progress on the signature, then we try to see if
     /// any of the embedded polymorphic types can be progressed.
     ///
     /// `outer_expr_id` is the main expression we're progressing (e.g. a
     /// function call), while `expr_id` is the embedded expression we're
     /// matching against the signature. `expression_type` and
     /// `expression_start_idx` belong to `expr_id`.
     fn apply_equal2_signature_constraint(
         ctx: &Ctx, outer_expr_id: ExpressionId, expr_id: Option<ExpressionId>,
         polymorph_data: &mut ExtraData, polymorph_progress: &mut HashSet<usize>,
         signature_type: *mut InferenceType, signature_start_idx: usize,
         expression_type: *mut InferenceType, expression_start_idx: usize
     ) -> Result<(bool, bool), ParseError> {
         // Safety: cannot mutually infer the same types
         //         polymorph_data containers may not be modified
         debug_assert_ptrs_distinct!(signature_type, expression_type);
         // Infer the signature and expression type
         let infer_res = unsafe {
             InferenceType::infer_subtrees_for_both_types(
                 signature_type, signature_start_idx,
                 expression_type, expression_start_idx
+            )
         };
         if infer_res == DualInferenceResult::Incompatible {
             // TODO: Check if I still need to use this
             let outer_position = ctx.heap[outer_expr_id].position();
             let (position_name, position) = match expr_id {
                 Some(expr_id) => ("argument's", ctx.heap[expr_id].position()),
                 None => ("type's", outer_position)
             };
             let (signature_display_type, expression_display_type) = unsafe { (
                 (&*signature_type).display_name(&ctx.heap),
                 (&*expression_type).display_name(&ctx.heap)
             ) };
             return Err(ParseError::new_error(
                 &ctx.module.source, outer_position,
                 "Failed to fully resolve the types of this expression"
             ).with_postfixed_info(
                 &ctx.module.source, position,
                 &format!(
                     "Because the {} signature has been resolved to '{}', but the expression has been resolved to '{}'",
                     position_name, signature_display_type, expression_display_type
+                )
             ));
+        }
         // Try to see if we can progress any of the polymorphic variables
         let progress_sig = infer_res.modified_lhs();
         let progress_expr = infer_res.modified_rhs();
         if progress_sig {
             let signature_type = unsafe{&mut *signature_type};
             debug_assert!(
                 signature_type.has_body_marker,
                 "made progress on signature type, but it doesn't have a marker"
             );
             for (poly_idx, poly_section) in signature_type.body_marker_iter() {
                 let polymorph_type = &mut polymorph_data.poly_vars[poly_idx];
                 match Self::apply_forced_constraint_types(
                     polymorph_type, 0, poly_section, 0
                 ) {
                     Ok(true) => { polymorph_progress.insert(poly_idx); },
                     Ok(false) => {},
                     Err(()) => { return Err(Self::construct_poly_arg_error(ctx, polymorph_data, outer_expr_id))}
+                }
+            }
+        }
         Ok((progress_sig, progress_expr))
+    }
     /// Applies equal2 constraints on the signature type for each of the
     /// polymorphic variables. If the signature type is progressed then we
     /// progress the expression type as well.
     ///
     /// This function assumes that the polymorphic variables have already been
     /// progressed as far as possible by calling
     /// `apply_equal2_signature_constraint`. As such, we expect to not encounter
     /// any errors.
     ///
     /// This function returns true if the expression's type has been progressed
     fn apply_equal2_polyvar_constraint(
         heap: &Heap,
         polymorph_data: &ExtraData, _polymorph_progress: &HashSet<usize>,
         signature_type: *mut InferenceType, expr_type: *mut InferenceType
     ) -> bool {
         // Safety: all pointers should be distinct
         //         polymorph_data contains may not be modified
         debug_assert_ptrs_distinct!(signature_type, expr_type);
         let signature_type = unsafe{&mut *signature_type};
         let expr_type = unsafe{&mut *expr_type};
         // Iterate through markers in signature type to try and make progress
         // on the polymorphic variable
         let mut seek_idx = 0;
         let mut modified_sig = false;
         while let Some((poly_idx, start_idx)) = signature_type.find_body_marker(seek_idx) {
             let end_idx = InferenceType::find_subtree_end_idx(&signature_type.parts, start_idx);
             // if polymorph_progress.contains(&poly_idx) {
                 // Need to match subtrees
                 let polymorph_type = &polymorph_data.poly_vars[poly_idx];
                 debug_log!("   - DEBUG: Applying {} to '{}' from '{}'", polymorph_type.display_name(heap), InferenceType::partial_display_name(heap, &signature_type.parts[start_idx..]), signature_type.display_name(heap));
                 let modified_at_marker = Self::apply_forced_constraint_types(
                     signature_type, start_idx,
                     &polymorph_type.parts, 0
                 ).expect("no failure when applying polyvar constraints");
                 modified_sig = modified_sig || modified_at_marker;
             // }
             seek_idx = end_idx;
+        }
         // If we made any progress on the signature's type, then we also need to
         // apply it to the expression that is supposed to match the signature.
         if modified_sig {
             match InferenceType::infer_subtree_for_single_type(
                 expr_type, 0, &signature_type.parts, 0
             ) {
                 SingleInferenceResult::Modified => true,
                 SingleInferenceResult::Unmodified => false,
                 SingleInferenceResult::Incompatible =>
                     unreachable!("encountered failure while reapplying modified signature to expression after polyvar inference")
+            }
         } else {
             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, expr_id: ExpressionId,
         arg1_id: ExpressionId, arg2_id: ExpressionId,
         start_idx: usize
     ) -> Result<(bool, bool, bool), ParseError> {
         // Safety: all expression IDs are always distinct, and we do not modify
         //  the container
         debug_assert_expr_ids_unique_and_known!(self, expr_id, arg1_id, arg2_id);
         let expr_type: *mut _ = self.expr_types.get_mut(&expr_id).unwrap();
         let arg1_type: *mut _ = self.expr_types.get_mut(&arg1_id).unwrap();
         let arg2_type: *mut _ = self.expr_types.get_mut(&arg2_id).unwrap();
         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, expr_id, arg1_id));
+        }
         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, expr_id, arg1_id, arg2_id));
+        }
         // 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))
+    }
     // TODO: @optimize Since we only deal with a single type this might be done
     //  a lot more efficiently, methinks (disregarding the allocations here)
     fn apply_equal_n_constraint(
         &mut self, ctx: &Ctx, expr_id: ExpressionId, args: &[ExpressionId],
     ) -> Result<Vec<bool>, ParseError> {
         // Early exit
         match args.len() {
 => return Ok(vec!()),         // nothing to progress
 => return Ok(vec![false]),    // only one type, so nothing to infer
             _ => {}
+        }
         let mut progress = Vec::new();
         progress.resize(args.len(), false);
         // Do pairwise inference, keep track of the last entry we made progress
         // on. Once done we need to update everything to the most-inferred type.
         let mut arg_iter = args.iter();
         let mut last_arg_id = *arg_iter.next().unwrap();
         let mut last_lhs_progressed = 0;
         let mut lhs_arg_idx = 0;
         while let Some(next_arg_id) = arg_iter.next() {
             let arg1_type: *mut _ = self.expr_types.get_mut(&last_arg_id).unwrap();
             let arg2_type: *mut _ = self.expr_types.get_mut(next_arg_id).unwrap();
             let res = unsafe {
                 InferenceType::infer_subtrees_for_both_types(arg1_type, 0, arg2_type, 0)
             };
             if res == DualInferenceResult::Incompatible {
                 return Err(self.construct_arg_type_error(ctx, expr_id, last_arg_id, *next_arg_id));
+            }
             if res.modified_lhs() {
                 // We re-inferred something on the left hand side, so everything
                 // up until now should be re-inferred.
                 progress[lhs_arg_idx] = true;
                 last_lhs_progressed = lhs_arg_idx;
+            }
             progress[lhs_arg_idx + 1] = res.modified_rhs();
             last_arg_id = *next_arg_id;
             lhs_arg_idx += 1;
+        }
         // Re-infer everything. Note that we do not need to re-infer the type
         // exactly at `last_lhs_progressed`, but only everything up to it.
         let last_type: *mut _ = self.expr_types.get_mut(args.last().unwrap()).unwrap();
         for arg_idx in 0..last_lhs_progressed {
             let arg_type: *mut _ = self.expr_types.get_mut(&args[arg_idx]).unwrap();
             unsafe{
                 (*arg_type).replace_subtree(0, &(*last_type).parts);
+            }
             progress[arg_idx] = true;
+        }
         Ok(progress)
+    }
     /// Determines the `InferenceType` for the expression based on the
     /// expression parent. Note that if the parent is another expression, we do
     /// not take special action, instead we let parent expressions fix the type
     /// of subexpressions before they have a chance to call this function.
     fn insert_initial_expr_inference_type(
         &mut self, ctx: &mut Ctx, expr_id: ExpressionId
     ) -> Result<(), ParseError> {
         use ExpressionParent as EP;
         use InferenceTypePart as ITP;
         let expr = &ctx.heap[expr_id];
         let inference_type = match expr.parent() {
             EP::None =>
                 // Should have been set by linker
                 unreachable!(),
             EP::ExpressionStmt(_) | EP::Expression(_, _) =>
                 // Determined during type inference
                 InferenceType::new(false, false, vec![ITP::Unknown]),
             EP::If(_) | EP::While(_) | EP::Assert(_) =>
                 // Must be a boolean
                 InferenceType::new(false, true, vec![ITP::Bool]),
             EP::Return(_) =>
                 // Must match the return type of the function
                 if let DefinitionType::Function(func_id) = self.definition_type {
                     let return_parser_type_id = ctx.heap[func_id].return_type;
                     self.determine_inference_type_from_parser_type(ctx, return_parser_type_id, true)
                 } else {
                     // Cannot happen: definition always set upon body traversal
                     // and "return" calls in components are illegal.
                     unreachable!();
                 },
             EP::New(_) =>
                 // Must be a component call, which we assign a "Void" return
                 // type
                 InferenceType::new(false, true, vec![ITP::Void]),
         };
         match self.expr_types.entry(expr_id) {
             Entry::Vacant(vacant) => {
                 vacant.insert(inference_type);
             },
             Entry::Occupied(mut preexisting) => {
                 // We already have an entry, this happens if our parent fixed
                 // our type (e.g. we're used in a conditional expression's test)
                 // but we have a different type.
