CSY/reowolf Changeset - 3381d0627372 · Centrum Wiskunde & Informatica (CWI)

Changeset - 3381d0627372

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0 4 1

MH - 4 years ago 2021-03-26 09:02:38
henger@cwi.nl

WIP on struct field access inference

2 files changed:

src/protocol/lexer.rs

src/protocol/parser/type_resolver.rs

445

171

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src/protocol/lexer.rs

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 use crate::protocol::ast::*;
 use crate::protocol::inputsource::*;
 const MAX_LEVEL: usize = 128;
 const MAX_NAMESPACES: u8 = 8; // only three levels are supported at the moment
 fn is_vchar(x: Option<u8>) -> bool {
     if let Some(c) = x {
         c >= 0x21 && c <= 0x7E
     } else {
         false
+    }
+}
 fn is_wsp(x: Option<u8>) -> bool {
     if let Some(c) = x {
         c == b' ' || c == b'\t'
     } else {
         false
+    }
+}
 fn is_ident_start(x: Option<u8>) -> bool {
     if let Some(c) = x {
         c >= b'A' && c <= b'Z' || c >= b'a' && c <= b'z'
     } else {
         false
+    }
+}
 fn is_ident_rest(x: Option<u8>) -> bool {
     if let Some(c) = x {
         c >= b'A' && c <= b'Z' || c >= b'a' && c <= b'z' || c >= b'0' && c <= b'9' || c == b'_'
     } else {
         false
+    }
+}
 fn is_constant(x: Option<u8>) -> bool {
     if let Some(c) = x {
         c >= b'0' && c <= b'9' || c == b'\''
     } else {
         false
+    }
+}
 fn is_integer_start(x: Option<u8>) -> bool {
     if let Some(c) = x {
         c >= b'0' && c <= b'9'
     } else {
         false
+    }
+}
 fn is_integer_rest(x: Option<u8>) -> bool {
     if let Some(c) = x {
         c >= b'0' && c <= b'9'
             || c >= b'a' && c <= b'f'
             || c >= b'A' && c <= b'F'
             || c == b'x'
             || c == b'o'
     } else {
         false
+    }
+}
 fn lowercase(x: u8) -> u8 {
     if x >= b'A' && x <= b'Z' {
         x - b'A' + b'a'
     } else {
+        x
+    }
+}
 pub struct Lexer<'a> {
     source: &'a mut InputSource,
     level: usize,
+}
 impl Lexer<'_> {
     pub fn new(source: &mut InputSource) -> Lexer {
         Lexer { source, level: 0 }
+    }
     fn error_at_pos(&self, msg: &str) -> ParseError2 {
         ParseError2::new_error(self.source, self.source.pos(), msg)
+    }
     fn consume_line(&mut self) -> Result<Vec<u8>, ParseError2> {
         let mut result: Vec<u8> = Vec::new();
         let mut next = self.source.next();
         while next.is_some() && next != Some(b'\n') && next != Some(b'\r') {
             if !(is_vchar(next) || is_wsp(next)) {
                 return Err(self.error_at_pos("Expected visible character or whitespace"));
+            }
             result.push(next.unwrap());
             self.source.consume();
             next = self.source.next();
+        }
         if next.is_some() {
             self.source.consume();
+        }
         if next == Some(b'\r') && self.source.next() == Some(b'\n') {
             self.source.consume();
+        }
         Ok(result)
+    }
     fn consume_whitespace(&mut self, expected: bool) -> Result<(), ParseError2> {
         let mut found = false;
         let mut next = self.source.next();
         while next.is_some() {
             if next == Some(b' ')
                 || next == Some(b'\t')
                 || next == Some(b'\r')
                 || next == Some(b'\n')
+            {
                 self.source.consume();
                 next = self.source.next();
                 found = true;
                 continue;
+            }
             if next == Some(b'/') {
                 next = self.source.lookahead(1);
                 if next == Some(b'/') {
                     self.source.consume(); // slash
                     self.source.consume(); // slash
                     self.consume_line()?;
                     next = self.source.next();
                     found = true;
                     continue;
+                }
                 if next == Some(b'*') {
                     self.source.consume(); // slash
                     self.source.consume(); // star
                     next = self.source.next();
                     while next.is_some() {
                         if next == Some(b'*') {
                             next = self.source.lookahead(1);
                             if next == Some(b'/') {
                                 self.source.consume(); // star
                                 self.source.consume(); // slash
                                 break;
+                            }
+                        }
                         self.source.consume();
                         next = self.source.next();
+                    }
                     next = self.source.next();
                     found = true;
                     continue;
+                }
+            }
             break;
+        }
         if expected && !found {
             Err(self.error_at_pos("Expected whitespace"))
         } else {
             Ok(())
+        }
+    }
     fn consume_any_chars(&mut self) {
         if !is_ident_start(self.source.next()) { return }
         self.source.consume();
         while is_ident_rest(self.source.next()) {
             self.source.consume()
+        }
+    }
     fn has_keyword(&self, keyword: &[u8]) -> bool {
         if !self.source.has(keyword) {
             return false;
+        }
         // Word boundary
         if let Some(next) = self.source.lookahead(keyword.len()) {
             !(next >= b'A' && next <= b'Z' || next >= b'a' && next <= b'z')
         } else {
             true
+        }
+    }
     fn consume_keyword(&mut self, keyword: &[u8]) -> Result<(), ParseError2> {
         let len = keyword.len();
         for i in 0..len {
             let expected = Some(lowercase(keyword[i]));
             let next = self.source.next();
             if next != expected {
                 return Err(self.error_at_pos(&format!("Expected keyword '{}'", String::from_utf8_lossy(keyword))));
+            }
             self.source.consume();
+        }
         if let Some(next) = self.source.next() {
             if next >= b'A' && next <= b'Z' || next >= b'a' && next <= b'z' || next >= b'0' && next <= b'9' {
                 return Err(self.error_at_pos(&format!("Expected word boundary after '{}'", String::from_utf8_lossy(keyword))));
+            }
+        }
         Ok(())
+    }
     fn has_string(&self, string: &[u8]) -> bool {
         self.source.has(string)
+    }
     fn consume_string(&mut self, string: &[u8]) -> Result<(), ParseError2> {
         let len = string.len();
         for i in 0..len {
             let expected = Some(string[i]);
             let next = self.source.next();
             if next != expected {
                 return Err(self.error_at_pos(&format!("Expected {}", String::from_utf8_lossy(string))));
+            }
             self.source.consume();
+        }
         Ok(())
+    }
     /// Generic comma-separated consumer. If opening delimiter is not found then
     /// `Ok(None)` will be returned. Otherwise will consume the comma separated
     /// values, allowing a trailing comma. If no comma is found and the closing
     /// delimiter is not found, then a parse error with `expected_end_msg` is
     /// returned.
     fn consume_comma_separated<T, F>(
         &mut self, h: &mut Heap, open: u8, close: u8, expected_end_msg: &str, func: F
     ) -> Result<Option<Vec<T>>, ParseError2>
         where F: Fn(&mut Lexer, &mut Heap) -> Result<T, ParseError2>
+    {
         if Some(open) != self.source.next() {
             return Ok(None)
+        }
         self.source.consume();
         self.consume_whitespace(false)?;
         let mut elements = Vec::new();
         let mut had_comma = true;
         loop {
             if Some(close) == self.source.next() {
                 self.source.consume();
                 break;
             } else if !had_comma {
                 return Err(ParseError2::new_error(
                     &self.source, self.source.pos(), expected_end_msg
                 ));
+            }
             elements.push(func(self, h)?);
             self.consume_whitespace(false)?;
             had_comma = self.source.next() == Some(b',');
             if had_comma {
                 self.source.consume();
                 self.consume_whitespace(false)?;
+            }
+        }
         Ok(Some(elements))
+    }
     /// Essentially the same as `consume_comma_separated`, but will not allocate
     /// memory. Will return `true` and leave the input position at the end of
     /// the comma-separated list if well formed. Otherwise returns `false` and
     /// leaves the input position at a "random" position.
     fn consume_comma_separated_spilled_without_pos_recovery<F: Fn(&mut Lexer) -> bool>(
         &mut self, open: u8, close: u8, func: F
     ) -> bool {
         if Some(open) != self.source.next() {
             return true;
+        }
         self.source.consume();
         if self.consume_whitespace(false).is_err() { return false };
         let mut had_comma = true;
         loop {
             if Some(close) == self.source.next() {
                 self.source.consume();
                 return true;
             } else if !had_comma {
                 return false;
+            }