                 // TODO: Is this ever called? Seems like it can't
                 debug_assert!(false, "I am actually called, my ID is {}", expr_id.index);
                 let old_type = preexisting.get_mut();
                 if let SingleInferenceResult::Incompatible = InferenceType::infer_subtree_for_single_type(
                     old_type, 0, &inference_type.parts, 0
                 ) {
                     return Err(self.construct_expr_type_error(ctx, expr_id, expr_id))
+                }
+            }
+        }
         Ok(())
+    }
     fn insert_initial_call_polymorph_data(
         &mut self, ctx: &mut Ctx, call_id: CallExpressionId
     ) {
         use InferenceTypePart as ITP;
         // 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 variables themselves
         let mut poly_vars = Vec::with_capacity(call.poly_args.len());
         for poly_arg_type_id in call.poly_args.clone() { // TODO: @performance
             poly_vars.push(self.determine_inference_type_from_parser_type(ctx, poly_arg_type_id, true));
+        }
         // Handle the arguments
         // TODO: @cleanup: Maybe factor this out for reuse in the validator/linker, should also
         //  make the code slightly more robust.
         let (embedded_types, return_type) = match &call.method {
             Method::Create => {
                 // Not polymorphic
+                (
                     vec![InferenceType::new(false, true, vec![ITP::Int])],
                     InferenceType::new(false, true, vec![ITP::Message, ITP::Byte])
+                )
             },
             Method::Fires => {
                 // bool fires<T>(PortLike<T> arg)
+                (
                     vec![InferenceType::new(true, false, vec![ITP::PortLike, ITP::MarkerBody(0), ITP::Unknown])],
                     InferenceType::new(false, true, vec![ITP::Bool])
+                )
             },
             Method::Get => {
                 // T get<T>(input<T> arg)
+                (
                     vec![InferenceType::new(true, false, vec![ITP::Input, ITP::MarkerBody(0), ITP::Unknown])],
                     InferenceType::new(true, false, vec![ITP::MarkerBody(0), ITP::Unknown])
+                )
             },
             Method::Put => {
                 // void Put<T>(output<T> port, T msg)
+                (
                     vec![
                         InferenceType::new(true, false, vec![ITP::Output, ITP::MarkerBody(0), ITP::Unknown]),
                         InferenceType::new(true, false, vec![ITP::MarkerBody(0), ITP::Unknown])
                     ],
                     InferenceType::new(false, true, vec![ITP::Void])
+                )
+            }
             Method::Symbolic(symbolic) => {
                 let definition = &ctx.heap[symbolic.definition.unwrap()];
                 match definition {
                     Definition::Component(definition) => {
                         debug_assert_eq!(poly_vars.len(), definition.poly_vars.len());
                         let mut parameter_types = Vec::with_capacity(definition.parameters.len());
                         for param_id in definition.parameters.clone() {
                             let param = &ctx.heap[param_id];
                             let param_parser_type_id = param.parser_type;
                             parameter_types.push(self.determine_inference_type_from_parser_type(ctx, param_parser_type_id, false));
+                        }
                         (parameter_types, InferenceType::new(false, true, vec![InferenceTypePart::Void]))
                     },
                     Definition::Function(definition) => {
                         debug_assert_eq!(poly_vars.len(), definition.poly_vars.len());
                         let mut parameter_types = Vec::with_capacity(definition.parameters.len());
                         for param_id in definition.parameters.clone() {
                             let param = &ctx.heap[param_id];
                             let param_parser_type_id = param.parser_type;
                             parameter_types.push(self.determine_inference_type_from_parser_type(ctx, param_parser_type_id, false));
+                        }
                         let return_type = self.determine_inference_type_from_parser_type(ctx, definition.return_type, false);
                         (parameter_types, return_type)
                     },
                     Definition::Struct(_) | Definition::Enum(_) | Definition::Union(_) => {
                         unreachable!("insert initial polymorph data for struct/enum/union");
+                    }
+                }
+            }
         };
         self.extra_data.insert(call_id.upcast(), ExtraData {
             poly_vars,
             embedded: embedded_types,
             returned: return_type
         });
+    }
     fn insert_initial_struct_polymorph_data(
         &mut self, ctx: &mut Ctx, lit_id: LiteralExpressionId,
     ) {
         use InferenceTypePart as ITP;
         let literal = ctx.heap[lit_id].value.as_struct();
         // Handle polymorphic arguments
         let mut poly_vars = Vec::with_capacity(literal.poly_args2.len());
         let mut total_num_poly_parts = 0;
         for poly_arg_type_id in literal.poly_args2.clone() { // TODO: @performance
             let inference_type = self.determine_inference_type_from_parser_type(
                 ctx, poly_arg_type_id, true
             );
             total_num_poly_parts += inference_type.parts.len();
             poly_vars.push(inference_type);
+        }
         // Handle parser types on struct definition
         let definition = &ctx.heap[literal.definition.unwrap()];
         let definition = match definition {
             Definition::Struct(definition) => {
                 debug_assert_eq!(poly_vars.len(), definition.poly_vars.len());
                 definition
             },
             _ => unreachable!("definition for struct literal does not point to struct definition")
         };
         // 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(definition.fields.len());
         for lit_field in literal.fields.iter() {
             let def_field = &definition.fields[lit_field.field_idx];
             let inference_type = self.determine_inference_type_from_parser_type(
                 ctx, def_field.parser_type, 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_vars.len() + total_num_poly_parts;
         let mut parts = Vec::with_capacity(parts_reserved);
         parts.push(ITP::Instance(definition.this.upcast(), poly_vars.len()));
         let mut return_type_done = true;
         for (poly_var_idx, poly_var) in poly_vars.iter().enumerate() {
             if !poly_var.is_done { return_type_done = false; }
             parts.push(ITP::MarkerBody(poly_var_idx));
             parts.extend(poly_var.parts.iter().cloned());
+        }
         debug_assert_eq!(parts.len(), parts_reserved);
         let return_type = InferenceType::new(!poly_vars.is_empty(), return_type_done, parts);
         self.extra_data.insert(lit_id.upcast(), ExtraData{
             poly_vars,
             embedded: embedded_types,
             returned: return_type,
         });
+    }
     /// 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
     ) {
         use InferenceTypePart as ITP;
         let literal = ctx.heap[lit_id].value.as_enum();
         // Handle polymorphic arguments to the enum
         let mut poly_vars = Vec::with_capacity(literal.poly_args2.len());
         let mut total_num_poly_parts = 0;
         for poly_arg_type_id in literal.poly_args2.clone() { // TODO: @performance
             let inference_type = self.determine_inference_type_from_parser_type(
                 ctx, poly_arg_type_id, true
             );
             total_num_poly_parts += inference_type.parts.len();
             poly_vars.push(inference_type);
+        }
         // Handle enum type itself
         let parts_reserved = 1 + poly_vars.len() + total_num_poly_parts;
         let mut parts = Vec::with_capacity(parts_reserved);
         parts.push(ITP::Instance(literal.definition.unwrap(), poly_vars.len()));
         let mut enum_type_done = true;
         for (poly_var_idx, poly_var) in poly_vars.iter().enumerate() {
             if !poly_var.is_done { enum_type_done = false; }
             parts.push(ITP::MarkerBody(poly_var_idx));
             parts.extend(poly_var.parts.iter().cloned());
+        }
         debug_assert_eq!(parts.len(), parts_reserved);
         let enum_type = InferenceType::new(!poly_vars.is_empty(), enum_type_done, parts);
         self.extra_data.insert(lit_id.upcast(), ExtraData{
             poly_vars,
             embedded: Vec::new(),
             returned: enum_type,
         });
+    }
     /// 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
     ) {
         use InferenceTypePart as ITP;
         let literal = ctx.heap[lit_id].value.as_union();
         // Construct the polymorphic variables
         let mut poly_vars = Vec::with_capacity(literal.poly_args2.len());
         let mut total_num_poly_parts = 0;
         for poly_arg_type_id in literal.poly_args2.clone() { // TODO: @performance
             let inference_type = self.determine_inference_type_from_parser_type(
                 ctx, poly_arg_type_id, true
             );
             total_num_poly_parts += inference_type.parts.len();
             poly_vars.push(inference_type);
+        }
         // Handle any of the embedded values in the variant, if specified
         let definition_id = literal.definition.unwrap();
         let union_definition = ctx.types.get_base_definition(&definition_id)
             .unwrap()
             .definition.as_union();
         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_id in &variant_definition.embedded {
             let inference_type = self.determine_inference_type_from_parser_type(
-                ctx, *embedded_id, true
+                ctx, *embedded_id, false
             );
             embedded.push(inference_type);
+        }
         // Handle the type of the union itself
         let parts_reserved = 1 + poly_vars.len() + total_num_poly_parts;
         let mut parts = Vec::with_capacity(parts_reserved);
         parts.push(ITP::Instance(definition_id, poly_vars.len()));
         let mut union_type_done = true;
         for (poly_var_idx, poly_var) in poly_vars.iter().enumerate() {
             if !poly_var.is_done { union_type_done = false; }
             parts.push(ITP::MarkerBody(poly_var_idx));
             parts.extend(poly_var.parts.iter().cloned());
+        }
         debug_assert_eq!(parts_reserved, parts.len());
         let union_type = InferenceType::new(!poly_vars.is_empty(), union_type_done, parts);
         self.extra_data.insert(lit_id.upcast(), ExtraData{
             poly_vars,
             embedded,
             returned: union_type
         });
+    }
     /// Inserts the extra polymorphic data struct. Assumes that the select
     /// expression's referenced (definition_id, field_idx) has been resolved.
     fn insert_initial_select_polymorph_data(
         &mut self, ctx: &Ctx, select_id: SelectExpressionId
     ) {
         use InferenceTypePart as ITP;
         // Retrieve relevant data
         let expr = &ctx.heap[select_id];
         let field = expr.field.as_symbolic();
         let definition_id = field.definition.unwrap();
         let definition = ctx.heap[definition_id].as_struct();
         let field_idx = field.field_idx;
         // Generate initial polyvar types and struct type
         let num_poly_vars = definition.poly_vars.len();
         let mut poly_vars = Vec::with_capacity(num_poly_vars);
         let struct_parts_reserved = 1 + 2 * num_poly_vars;
         let mut struct_parts = Vec::with_capacity(struct_parts_reserved);
         struct_parts.push(ITP::Instance(definition_id, num_poly_vars));
         for poly_idx in 0..num_poly_vars {
             poly_vars.push(InferenceType::new(true, false, vec![
                 ITP::MarkerBody(poly_idx), ITP::Unknown,
             ]));
             struct_parts.push(ITP::MarkerBody(poly_idx));
             struct_parts.push(ITP::Unknown);
+        }
         debug_assert_eq!(struct_parts.len(), struct_parts_reserved);
         // Generate initial field type
         let field_type = self.determine_inference_type_from_parser_type(
             ctx, definition.fields[field_idx].parser_type, false
         );
         self.extra_data.insert(select_id.upcast(), ExtraData{
             poly_vars,
             embedded: vec![InferenceType::new(num_poly_vars != 0, num_poly_vars == 0, struct_parts)],
             returned: field_type
         });
+    }
     /// Determines the initial InferenceType from the provided ParserType. This
     /// may be called with two kinds of intentions:
     /// 1. To resolve a ParserType within the body of a function, or on
     ///     polymorphic arguments to calls/instantiations within that body. This
     ///     means that the polymorphic variables are known and can be replaced
     ///     with the monomorph we're instantiating.
     /// 2. To resolve a ParserType on a called function's definition or on
     ///     an instantiated datatype's members. This means that the polymorphic
     ///     arguments inside those ParserTypes refer to the polymorphic
     ///     variables in the called/instantiated type's definition.
     /// In the second case we place InferenceTypePart::Marker instances such
     /// that we can perform type inference on the polymorphic variables.
     fn determine_inference_type_from_parser_type(
         &mut self, ctx: &Ctx, parser_type_id: ParserTypeId,
         parser_type_in_body: bool
     ) -> InferenceType {
         use ParserTypeVariant as PTV;
         use InferenceTypePart as ITP;
         let mut to_consider = VecDeque::with_capacity(16);
         to_consider.push_back(parser_type_id);
         let mut infer_type = Vec::new();
         let mut has_inferred = false;
         let mut has_markers = false;
         while !to_consider.is_empty() {
             let parser_type_id = to_consider.pop_front().unwrap();
             let parser_type = &ctx.heap[parser_type_id];
             match &parser_type.variant {
                 PTV::Message => {
                     // TODO: @types Remove the Message -> Byte hack at some point...
                     infer_type.push(ITP::Message);
                     infer_type.push(ITP::Byte);
                 },
                 PTV::Bool => { infer_type.push(ITP::Bool); },
                 PTV::Byte => { infer_type.push(ITP::Byte); },
                 PTV::Short => { infer_type.push(ITP::Short); },
                 PTV::Int => { infer_type.push(ITP::Int); },
                 PTV::Long => { infer_type.push(ITP::Long); },
                 PTV::String => { infer_type.push(ITP::String); },
                 PTV::IntegerLiteral => { unreachable!("integer literal type on variable type"); },
                 PTV::Inferred => {
                     infer_type.push(ITP::Unknown);
                     has_inferred = true;
                 },
                 PTV::Array(subtype_id) => {
                     infer_type.push(ITP::Array);
                     to_consider.push_front(*subtype_id);
                 },
                 PTV::Input(subtype_id) => {
                     infer_type.push(ITP::Input);
                     to_consider.push_front(*subtype_id);
                 },
                 PTV::Output(subtype_id) => {
                     infer_type.push(ITP::Output);
                     to_consider.push_front(*subtype_id);
                 },
                 PTV::Symbolic(symbolic) => {
                     debug_assert!(symbolic.variant.is_some(), "symbolic variant not yet determined");
                     match symbolic.variant.as_ref().unwrap() {
                         SymbolicParserTypeVariant::PolyArg(_, arg_idx) => {
                             let arg_idx = *arg_idx;
                             debug_assert!(symbolic.poly_args2.is_empty()); // TODO: @hkt
                             if parser_type_in_body {
                                 // Polymorphic argument refers to definition's
                                 // polymorphic variables
                                 debug_assert!(arg_idx < self.poly_vars.len());
                                 debug_assert!(!self.poly_vars[arg_idx].has_marker());
                                 infer_type.push(ITP::MarkerDefinition(arg_idx));
                                 for concrete_part in &self.poly_vars[arg_idx].parts {
                                     infer_type.push(ITP::from(*concrete_part));
+                                }
                             } else {
                                 // Polymorphic argument has to be inferred
                                 has_markers = true;
                                 has_inferred = true;
                                 infer_type.push(ITP::MarkerBody(arg_idx));
                                 infer_type.push(ITP::Unknown);
+                            }
                         },
                         SymbolicParserTypeVariant::Definition(definition_id) => {
                             // TODO: @cleanup
                             if cfg!(debug_assertions) {
                                 let definition = &ctx.heap[*definition_id];
                                 debug_assert!(definition.is_struct() || definition.is_enum()); // TODO: @function_ptrs
+                                debug_assert!(definition.is_struct() || definition.is_enum() || definition.is_union()); // TODO: @function_ptrs
                                 let num_poly = match definition {
                                     Definition::Struct(v) => v.poly_vars.len(),
                                     Definition::Enum(v) => v.poly_vars.len(),
                                     Definition::Union(v) => v.poly_vars.len(),
                                     _ => unreachable!(),
                                 };
                                 debug_assert_eq!(symbolic.poly_args2.len(), num_poly);
+                            }
                             infer_type.push(ITP::Instance(*definition_id, symbolic.poly_args2.len()));
                             let mut poly_arg_idx = symbolic.poly_args2.len();
                             while poly_arg_idx > 0 {
                                 poly_arg_idx -= 1;
                                 to_consider.push_front(symbolic.poly_args2[poly_arg_idx]);
+                            }
+                        }
+                    }
+                }
+            }
+        }
         InferenceType::new(has_markers, !has_inferred, infer_type)
+    }
     /// Construct an error when an expression's type does not match. This
     /// happens if we infer the expression type from its arguments (e.g. the
     /// expression type of an addition operator is the type of the arguments)
     /// But the expression type was already set due to our parent (e.g. an
     /// "if statement" or a "logical not" always expecting a boolean)
     fn construct_expr_type_error(
         &self, ctx: &Ctx, expr_id: ExpressionId, arg_id: ExpressionId
     ) -> ParseError {
         // TODO: Expand and provide more meaningful information for humans
         let expr = &ctx.heap[expr_id];
         let arg_expr = &ctx.heap[arg_id];
         let expr_type = self.expr_types.get(&expr_id).unwrap();
         let arg_type = self.expr_types.get(&arg_id).unwrap();
         return ParseError::new_error(
             &ctx.module.source, expr.position(),
             &format!(
                 "Incompatible types: this expression expected a '{}'",
                 expr_type.display_name(&ctx.heap)
+            )
         ).with_postfixed_info(
             &ctx.module.source, arg_expr.position(),
             &format!(
                 "But this expression yields a '{}'",
                 arg_type.display_name(&ctx.heap)
+            )
+        )
+    }
     fn construct_arg_type_error(
         &self, ctx: &Ctx, expr_id: ExpressionId,
         arg1_id: ExpressionId, arg2_id: ExpressionId
     ) -> ParseError {
         let expr = &ctx.heap[expr_id];
         let arg1 = &ctx.heap[arg1_id];
         let arg2 = &ctx.heap[arg2_id];
         let arg1_type = self.expr_types.get(&arg1_id).unwrap();
         let arg2_type = self.expr_types.get(&arg2_id).unwrap();
         return ParseError::new_error(
             &ctx.module.source, expr.position(),
             "Incompatible types: cannot apply this expression"
         ).with_postfixed_info(
             &ctx.module.source, arg1.position(),
             &format!(
                 "Because this expression has type '{}'",
                 arg1_type.display_name(&ctx.heap)
+            )
         ).with_postfixed_info(
             &ctx.module.source, arg2.position(),
             &format!(
                 "But this expression has type '{}'",
                 arg2_type.display_name(&ctx.heap)
+            )
+        )
+    }
     fn construct_template_type_error(
         &self, ctx: &Ctx, expr_id: ExpressionId, template: &[InferenceTypePart]
     ) -> ParseError {
         let expr = &ctx.heap[expr_id];
         let expr_type = self.expr_types.get(&expr_id).unwrap();
         return ParseError::new_error(
             &ctx.module.source, expr.position(),
             &format!(
                 "Incompatible types: got a '{}' but expected a '{}'",
                 expr_type.display_name(&ctx.heap),
                 InferenceType::partial_display_name(&ctx.heap, template)
+            )
+        )
+    }
     /// Constructs a human interpretable error in the case that type inference
     /// on a polymorphic variable to a function call or literal construction
     /// failed. This may only be caused by a pair of inference types (which may
     /// come from arguments or the return type) having two different inferred
     /// values for that polymorphic variable.
     ///
     /// So we find this pair and construct the error using it.