             if !func(self) { return false; }
             if self.consume_whitespace(false).is_err() { return false };
             had_comma = self.source.next() == Some(b',');
             if had_comma {
                 self.source.consume();
                 if self.consume_whitespace(false).is_err() { return false; }
+            }
+        }
+    }
     fn consume_ident(&mut self) -> Result<Vec<u8>, ParseError2> {
         if !self.has_identifier() {
             return Err(self.error_at_pos("Expected identifier"));
+        }
         let mut result = Vec::new();
         let mut next = self.source.next();
         result.push(next.unwrap());
         self.source.consume();
         next = self.source.next();
         while is_ident_rest(next) {
             result.push(next.unwrap());
             self.source.consume();
             next = self.source.next();
+        }
         Ok(result)
+    }
     fn has_integer(&mut self) -> bool {
         is_integer_start(self.source.next())
+    }
     fn consume_integer(&mut self) -> Result<i64, ParseError2> {
         let position = self.source.pos();
         let mut data = Vec::new();
         let mut next = self.source.next();
         while is_integer_rest(next) {
             data.push(next.unwrap());
             self.source.consume();
             next = self.source.next();
+        }
         let data_len = data.len();
         debug_assert_ne!(data_len, 0);
         if data_len == 1 {
             debug_assert!(data[0] >= b'0' && data[0] <= b'9');
             return Ok((data[0] - b'0') as i64);
         } else {
             // TODO: Fix, u64 should be supported as well
             let parsed = if data[1] == b'b' {
                 let data = String::from_utf8_lossy(&data[2..]);
                 i64::from_str_radix(&data, 2)
             } else if data[1] == b'o' {
                 let data = String::from_utf8_lossy(&data[2..]);
                 i64::from_str_radix(&data, 8)
             } else if data[1] == b'x' {
                 let data = String::from_utf8_lossy(&data[2..]);
                 i64::from_str_radix(&data, 16)
             } else {
                 // Assume decimal
                 let data = String::from_utf8_lossy(&data);
                 i64::from_str_radix(&data, 10)
             };
             if let Err(_err) = parsed {
                 return Err(ParseError2::new_error(&self.source, position, "Invalid integer constant"));
+            }
             Ok(parsed.unwrap())
+        }
+    }
     // Statement keywords
     // TODO: Clean up these functions
     fn has_statement_keyword(&self) -> bool {
         self.has_keyword(b"channel")
             || self.has_keyword(b"skip")
             || self.has_keyword(b"if")
             || self.has_keyword(b"while")
             || self.has_keyword(b"break")
             || self.has_keyword(b"continue")
             || self.has_keyword(b"synchronous")
             || self.has_keyword(b"return")
             || self.has_keyword(b"assert")
             || self.has_keyword(b"goto")
             || self.has_keyword(b"new")
+    }
     fn has_type_keyword(&self) -> bool {
         self.has_keyword(b"in")
             || self.has_keyword(b"out")
             || self.has_keyword(b"msg")
             || self.has_keyword(b"boolean")
             || self.has_keyword(b"byte")
             || self.has_keyword(b"short")
             || self.has_keyword(b"int")
             || self.has_keyword(b"long")
             || self.has_keyword(b"auto")
+    }
     fn has_builtin_keyword(&self) -> bool {
         self.has_keyword(b"get")
             || self.has_keyword(b"fires")
             || self.has_keyword(b"create")
             || self.has_keyword(b"length")
+    }
     fn has_reserved(&self) -> bool {
         self.has_statement_keyword()
             || self.has_type_keyword()
             || self.has_builtin_keyword()
             || self.has_keyword(b"let")
             || self.has_keyword(b"struct")
             || self.has_keyword(b"enum")
             || self.has_keyword(b"true")
             || self.has_keyword(b"false")
             || self.has_keyword(b"null")
+    }
     // Identifiers
     fn has_identifier(&self) -> bool {
         if self.has_statement_keyword() || self.has_type_keyword() || self.has_builtin_keyword() {
             return false;
+        }
         let next = self.source.next();
         is_ident_start(next)
+    }
     fn consume_identifier(&mut self) -> Result<Identifier, ParseError2> {
         if self.has_statement_keyword() || self.has_type_keyword() || self.has_builtin_keyword() {
             return Err(self.error_at_pos("Expected identifier"));
+        }