     ///
     /// We assume that the expression is a function call or a struct literal,
     /// and that an actual error has occurred.
     fn construct_poly_arg_error(
         ctx: &Ctx, poly_data: &ExtraData, expr_id: ExpressionId
     ) -> ParseError {
         // Helper function to check for polymorph mismatch between two inference
         // types.
         fn has_poly_mismatch<'a>(type_a: &'a InferenceType, type_b: &'a InferenceType) -> Option<(usize, &'a [InferenceTypePart], &'a [InferenceTypePart])> {
             if !type_a.has_body_marker || !type_b.has_body_marker {
                 return None
+            }
             for (marker_a, section_a) in type_a.body_marker_iter() {
                 for (marker_b, section_b) in type_b.body_marker_iter() {
                     if marker_a != marker_b {
                         // Not the same polymorphic variable
                         continue;
+                    }
                     if !InferenceType::check_subtrees(section_a, 0, section_b, 0) {
                         // Not compatible
                         return Some((marker_a, section_a, section_b))
+                    }
+                }
+            }
             None
+        }
         // Helpers function to retrieve polyvar name and definition name
         fn get_poly_var_and_func_name(ctx: &Ctx, poly_var_idx: usize, expr: &CallExpression) -> (String, String) {
             match &expr.method {
                 Method::Create => unreachable!(),
                 Method::Fires => (String::from('T'), String::from("fires")),
                 Method::Get => (String::from('T'), String::from("get")),
                 Method::Put => (String::from('T'), String::from("put")),
                 Method::Symbolic(symbolic) => {
                     let definition = &ctx.heap[symbolic.definition.unwrap()];
                     let poly_var = match definition {
                         Definition::Struct(_) | Definition::Enum(_) | Definition::Union(_) => unreachable!(),
                         Definition::Function(definition) => {
                             String::from_utf8_lossy(&definition.poly_vars[poly_var_idx].value).to_string()
                         },
                         Definition::Component(definition) => {
                             String::from_utf8_lossy(&definition.poly_vars[poly_var_idx].value).to_string()
+                        }
                     };
                     let func_name = String::from_utf8_lossy(&symbolic.identifier.value).to_string();
                     (poly_var, func_name)
+                }
+            }
+        }
         fn get_poly_var_and_type_name(ctx: &Ctx, poly_var_idx: usize, definition_id: DefinitionId) -> (String, String) {
             let definition = &ctx.heap[definition_id];
             let (poly_var_name, type_name) = match definition {
                 Definition::Function(_) | Definition::Component(_) =>
                     unreachable!("get_poly_var_and_type_name called on unsupported type"),
                 Definition::Enum(definition) => (
                     &definition.poly_vars[poly_var_idx].value,
                     &definition.identifier.value
                 ),
                 Definition::Struct(definition) => (
                     &definition.poly_vars[poly_var_idx].value,
                     &definition.identifier.value
                 ),
                 Definition::Union(definition) => (
                     &definition.poly_vars[poly_var_idx].value,
                     &definition.identifier.value
                 ),
             };
+            (
                 String::from_utf8_lossy(poly_var_name).to_string(),
                 String::from_utf8_lossy(type_name).to_string()
+            )
+        }
         // Helper function to construct initial error
         fn construct_main_error(ctx: &Ctx, poly_var_idx: usize, expr: &Expression) -> ParseError {
             match expr {
                 Expression::Call(expr) => {
                     let (poly_var, func_name) = get_poly_var_and_func_name(ctx, poly_var_idx, expr);
                     return ParseError::new_error(
                         &ctx.module.source, expr.position(),
                         &format!(
                             "Conflicting type for polymorphic variable '{}' of '{}'",
                             poly_var, func_name
+                        )
+                    )
                 },
                 Expression::Literal(expr) => {
                     let definition_id = match &expr.value {
                         Literal::Struct(v) => v.definition.unwrap(),
                         Literal::Enum(v) => v.definition.unwrap(),
                         Literal::Union(v) => v.definition.unwrap(),
                         _ => unreachable!(),
                     };
                     let (poly_var, struct_name) = get_poly_var_and_type_name(ctx, poly_var_idx, definition_id);
                     return ParseError::new_error(
                         &ctx.module.source, expr.position(),
                         &format!(
                             "Conflicting type for polymorphic variable '{}' of instantiation of '{}'",
                             poly_var, struct_name
+                        )
+                    )
                 },
                 Expression::Select(expr) => {
                     let field = expr.field.as_symbolic();
                     let (poly_var, struct_name) = get_poly_var_and_type_name(ctx, poly_var_idx, field.definition.unwrap());
                     return ParseError::new_error(
                         &ctx.module.source, expr.position(),
                         &format!(
                             "Conflicting type for polymorphic variable '{}' while accessing field '{}' of '{}'",
                             poly_var, &String::from_utf8_lossy(&field.identifier.value), struct_name
+                        )
+                    )
+                }
                 _ => unreachable!("called construct_poly_arg_error without a call/literal expression")
+            }
+        }
         // Actual checking
         let expr = &ctx.heap[expr_id];
         let (expr_args, expr_return_name) = match expr {
             Expression::Call(expr) =>
+                (
                     expr.arguments.clone(),
                     "return type"
                 ),
             Expression::Literal(expr) => {
                 let expressions = match &expr.value {
                     Literal::Struct(v) => v.fields.iter()
                         .map(|f| f.value)
                         .collect(),
                     Literal::Enum(_) => Vec::new(),
                     Literal::Union(v) => v.values.clone(),
                     _ => unreachable!()
                 };
                 ( expressions, "literal" )
             },
             Expression::Select(expr) =>
                 // Select expression uses the polymorphic variables of the
                 // struct it is accessing, so get the subject expression.
+                (
                     vec![expr.subject],
                     "selected field"
                 ),
             _ => unreachable!(),
         };
         // - check return type with itself
         if let Some((poly_idx, section_a, section_b)) = has_poly_mismatch(
             &poly_data.returned, &poly_data.returned
         ) {
             return construct_main_error(ctx, poly_idx, expr)
                 .with_postfixed_info(
                     &ctx.module.source, expr.position(),
                     &format!(
                         "The {} inferred the conflicting types '{}' and '{}'",
                         expr_return_name,
                         InferenceType::partial_display_name(&ctx.heap, section_a),
                         InferenceType::partial_display_name(&ctx.heap, section_b)
+                    )
+                )
+        }
         // - check arguments with each other argument and with return type
         for (arg_a_idx, arg_a) in poly_data.embedded.iter().enumerate() {
             for (arg_b_idx, arg_b) in poly_data.embedded.iter().enumerate() {
                 if arg_b_idx > arg_a_idx {
                     break;
+                }
                 if let Some((poly_idx, section_a, section_b)) = has_poly_mismatch(&arg_a, &arg_b) {
                     let error = construct_main_error(ctx, poly_idx, expr);
                     if arg_a_idx == arg_b_idx {
                         // Same argument
                         let arg = &ctx.heap[expr_args[arg_a_idx]];
                         return error.with_postfixed_info(
                             &ctx.module.source, arg.position(),
                             &format!(
                                 "This argument inferred the conflicting types '{}' and '{}'",
                                 InferenceType::partial_display_name(&ctx.heap, section_a),
                                 InferenceType::partial_display_name(&ctx.heap, section_b)
+                            )
+                        )
                     } else {
                         let arg_a = &ctx.heap[expr_args[arg_a_idx]];
                         let arg_b = &ctx.heap[expr_args[arg_b_idx]];
                         return error.with_postfixed_info(
                             &ctx.module.source, arg_a.position(),
                             &format!(
                                 "This argument inferred it to '{}'",
                                 InferenceType::partial_display_name(&ctx.heap, section_a)
+                            )
                         ).with_postfixed_info(
                             &ctx.module.source, arg_b.position(),
                             &format!(
                                 "While this argument inferred it to '{}'",
                                 InferenceType::partial_display_name(&ctx.heap, section_b)
+                            )
+                        )
+                    }
+                }
+            }
             // Check with return type
             if let Some((poly_idx, section_arg, section_ret)) = has_poly_mismatch(arg_a, &poly_data.returned) {
                 let arg = &ctx.heap[expr_args[arg_a_idx]];
                 return construct_main_error(ctx, poly_idx, expr)
                     .with_postfixed_info(
                         &ctx.module.source, arg.position(),
                         &format!(
                             "This argument inferred it to '{}'",
                             InferenceType::partial_display_name(&ctx.heap, section_arg)
+                        )
+                    )
                     .with_postfixed_info(
                         &ctx.module.source, expr.position(),
                         &format!(
                             "While the {} inferred it to '{}'",
                             expr_return_name,
                             InferenceType::partial_display_name(&ctx.heap, section_ret)
+                        )
+                    )
+            }
+        }
         unreachable!("construct_poly_arg_error without actual error found?")
+    }
+}
 #[cfg(test)]
 mod tests {
     use super::*;
     use crate::protocol::arena::Id;
     use InferenceTypePart as ITP;
     use InferenceType as IT;
     #[test]
     fn test_single_part_inference() {
         // lhs argument inferred from rhs
         let pairs = [
             (ITP::NumberLike, ITP::Byte),
             (ITP::IntegerLike, ITP::Int),
             (ITP::Unknown, ITP::Long),
             (ITP::Unknown, ITP::String)
         ];
         for (lhs, rhs) in pairs.iter() {
             // Using infer-both
             let mut lhs_type = IT::new(false, false, vec![lhs.clone()]);
             let mut rhs_type = IT::new(false, true, vec![rhs.clone()]);
             let result = unsafe{ IT::infer_subtrees_for_both_types(
                 &mut lhs_type, 0, &mut rhs_type, 0
             ) };
             assert_eq!(DualInferenceResult::First, result);
             assert_eq!(lhs_type.parts, rhs_type.parts);
             // Using infer-single
             let mut lhs_type = IT::new(false, false, vec![lhs.clone()]);
             let rhs_type = IT::new(false, true, vec![rhs.clone()]);
             let result = IT::infer_subtree_for_single_type(
                 &mut lhs_type, 0, &rhs_type.parts, 0
             );
             assert_eq!(SingleInferenceResult::Modified, result);
             assert_eq!(lhs_type.parts, rhs_type.parts);
+        }
+    }
     #[test]
     fn test_multi_part_inference() {
         let pairs = [
             (vec![ITP::ArrayLike, ITP::NumberLike], vec![ITP::Slice, ITP::Byte]),
             (vec![ITP::Unknown], vec![ITP::Input, ITP::Array, ITP::String]),
             (vec![ITP::PortLike, ITP::Int], vec![ITP::Input, ITP::Int]),
             (vec![ITP::Unknown], vec![ITP::Output, ITP::Int]),
+            (
                 vec![ITP::Instance(Id::new(0), 2), ITP::Input, ITP::Unknown, ITP::Output, ITP::Unknown],
                 vec![ITP::Instance(Id::new(0), 2), ITP::Input, ITP::Array, ITP::Int, ITP::Output, ITP::Int]
+            )
         ];
         for (lhs, rhs) in pairs.iter() {
             let mut lhs_type = IT::new(false, false, lhs.clone());
             let mut rhs_type = IT::new(false, true, rhs.clone());
             let result = unsafe{ IT::infer_subtrees_for_both_types(
                 &mut lhs_type, 0, &mut rhs_type, 0
             ) };
             assert_eq!(DualInferenceResult::First, result);
             assert_eq!(lhs_type.parts, rhs_type.parts);
             let mut lhs_type = IT::new(false, false, lhs.clone());
             let rhs_type = IT::new(false, true, rhs.clone());
             let result = IT::infer_subtree_for_single_type(
                 &mut lhs_type, 0, &rhs_type.parts, 0
             );
             assert_eq!(SingleInferenceResult::Modified, result);
             assert_eq!(lhs_type.parts, rhs_type.parts)
+        }
+    }
+}
@@ \ No newline at end of file @@

src/protocol/parser/type_table.rs

➞

Show inline comments

 /**
 TypeTable
 Contains the type table: a datastructure that, when compilation succeeds,
 contains a concrete type definition for each AST type definition. In general
 terms the type table will go through the following phases during the compilation
 process:
 . The base type definitions are resolved after the parser phase has
     finished. This implies that the AST is fully constructed, but not yet
     annotated.
 . With the base type definitions resolved, the validation/linker phase will
     use the type table (together with the symbol table) to disambiguate
     terms (e.g. does an expression refer to a variable, an enum, a constant,
     etc.)
 . During the type checking/inference phase the type table is used to ensure
     that the AST contains valid use of types in expressions and statements.
     At the same time type inference will find concrete instantiations of
     polymorphic types, these will be stored in the type table as monomorphed
     instantiations of a generic type.
 . After type checking and inference (and possibly when constructing byte
     code) the type table will construct a type graph and solidify each
     non-polymorphic type and monomorphed instantiations of polymorphic types
     into concrete types.
 So a base type is defined by its (optionally polymorphic) representation in the
 AST. A concrete type has concrete types for each of the polymorphic arguments. A
 struct, enum or union may have polymorphic arguments but not actually be a
 polymorphic type. This happens when the polymorphic arguments are not used in
 the type definition itself. Similarly for functions/components: but here we just
 check the arguments/return type of the signature.
 Apart from base types and concrete types, we also use the term "embedded type"
 for types that are embedded within another type, such as a type of a struct
 struct field or of a union variant. Embedded types may themselves have
 polymorphic arguments and therefore form an embedded type tree.
 NOTE: for now a polymorphic definition of a function/component is illegal if the
     polymorphic arguments are not used in the arguments/return type. It should
     be legal, but we disallow it for now.
 TODO: Allow potentially cyclic datatypes and reject truly cyclic datatypes.
 TODO: Allow for the full potential of polymorphism
 TODO: Detect "true" polymorphism: for datatypes like structs/enum/unions this
     is simple. For functions we need to check the entire body. Do it here? Or
     do it somewhere else?
 TODO: Do we want to check fn argument collision here, or in validation phase?
 TODO: Make type table an on-demand thing instead of constructing all base types.
 TODO: Cleanup everything, feels like a lot can be written cleaner and with less
     assumptions on each function call.
 // TODO: Review all comments
 */
 use std::fmt::{Formatter, Result as FmtResult};
 use std::collections::{HashMap, VecDeque};
 use crate::protocol::ast::*;
 use crate::protocol::parser::symbol_table::{SymbolTable, Symbol};
 use crate::protocol::inputsource::*;
 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 {
         *self == TypeClass::Enum || *self == TypeClass::Union || *self == TypeClass::Struct
+    }
     pub(crate) fn is_proc_type(&self) -> bool {
         *self == TypeClass::Function || *self == TypeClass::Component
+    }
+}
 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<PolyVar>,
     pub(crate) is_polymorph: bool,
     pub(crate) is_pointerlike: bool,
     // TODO: @optimize
     pub(crate) monomorphs: Vec<Vec<ConcreteType>>,
+}
 impl DefinedType {
     fn add_monomorph(&mut self, types: Vec<ConcreteType>) {
         debug_assert!(!self.has_monomorph(&types), "monomorph already exists");
         self.monomorphs.push(types);
+    }
     pub(crate) fn has_any_monomorph(&self) -> bool {
         !self.monomorphs.is_empty()
+    }
     pub(crate) fn has_monomorph(&self, types: &Vec<ConcreteType>) -> bool {
         debug_assert_eq!(self.poly_vars.len(), types.len(), "mismatch in number of polymorphic types");
         for monomorph in &self.monomorphs {
             if monomorph == types { return true; }
+        }
         return false;
+    }
+}
 pub enum DefinedTypeVariant {
     Enum(EnumType),
     Union(UnionType),
     Struct(StructType),
     Function(FunctionType),
     Component(ComponentType)
+}
 pub struct PolyVar {
     identifier: Identifier,
     /// Whether the polymorphic variables is used directly in the definition of
     /// the type (not including bodies of function/component types)
     is_in_use: bool,
+}
 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())
+        }
+    }
+}
 /// `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(crate) variants: Vec<EnumVariant>,
     pub(crate) representation: PrimitiveType,
+}
 // TODO: Also support maximum u64 value
 pub struct EnumVariant {
     pub(crate) identifier: Identifier,
     pub(crate) 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.
 pub struct UnionType {
     pub(crate) variants: Vec<UnionVariant>,
     pub(crate) tag_representation: PrimitiveType
+}
 pub struct UnionVariant {
     pub(crate) identifier: Identifier,
     pub(crate) embedded: Vec<ParserTypeId>, // zero-length does not have embedded values
     pub(crate) tag_value: i64,
+}
 pub struct StructType {
     pub(crate) fields: Vec<StructField>,
+}
 pub struct StructField {
     pub(crate) identifier: Identifier,
     pub(crate) parser_type: ParserTypeId,
+}
 pub struct FunctionType {
     pub return_type: ParserTypeId,
     pub arguments: Vec<FunctionArgument>
+}
 pub struct ComponentType {
     pub variant: ComponentVariant,
     pub arguments: Vec<FunctionArgument>
+}
 pub struct FunctionArgument {
     identifier: Identifier,
     parser_type: ParserTypeId,
+}
 //------------------------------------------------------------------------------
 // Type table
 //------------------------------------------------------------------------------
 // TODO: @cleanup Do I really need this, doesn't make the code that much cleaner
 struct TypeIterator {
     breadcrumbs: Vec<(RootId, DefinitionId)>
+}
 impl TypeIterator {
     fn new() -> Self {
         Self{ breadcrumbs: Vec::with_capacity(32) }
+    }
     fn reset(&mut self, root_id: RootId, definition_id: DefinitionId) {
         self.breadcrumbs.clear();
         self.breadcrumbs.push((root_id, definition_id))
+    }
     fn push(&mut self, root_id: RootId, definition_id: DefinitionId) {
         self.breadcrumbs.push((root_id, definition_id));
+    }
     fn contains(&self, root_id: RootId, definition_id: DefinitionId) -> bool {
         for (stored_root_id, stored_definition_id) in self.breadcrumbs.iter() {
             if *stored_root_id == root_id && *stored_definition_id == definition_id { return true; }
+        }
         return false
+    }
     fn top(&self) -> Option<(RootId, DefinitionId)> {
         self.breadcrumbs.last().map(|(r, d)| (*r, *d))
+    }
     fn pop(&mut self) {
         debug_assert!(!self.breadcrumbs.is_empty());
         self.breadcrumbs.pop();
+    }
+}
 /// Result from attempting to resolve a `ParserType` using the symbol table and
 /// the type table.
 enum ResolveResult {
     /// ParserType is a builtin type
     BuiltIn,
     /// ParserType points to a polymorphic argument, contains the index of the
     /// polymorphic argument in the outermost definition (e.g. we may have
     /// structs nested three levels deep, but in the innermost struct we can
     /// only use the polyargs that are specified in the type definition of the
     /// outermost struct).
     PolyArg(usize),
     /// ParserType points to a user-defined type that is already resolved in the
     /// type table.
     Resolved((RootId, DefinitionId)),
     /// ParserType points to a user-defined type that is not yet resolved into
     /// the type table.
     Unresolved((RootId, DefinitionId))
+}
 pub(crate) struct TypeTable {
     /// Lookup from AST DefinitionId to a defined type. Considering possible
     /// polymorphs is done inside the `DefinedType` struct.
     lookup: HashMap<DefinitionId, DefinedType>,
     /// Iterator over `(module, definition)` tuples used as workspace to make sure
     /// that each base definition of all a type's subtypes are resolved.
     iter: TypeIterator,
     /// Iterator over `parser type`s during the process where `parser types` are
     /// resolved into a `(module, definition)` tuple.
     parser_type_iter: VecDeque<ParserTypeId>,
+}
 pub(crate) struct TypeCtx<'a> {
     symbols: &'a SymbolTable,
     heap: &'a mut Heap,
     modules: &'a [LexedModule]
+}
 impl<'a> TypeCtx<'a> {
     pub(crate) fn new(symbols: &'a SymbolTable, heap: &'a mut Heap, modules: &'a [LexedModule]) -> Self {
         Self{ symbols, heap, modules }
+    }
+}
 impl TypeTable {
     /// Construct a new type table without any resolved types.
     pub(crate) fn new() -> Self {
         Self{
             lookup: HashMap::new(),
             iter: TypeIterator::new(),
             parser_type_iter: VecDeque::with_capacity(64),
+        }
+    }
     pub(crate) fn build_base_types(&mut self, ctx: &mut TypeCtx) -> Result<(), ParseError> {
         // Make sure we're allowed to cast root_id to index into ctx.modules
         debug_assert!(self.lookup.is_empty());
         debug_assert!(self.iter.top().is_none());
         debug_assert!(self.parser_type_iter.is_empty());
         if cfg!(debug_assertions) {
             for (index, module) in ctx.modules.iter().enumerate() {
                 debug_assert_eq!(index, module.root_id.index as usize);
+            }
+        }
         // Use context to guess hashmap size
         let reserve_size = ctx.heap.definitions.len();
         self.lookup.reserve(reserve_size);
         // TODO: @cleanup Rework this hack
         for root_idx in 0..ctx.modules.len() {
             let last_definition_idx = ctx.heap[ctx.modules[root_idx].root_id].definitions.len();
             for definition_idx in 0..last_definition_idx {
                 let definition_id = ctx.heap[ctx.modules[root_idx].root_id].definitions[definition_idx];
                 self.resolve_base_definition(ctx, definition_id)?;
+            }
+        }
         debug_assert_eq!(self.lookup.len(), reserve_size, "mismatch in reserved size of type table");
         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
     pub(crate) fn get_base_definition(&self, definition_id: &DefinitionId) -> Option<&DefinedType> {
         self.lookup.get(&definition_id)
+    }
     /// Instantiates a monomorph for a given base definition.