         let position = self.source.pos();
         let value = self.consume_ident()?;
         Ok(Identifier{ position, value })
+    }
     fn consume_identifier_spilled(&mut self) -> Result<(), ParseError2> {
         if self.has_statement_keyword() || self.has_type_keyword() || self.has_builtin_keyword() {
             return Err(self.error_at_pos("Expected identifier"));
+        }
         self.consume_ident()?;
         Ok(())
+    }
     fn has_namespaced_identifier(&self) -> bool {
         self.has_identifier()
+    }
     fn consume_namespaced_identifier(&mut self) -> Result<NamespacedIdentifier, ParseError2> {
         if self.has_reserved() {
             return Err(self.error_at_pos("Encountered reserved keyword"));
+        }
         let position = self.source.pos();
         let mut ns_ident = self.consume_ident()?;
         let mut num_namespaces = 1;
         while self.has_string(b"::") {
             self.consume_string(b"::");
+            self.consume_string(b"::")?;
             if num_namespaces >= MAX_NAMESPACES {
                 return Err(self.error_at_pos("Too many namespaces in identifier"));
+            }
             let new_ident = self.consume_ident()?;
             ns_ident.extend(b"::");
             ns_ident.extend(new_ident);
             num_namespaces += 1;
+        }
         Ok(NamespacedIdentifier{
             position,
             value: ns_ident,
             num_namespaces,
         })
+    }
     fn consume_namespaced_identifier_spilled(&mut self) -> Result<(), ParseError2> {
         // TODO: @performance
         if self.has_reserved() {
             return Err(self.error_at_pos("Encountered reserved keyword"));
+        }
         self.consume_ident()?;
         while self.has_string(b"::") {
             self.consume_string(b"::")?;
             self.consume_ident()?;
+        }
         Ok(())
+    }
     // Types and type annotations
     /// Consumes a type definition. When called the input position should be at
     /// the type specification. When done the input position will be at the end
     /// of the type specifications (hence may be at whitespace).
     fn consume_type2(&mut self, h: &mut Heap, allow_inference: bool) -> Result<ParserTypeId, ParseError2> {
         // Small helper function to convert in/out polymorphic arguments. Not
         // pretty, but return boolean is true if the error is due to inference
         // not being allowed
         let reduce_port_poly_args = |
             heap: &mut Heap,
             port_pos: &InputPosition,
             args: Vec<ParserTypeId>,
         | -> Result<ParserTypeId, bool> {
             match args.len() {
 => if allow_inference {
                     Ok(heap.alloc_parser_type(|this| ParserType{
                         this,
                         pos: port_pos.clone(),
                         variant: ParserTypeVariant::Inferred
                     }))
                 } else {
                     Err(true)
                 },
 => Ok(args[0]),
                 _ => Err(false)
+            }
         };
         // Consume the type
         let pos = self.source.pos();
         let parser_type_variant = if self.has_keyword(b"msg") {
             self.consume_keyword(b"msg")?;
             ParserTypeVariant::Message
         } else if self.has_keyword(b"boolean") {
             self.consume_keyword(b"boolean")?;
             ParserTypeVariant::Bool
         } else if self.has_keyword(b"byte") {
             self.consume_keyword(b"byte")?;
             ParserTypeVariant::Byte
         } else if self.has_keyword(b"short") {
             self.consume_keyword(b"short")?;
             ParserTypeVariant::Short
         } else if self.has_keyword(b"int") {
             self.consume_keyword(b"int")?;
             ParserTypeVariant::Int
         } else if self.has_keyword(b"long") {
             self.consume_keyword(b"long")?;
             ParserTypeVariant::Long
         } else if self.has_keyword(b"str") {
             self.consume_keyword(b"str")?;
             ParserTypeVariant::String
         } else if self.has_keyword(b"auto") {
             if !allow_inference {
                 return Err(ParseError2::new_error(
                         &self.source, pos,
                         "Type inference is not allowed here"
                 ));
+            }
             self.consume_keyword(b"auto")?;
             ParserTypeVariant::Inferred
         } else if self.has_keyword(b"in") {
             // TODO: @cleanup: not particularly neat to have this special case
             //  where we enforce polyargs in the parser-phase
             self.consume_keyword(b"in")?;