     pub(crate) fn add_monomorph(&mut self, definition_id: &DefinitionId, types: Vec<ConcreteType>) {
         debug_assert!(
             self.lookup.contains_key(definition_id),
             "attempting to instantiate monomorph of definition unknown to type table"
         );
         let definition = self.lookup.get_mut(definition_id).unwrap();
         definition.add_monomorph(types);
+    }
     /// Checks if a given definition already has a specific monomorph
     pub(crate) fn has_monomorph(&mut self, definition_id: &DefinitionId, types: &Vec<ConcreteType>) -> bool {
         debug_assert!(
             self.lookup.contains_key(definition_id),
             "attempting to check monomorph existence of definition unknown to type table"
         );
         let definition = self.lookup.get(definition_id).unwrap();
         definition.has_monomorph(types)
+    }
     /// This function will resolve just the basic definition of the type, it
     /// will not handle any of the monomorphized instances of the type.
     fn resolve_base_definition<'a>(&'a mut self, ctx: &mut TypeCtx, definition_id: DefinitionId) -> Result<(), ParseError> {
         // Check if we have already resolved the base definition
         if self.lookup.contains_key(&definition_id) { return Ok(()); }
         let root_id = Self::find_root_id(ctx, definition_id);
         self.iter.reset(root_id, definition_id);
         while let Some((root_id, definition_id)) = self.iter.top() {
             // We have a type to resolve
             let definition = &ctx.heap[definition_id];
             let can_pop_breadcrumb = match definition {
                 // TODO: @cleanup Borrow rules hax
                 Definition::Enum(_) => self.resolve_base_enum_definition(ctx, root_id, definition_id),
                 Definition::Union(_) => self.resolve_base_union_definition(ctx, root_id, definition_id),
                 Definition::Struct(_) => self.resolve_base_struct_definition(ctx, root_id, definition_id),
                 Definition::Component(_) => self.resolve_base_component_definition(ctx, root_id, definition_id),
                 Definition::Function(_) => self.resolve_base_function_definition(ctx, root_id, definition_id),
             }?;
             // Otherwise: `ingest_resolve_result` has pushed a new breadcrumb
             // that we must follow before we can resolve the current type
             if can_pop_breadcrumb {
                 self.iter.pop();
+            }
+        }
         // We must have resolved the type
         debug_assert!(self.lookup.contains_key(&definition_id), "base type not resolved");
         Ok(())
+    }
     /// Resolve the basic enum definition to an entry in the type table. It will
     /// not instantiate any monomorphized instances of polymorphic enum
     /// definitions. If a subtype has to be resolved first then this function
     /// will return `false` after calling `ingest_resolve_result`.
     fn resolve_base_enum_definition(&mut self, ctx: &mut TypeCtx, root_id: RootId, definition_id: DefinitionId) -> Result<bool, ParseError> {
         debug_assert!(ctx.heap[definition_id].is_enum());
         debug_assert!(!self.lookup.contains_key(&definition_id), "base enum already resolved");
         let definition = ctx.heap[definition_id].as_enum();
         let mut enum_value = -1;
         let mut min_enum_value = 0;
         let mut max_enum_value = 0;
         let mut variants = Vec::with_capacity(definition.variants.len());
         for variant in &definition.variants {
             enum_value += 1;
             match &variant.value {
                 EnumVariantValue::None => {
                     variants.push(EnumVariant{
                         identifier: variant.identifier.clone(),
                         value: enum_value,
                     });
                 },
                 EnumVariantValue::Integer(override_value) => {
                     enum_value = *override_value;
                     variants.push(EnumVariant{
                         identifier: variant.identifier.clone(),
                         value: enum_value,
                     });
+                }
+            }
             if enum_value < min_enum_value { min_enum_value = enum_value; }
             else if enum_value > max_enum_value { max_enum_value = enum_value; }
+        }
         // Ensure enum names and polymorphic args do not conflict
         self.check_identifier_collision(
             ctx, root_id, &variants, |variant| &variant.identifier, "enum variant"
         )?;
         self.check_poly_args_collision(ctx, root_id, &definition.poly_vars)?;
         // Note: although we cannot have embedded type dependent on the
         // polymorphic variables, they might still be present as tokens
         let definition_id = definition.this.upcast();
         self.lookup.insert(definition_id, DefinedType {
             ast_root: root_id,
             ast_definition: definition_id,
             definition: DefinedTypeVariant::Enum(EnumType{
                 variants,
                 representation: Self::enum_tag_type(min_enum_value, max_enum_value)
             }),
             poly_vars: self.create_initial_poly_vars(&definition.poly_vars),
             is_polymorph: false,
             is_pointerlike: false,
             monomorphs: Vec::new()
         });
         Ok(true)
+    }
     /// Resolves the basic union definiton to an entry in the type table. It
     /// will not instantiate any monomorphized instances of polymorphic union
     /// definitions. If a subtype has to be resolved first then this function
     /// will return `false` after calling `ingest_resolve_result`.
     fn resolve_base_union_definition(&mut self, ctx: &mut TypeCtx, root_id: RootId, definition_id: DefinitionId) -> Result<bool, ParseError> {
         debug_assert!(ctx.heap[definition_id].is_union());
         debug_assert!(!self.lookup.contains_key(&definition_id), "base union already resolved");
         let definition = ctx.heap[definition_id].as_union();
         // Make sure all embedded types are resolved
         for variant in &definition.variants {
             match &variant.value {
                 UnionVariantValue::None => {},
                 UnionVariantValue::Embedded(embedded) => {
                     for embedded_id in embedded {
                         let resolve_result = self.resolve_base_parser_type(ctx, &definition.poly_vars, root_id, *embedded_id)?;
                         if !self.ingest_resolve_result(ctx, resolve_result)? {
                             return Ok(false)
+                        }
+                    }
+                }
+            }
+        }
         // If here then all embedded types are resolved
         // Determine the union variants
         let mut tag_value = -1;
         let mut variants = Vec::with_capacity(definition.variants.len());
         for variant in &definition.variants {
             tag_value += 1;
             let embedded = match &variant.value {
                 UnionVariantValue::None => { Vec::new() },
                 UnionVariantValue::Embedded(embedded) => {
                     // Type should be resolvable, we checked this above
                     embedded.clone()
                 },
             };
             variants.push(UnionVariant{
                 identifier: variant.identifier.clone(),
                 embedded,
                 tag_value,
             })
+        }
         // Ensure union names and polymorphic args do not conflict
         self.check_identifier_collision(
-            ctx, root_id, &variants, |variant| &variant.identifier, "enum variant"
+            ctx, root_id, &variants, |variant| &variant.identifier, "union variant"
         )?;
         self.check_poly_args_collision(ctx, root_id, &definition.poly_vars)?;
         let mut poly_args = self.create_initial_poly_vars(&definition.poly_vars);
         for variant in &variants {
             for embedded_id in &variant.embedded {
                 self.check_and_resolve_embedded_type_and_modify_poly_args(ctx, definition_id, &mut poly_args, root_id, *embedded_id)?;
+            }
+        }
         let is_polymorph = poly_args.iter().any(|arg| arg.is_in_use);
         // Insert base definition in type table
         self.lookup.insert(definition_id, DefinedType {
             ast_root: root_id,
             ast_definition: definition_id,
             definition: DefinedTypeVariant::Union(UnionType{
                 variants,
                 tag_representation: Self::enum_tag_type(-1, tag_value),
             }),
             poly_vars: poly_args,
             is_polymorph,
             is_pointerlike: false, // TODO: @cyclic_types
             monomorphs: Vec::new()
         });
         Ok(true)
+    }
     /// Resolves the basic struct definition to an entry in the type table. It
     /// will not instantiate any monomorphized instances of polymorphic struct
     /// definitions.
     fn resolve_base_struct_definition(&mut self, ctx: &mut TypeCtx, root_id: RootId, definition_id: DefinitionId) -> Result<bool, ParseError> {
         debug_assert!(ctx.heap[definition_id].is_struct());
         debug_assert!(!self.lookup.contains_key(&definition_id), "base struct already resolved");
         let definition = ctx.heap[definition_id].as_struct();
         // Make sure all fields point to resolvable types
         for field_definition in &definition.fields {
             let resolve_result = self.resolve_base_parser_type(ctx, &definition.poly_vars, root_id, field_definition.parser_type)?;
             if !self.ingest_resolve_result(ctx, resolve_result)? {
                 return Ok(false)
+            }
+        }
         // All fields types are resolved, construct base type
         let mut fields = Vec::with_capacity(definition.fields.len());
         for field_definition in &definition.fields {
             fields.push(StructField{
                 identifier: field_definition.field.clone(),
                 parser_type: field_definition.parser_type,
             })
+        }
         // And make sure no conflicts exist in field names and/or polymorphic args
         self.check_identifier_collision(
             ctx, root_id, &fields, |field| &field.identifier, "struct field"
         )?;
         self.check_poly_args_collision(ctx, root_id, &definition.poly_vars)?;
         // Construct representation of polymorphic arguments
         let mut poly_args = self.create_initial_poly_vars(&definition.poly_vars);
         for field in &fields {
             self.check_and_resolve_embedded_type_and_modify_poly_args(ctx, definition_id, &mut poly_args, root_id, field.parser_type)?;
+        }
         let is_polymorph = poly_args.iter().any(|arg| arg.is_in_use);
         self.lookup.insert(definition_id, DefinedType{
             ast_root: root_id,
             ast_definition: definition_id,
             definition: DefinedTypeVariant::Struct(StructType{
                 fields,
             }),
             poly_vars: poly_args,
             is_polymorph,
             is_pointerlike: false, // TODO: @cyclic
             monomorphs: Vec::new(),
         });
         Ok(true)
+    }
     /// Resolves the basic function definition to an entry in the type table. It
     /// will not instantiate any monomorphized instances of polymorphic function
     /// definitions.
     fn resolve_base_function_definition(&mut self, ctx: &mut TypeCtx, root_id: RootId, definition_id: DefinitionId) -> Result<bool, ParseError> {
         debug_assert!(ctx.heap[definition_id].is_function());
         debug_assert!(!self.lookup.contains_key(&definition_id), "base function already resolved");
         let definition = ctx.heap[definition_id].as_function();
         let return_type = definition.return_type;
         // Check the return type
         let resolve_result = self.resolve_base_parser_type(
             ctx, &definition.poly_vars, root_id, definition.return_type
         )?;
         if !self.ingest_resolve_result(ctx, resolve_result)? {
             return Ok(false)
+        }
         // Check the argument types
         for param_id in &definition.parameters {
             let param = &ctx.heap[*param_id];
             let resolve_result = self.resolve_base_parser_type(
                 ctx, &definition.poly_vars, root_id, param.parser_type
             )?;
             if !self.ingest_resolve_result(ctx, resolve_result)? {
                 return Ok(false)
+            }
+        }
         // Construct arguments to function
         let mut arguments = Vec::with_capacity(definition.parameters.len());
         for param_id in &definition.parameters {
             let param = &ctx.heap[*param_id];
             arguments.push(FunctionArgument{
                 identifier: param.identifier.clone(),
                 parser_type: param.parser_type,
             })
+        }
         // Check conflict of argument and polyarg identifiers
         self.check_identifier_collision(
             ctx, root_id, &arguments, |arg| &arg.identifier, "function argument"
         )?;
         self.check_poly_args_collision(ctx, root_id, &definition.poly_vars)?;
         // Construct polymorphic arguments
         let mut poly_args = self.create_initial_poly_vars(&definition.poly_vars);
         let return_type_id = definition.return_type;
         self.check_and_resolve_embedded_type_and_modify_poly_args(ctx, definition_id, &mut poly_args, root_id, return_type_id)?;
         for argument in &arguments {
             self.check_and_resolve_embedded_type_and_modify_poly_args(ctx, definition_id, &mut poly_args, root_id, argument.parser_type)?;
+        }
         let is_polymorph = poly_args.iter().any(|arg| arg.is_in_use);
         // Construct entry in type table
         self.lookup.insert(definition_id, DefinedType{
             ast_root: root_id,
             ast_definition: definition_id,
             definition: DefinedTypeVariant::Function(FunctionType{
                 return_type,
                 arguments,
             }),
             poly_vars: poly_args,
             is_polymorph,
             is_pointerlike: false, // TODO: @cyclic
             monomorphs: Vec::new(),
         });
         Ok(true)
+    }
     /// Resolves the basic component definition to an entry in the type table.
     /// It will not instantiate any monomorphized instancees of polymorphic
     /// component definitions.
     fn resolve_base_component_definition(&mut self, ctx: &mut TypeCtx, root_id: RootId, definition_id: DefinitionId) -> Result<bool, ParseError> {
         debug_assert!(ctx.heap[definition_id].is_component());
         debug_assert!(!self.lookup.contains_key(&definition_id), "base component already resolved");
         let definition = ctx.heap[definition_id].as_component();
         let component_variant = definition.variant;
         // Check argument types
         for param_id in &definition.parameters {
             let param = &ctx.heap[*param_id];
             let resolve_result = self.resolve_base_parser_type(
                 ctx, &definition.poly_vars, root_id, param.parser_type
             )?;
             if !self.ingest_resolve_result(ctx, resolve_result)? {
                 return Ok(false)
+            }
+        }
         // Construct argument types
         let mut arguments = Vec::with_capacity(definition.parameters.len());
         for param_id in &definition.parameters {
             let param = &ctx.heap[*param_id];
             arguments.push(FunctionArgument{
                 identifier: param.identifier.clone(),
                 parser_type: param.parser_type
             })
+        }
         // Check conflict of argument and polyarg identifiers
         self.check_identifier_collision(
             ctx, root_id, &arguments, |arg| &arg.identifier, "component argument"
         )?;
         self.check_poly_args_collision(ctx, root_id, &definition.poly_vars)?;
         // Construct polymorphic arguments
         let mut poly_args = self.create_initial_poly_vars(&definition.poly_vars);
         for argument in &arguments {
             self.check_and_resolve_embedded_type_and_modify_poly_args(ctx, definition_id, &mut poly_args, root_id, argument.parser_type)?;
+        }
         let is_polymorph = poly_args.iter().any(|v| v.is_in_use);
         // Construct entry in type table
         self.lookup.insert(definition_id, DefinedType{
             ast_root: root_id,
             ast_definition: definition_id,
             definition: DefinedTypeVariant::Component(ComponentType{
                 variant: component_variant,
                 arguments,
             }),
             poly_vars: poly_args,
             is_polymorph,
             is_pointerlike: false, // TODO: @cyclic
             monomorphs: Vec::new(),
         });
         Ok(true)
+    }
     /// Takes a ResolveResult and returns `true` if the caller can happily
     /// continue resolving its current type, or `false` if the caller must break
     /// resolving the current type and exit to the outer resolving loop. In the
     /// latter case the `result` value was `ResolveResult::Unresolved`, implying
     /// that the type must be resolved first.
     fn ingest_resolve_result(&mut self, ctx: &TypeCtx, result: ResolveResult) -> Result<bool, ParseError> {
         match result {
             ResolveResult::BuiltIn | ResolveResult::PolyArg(_) => Ok(true),
             ResolveResult::Resolved(_) => Ok(true),
             ResolveResult::Unresolved((root_id, definition_id)) => {
                 if self.iter.contains(root_id, definition_id) {
                     // Cyclic dependency encountered
                     // TODO: Allow this
                     let mut error = ParseError::new_error(
                         &ctx.modules[root_id.index as usize].source, ctx.heap[definition_id].position(),
                         "Evaluating this type definition results in a cyclic type"
                     );
                     for (breadcrumb_idx, (root_id, definition_id)) in self.iter.breadcrumbs.iter().enumerate() {
                         let msg = if breadcrumb_idx == 0 {
                             "The cycle started with this definition"
                         } else {
                             "Which depends on this definition"
                         };
                         error = error.with_postfixed_info(
                             &ctx.modules[root_id.index as usize].source,
                             ctx.heap[*definition_id].position(), msg
                         );
+                    }
                     Err(error)
                 } else {
                     // Type is not yet resolved, so push IDs on iterator and
                     // continue the resolving loop
                     self.iter.push(root_id, definition_id);
                     Ok(false)
+                }
+            }
+        }
+    }
     /// Each type definition may consist of several embedded subtypes. This
     /// function checks whether that embedded type is a builtin, a direct
     /// reference to a polymorphic argument, or an (un)resolved type definition.
     /// If the embedded type's symbol cannot be found then this function returns
     /// an error.
     ///
     /// If the embedded type is resolved, then one always receives the type's
     /// (module, definition) tuple. If any of the types in the embedded type's
     /// tree is not yet resolved, then one may receive a (module, definition)
     /// tuple that does not correspond to the `parser_type_id` passed into this
     /// function.
     fn resolve_base_parser_type(&mut self, ctx: &TypeCtx, poly_vars: &Vec<Identifier>, root_id: RootId, parser_type_id: ParserTypeId) -> Result<ResolveResult, ParseError> {
         use ParserTypeVariant as PTV;
         // Prepping iterator
         self.parser_type_iter.clear();
         self.parser_type_iter.push_back(parser_type_id);
         // Result for the very first time we resolve a
         let mut resolve_result = None;
         let mut set_resolve_result = |v: ResolveResult| {
             if resolve_result.is_none() { resolve_result = Some(v); }
         };
         'resolve_loop: while let Some(parser_type_id) = self.parser_type_iter.pop_back() {
             let parser_type = &ctx.heap[parser_type_id];
             match &parser_type.variant {
                 // Builtin types. An array is a builtin as it is implemented as a
                 // couple of pointers, so we do not require the subtype to be fully
                 // resolved. Similar for input/output ports.
                 PTV::Array(_) | PTV::Input(_) | PTV::Output(_) | PTV::Message |
                 PTV::Bool | PTV::Byte | PTV::Short | PTV::Int | PTV::Long |
                 PTV::String => {
                     set_resolve_result(ResolveResult::BuiltIn);
                 },
                 // IntegerLiteral types and the inferred marker are not allowed in
                 // definitions of types
                 PTV::IntegerLiteral |
                 PTV::Inferred => {
                     debug_assert!(false, "Encountered illegal ParserTypeVariant within type definition");
                     unreachable!();
                 },
                 // Symbolic type, make sure its base type, and the base types
                 // of all members of the embedded type tree are resolved. We
                 // don't care about monomorphs yet.
                 PTV::Symbolic(symbolic) => {
                     // Check if the symbolic type is one of the definition's
                     // polymorphic arguments. If so then we can halt the
                     // execution
                     for (poly_arg_idx, poly_arg) in poly_vars.iter().enumerate() {
                         if symbolic.identifier.matches_identifier(poly_arg) {
                             set_resolve_result(ResolveResult::PolyArg(poly_arg_idx));
                             continue 'resolve_loop;
+                        }
+                    }
                     // Lookup the definition in the symbol table
                     let (symbol, mut ident_iter) = ctx.symbols.resolve_namespaced_identifier(root_id, &symbolic.identifier);
                     if symbol.is_none() {
                         return Err(ParseError::new_error(
                             &ctx.modules[root_id.index as usize].source, symbolic.identifier.position,
                             "Could not resolve type"
                         ))
+                    }
                     let symbol_value = symbol.unwrap();
                     let module_source = &ctx.modules[root_id.index as usize].source;
                     match symbol_value.symbol {
                         Symbol::Namespace(_) => {
                             // Reference to a namespace instead of a type
                             let last_ident = ident_iter.prev();
                             return if ident_iter.num_remaining() == 0 {
                                 // Could also have polymorphic args, but we
                                 // don't care, just throw this error:
                                 Err(ParseError::new_error(
                                     module_source, symbolic.identifier.position,
                                     "Expected a type, got a module name"
                                 ))
                             } else if last_ident.is_some() && last_ident.map(|(_, poly_args)| poly_args.is_some()).unwrap() {
                                 // Halted at a namespaced because we encountered
                                 // polymorphic arguments
                                 Err(ParseError::new_error(
                                     module_source, symbolic.identifier.position,
                                     "Illegal specification of polymorphic arguments to a module name"
                                 ))
                             } else {
                                 // Impossible (with the current implementation
                                 // of the symbol table)
                                 unreachable!(
                                     "Got namespace symbol with {} returned symbols from {}",
                                     ident_iter.num_returned(),
                                     &String::from_utf8_lossy(&symbolic.identifier.value)
                                 );
+                            }
                         },
                         Symbol::Definition((root_id, definition_id)) => {
                             let definition = &ctx.heap[definition_id];
                             if ident_iter.num_remaining() > 0 {
                                 // Namespaced identifier is longer than the type
                                 // we found. Return the appropriate message
                                 return if definition.is_struct() || definition.is_enum() {
                                     Err(ParseError::new_error(
                                         module_source, symbolic.identifier.position,
                                         &format!(
                                             "Unknown type '{}', did you mean to use '{}'?",
                                             String::from_utf8_lossy(&symbolic.identifier.value),
                                             String::from_utf8_lossy(&definition.identifier().value)
+                                        )
                                     ))
                                 } else {
                                     Err(ParseError::new_error(
                                         module_source, symbolic.identifier.position,
                                         "Unknown datatype"
                                     ))
+                                }
+                            }
                             // Found a match, make sure it is a datatype
                             if !(definition.is_struct() || definition.is_enum()) {
+                            if !(definition.is_struct() || definition.is_enum() || definition.is_union()) {
                                 return Err(ParseError::new_error(
                                     module_source, symbolic.identifier.position,
                                     "Embedded types must be datatypes (structs or enums)"
                                 ))
+                            }
                             // Found a struct/enum definition
                             if !self.lookup.contains_key(&definition_id) {
                                 // Type is not yet resoled, immediately return
                                 // this
                                 return Ok(ResolveResult::Unresolved((root_id, definition_id)));
+                            }
                             // Type is resolved, so set as result, but continue
                             // iterating over the parser types in the embedded
                             // type's tree
                             set_resolve_result(ResolveResult::Resolved((root_id, definition_id)));
                             // Note: because we're resolving parser types, not
                             // embedded types, we're parsing a tree, so we can't
                             // get stuck in a cyclic loop.
                             let last_ident = ident_iter.prev();
                             if let Some((_, Some(poly_args))) = last_ident {
                                 for poly_arg_type_id in poly_args {
                                     self.parser_type_iter.push_back(*poly_arg_type_id);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
         // If here then all types in the embedded type's tree were resolved.
         debug_assert!(resolve_result.is_some(), "faulty logic in ParserType resolver");
         return Ok(resolve_result.unwrap())
+    }
     fn create_initial_poly_vars(&self, poly_args: &[Identifier]) -> Vec<PolyVar> {
         poly_args
             .iter()
             .map(|v| PolyVar{ identifier: v.clone(), is_in_use: false })
             .collect()
+    }
     /// This function modifies the passed `poly_args` by checking the embedded
     /// type tree. This should be called after `resolve_base_parser_type` is
     /// called on each node in this tree: we assume that each symbolic type was
     /// resolved to either a polymorphic arg or a definition.
     ///
     /// This function will also make sure that if the embedded type has
     /// polymorphic variables itself, that the number of polymorphic variables
     /// matches the number of arguments in the associated definition.
     ///
     /// Finally, for all embedded types (which includes function/component
     /// arguments and return types) in type definitions we will modify the AST
     /// when the embedded type is a polymorphic variable or points to another
     /// user-defined type.
     fn check_and_resolve_embedded_type_and_modify_poly_args(
         &mut self, ctx: &mut TypeCtx,
         type_definition_id: DefinitionId, poly_args: &mut [PolyVar],
         root_id: RootId, embedded_type_id: ParserTypeId,
     ) -> Result<(), ParseError> {
         use ParserTypeVariant as PTV;
         self.parser_type_iter.clear();
         self.parser_type_iter.push_back(embedded_type_id);
         'type_loop: while let Some(embedded_type_id) = self.parser_type_iter.pop_back() {
             let embedded_type = &mut ctx.heap[embedded_type_id];
             match &mut embedded_type.variant {
                 PTV::Message | PTV::Bool |
                 PTV::Byte | PTV::Short | PTV::Int | PTV::Long |
                 PTV::String => {
                     // Builtins, no modification/iteration required
                 },
                 PTV::IntegerLiteral | PTV::Inferred => {
                     // TODO: @hack Allowed for now so we can continue testing
                     //  the parser/lexer
                     // debug_assert!(false, "encountered illegal parser type during ParserType/PolyArg modification");
                     // unreachable!();
                 },
                 PTV::Array(subtype_id) |
                 PTV::Input(subtype_id) |
                 PTV::Output(subtype_id) => {
                     // Outer type is fixed, but inner type might be symbolic
                     self.parser_type_iter.push_back(*subtype_id);
                 },
                 PTV::Symbolic(symbolic) => {
                     for (poly_arg_idx, poly_arg) in poly_args.iter_mut().enumerate() {
                         if symbolic.identifier.matches_identifier(&poly_arg.identifier) {
                             poly_arg.is_in_use = true;
                             // TODO: If we allow higher-kinded types in the future,
                             //  then we can't continue here, but must resolve the
                             //  polyargs as well
                             debug_assert!(symbolic.identifier.get_poly_args().is_none(), "got polymorphic arguments to a polymorphic variable");
                             debug_assert!(symbolic.variant.is_none(), "symbolic parser type's variant already resolved");
                             symbolic.variant = Some(SymbolicParserTypeVariant::PolyArg(type_definition_id, poly_arg_idx));
                             continue 'type_loop;
+                        }
+                    }
                     // Must match a definition
                     let (symbol, ident_iter) = ctx.symbols.resolve_namespaced_identifier(root_id, &symbolic.identifier);
                     debug_assert!(symbol.is_some(), "could not resolve symbolic parser type when determining poly args");
                     let symbol = symbol.unwrap();
                     debug_assert_eq!(ident_iter.num_remaining(), 0, "no exact symbol match when determining poly args");
                     let (_root_id, definition_id) = symbol.as_definition().unwrap();
                     // Must be a struct, enum, or union, we checked this
                     let defined_type = self.lookup.get(&definition_id).unwrap();
                     let (_, poly_args) = ident_iter.prev().unwrap();
                     let poly_args = poly_args.unwrap_or_default();
                     if cfg!(debug_assertions) {
                         // Everything here should already be checked in
                         // `resolve_base_parser_type`.
                         let type_class = defined_type.definition.type_class();
                         debug_assert!(
                             type_class == TypeClass::Struct || type_class == TypeClass::Enum || type_class == TypeClass::Union,
                             "embedded type's class is not struct, enum or union"
                         );
                         debug_assert_eq!(poly_args.len(), symbolic.identifier.poly_args.len());
+                    }
                     if poly_args.len() != defined_type.poly_vars.len() {
                         // Mismatch in number of polymorphic arguments. This is
                         // not allowed in type definitions (no inference is
                         // allowed within type definitions, only in bodies of
                         // functions/components).
                         let module_source = &ctx.modules[root_id.index as usize].source;
                         let number_args_msg = if defined_type.poly_vars.is_empty() {
                             String::from("is not polymorphic")
                         } else {
                             format!("accepts {} polymorphic arguments", defined_type.poly_vars.len())
                         };
                         return Err(ParseError::new_error(
                             module_source, symbolic.identifier.position,
                             &format!(
                                 "The type '{}' {}, but {} polymorphic arguments were provided",
                                 String::from_utf8_lossy(&symbolic.identifier.strip_poly_args()),
                                 number_args_msg, poly_args.len()
+                            )
                         ));
+                    }
                     self.parser_type_iter.extend(poly_args);
                     debug_assert!(symbolic.variant.is_none(), "symbolic parser type's variant already resolved");
                     symbolic.variant = Some(SymbolicParserTypeVariant::Definition(definition_id));
+                }
+            }
+        }
         // All nodes in the embedded type tree were valid
         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>(
         &self, ctx: &TypeCtx, 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 = &ctx.modules[root_id.index as usize].source;
                     return Err(ParseError::new_error(
                         module_source, item_ident.position, &format!("This {} is defined more than once", item_name)
                     ).with_postfixed_info(
                         module_source, other_item_ident.position, &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(
         &self, ctx: &TypeCtx, 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 = &ctx.modules[root_id.index as usize].source;
                     return Err(ParseError::new_error(
                         module_source, poly_arg.position,
                         "This polymorphic argument is defined more than once"
                     ).with_postfixed_info(
                         module_source, other_poly_arg.position,
                         "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.resolve_symbol(root_id, &poly_arg.value) {
                 // We have a conflict
                 let module_source = &ctx.modules[root_id.index as usize].source;
                 return Err(ParseError::new_error(
                     module_source, poly_arg.position,
                     "This polymorphic argument conflicts with another symbol"
                 ).with_postfixed_info(
                     module_source, symbol.position,
                     "It conflicts due to this symbol"
                 ));
+            }
+        }
         // All arguments are fine
         Ok(())
+    }
     //--------------------------------------------------------------------------
     // Small utilities
     //--------------------------------------------------------------------------
     fn enum_tag_type(min_tag_value: i64, max_tag_value: i64) -> PrimitiveType {
         // TODO: @consistency tag values should be handled correctly
         debug_assert!(min_tag_value <= max_tag_value);
         let abs_max_value = min_tag_value.abs().max(max_tag_value.abs());
         if abs_max_value <= u8::max_value() as i64 {
             PrimitiveType::Byte
         } else if abs_max_value <= u16::max_value() as i64 {
             PrimitiveType::Short
         } else if abs_max_value <= u32::max_value() as i64 {
             PrimitiveType::Int
         } else {
             PrimitiveType::Long
+        }
+    }
     fn find_root_id(ctx: &TypeCtx, definition_id: DefinitionId) -> RootId {
         // TODO: Keep in lookup or something
         for module in ctx.modules {
             let root_id = module.root_id;
             let root = &ctx.heap[root_id];
             for module_definition_id in root.definitions.iter() {
                 if *module_definition_id == definition_id {
                     return root_id
+                }
+            }
+        }
         debug_assert!(false, "DefinitionId without corresponding RootId");
         unreachable!();
+    }
+}
@@ \ No newline at end of file @@

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