             let poly_args = self.consume_polymorphic_args(h, allow_inference)?;
             let poly_arg = reduce_port_poly_args(h, &pos, poly_args)
                 .map_err(|infer_error|  {
                     let msg = if infer_error {
                         "Type inference is not allowed here"
                     } else {
                         "Type 'in' only allows for 1 polymorphic argument"
                     };
                     ParseError2::new_error(&self.source, pos, msg)
                 })?;
             ParserTypeVariant::Input(poly_arg)
         } else if self.has_keyword(b"out") {
             self.consume_keyword(b"out")?;
             let poly_args = self.consume_polymorphic_args(h, allow_inference)?;
             let poly_arg = reduce_port_poly_args(h, &pos, poly_args)
                 .map_err(|infer_error| {
                     let msg = if infer_error {
                         "Type inference is not allowed here"
                     } else {
                         "Type 'out' only allows for 1 polymorphic argument, but {} were specified"
                     };
                     ParseError2::new_error(&self.source, pos, msg)
                 })?;
             ParserTypeVariant::Output(poly_arg)
         } else {
             // Must be a symbolic type
             let identifier = self.consume_namespaced_identifier()?;
             let poly_args = self.consume_polymorphic_args(h, allow_inference)?;
             ParserTypeVariant::Symbolic(SymbolicParserType{identifier, poly_args, variant: None})
         };
         // If the type was a basic type (not supporting polymorphic type
         // arguments), then we make sure the user did not specify any of them.
         let mut backup_pos = self.source.pos();
         if !parser_type_variant.supports_polymorphic_args() {
             self.consume_whitespace(false)?;
             if let Some(b'<') = self.source.next() {
                 return Err(ParseError2::new_error(
                     &self.source, self.source.pos(),
                     "This type does not allow polymorphic arguments"
                 ));
+            }
             self.source.seek(backup_pos);
+        }
         let mut parser_type_id = h.alloc_parser_type(|this| ParserType{
             this, pos, variant: parser_type_variant
         });
         // If we're dealing with arrays, then we need to wrap the currently
         // parsed type in array types
         self.consume_whitespace(false)?;
         while let Some(b'[') = self.source.next() {
             let pos = self.source.pos();
             self.source.consume();
             self.consume_whitespace(false)?;
             if let Some(b']') = self.source.next() {
                 // Type is wrapped in an array
                 self.source.consume();
                 parser_type_id = h.alloc_parser_type(|this| ParserType{
                     this, pos, variant: ParserTypeVariant::Array(parser_type_id)
                 });
                 backup_pos = self.source.pos();
                 // In case we're dealing with another array
                 self.consume_whitespace(false)?;
             } else {
                 return Err(ParseError2::new_error(
                     &self.source, pos,
                     "Expected a closing ']'"
                 ));
+            }
+        }
         self.source.seek(backup_pos);
         Ok(parser_type_id)
+    }
     /// Attempts to consume a type without returning it. If it doesn't encounter
     /// a well-formed type, then the input position is left at a "random"
     /// position.
     fn maybe_consume_type_spilled_without_pos_recovery(&mut self) -> bool {
         // Consume type identifier
         if self.has_type_keyword() {
             self.consume_any_chars();
         } else {
             let ident = self.consume_namespaced_identifier();
             if ident.is_err() { return false; }
+        }
         // Consume any polymorphic arguments that follow the type identifier
         let mut backup_pos = self.source.pos();
         if self.consume_whitespace(false).is_err() { return false; }
         if !self.maybe_consume_poly_args_spilled_without_pos_recovery() { return false; }
         // Consume any array specifiers. Make sure we always leave the input
         // position at the end of the last array specifier if we do find a
         // valid type
         if self.consume_whitespace(false).is_err() { return false; }
         while let Some(b'[') = self.source.next() {
             self.source.consume();
             if self.consume_whitespace(false).is_err() { return false; }
             if self.source.next() != Some(b']') { return false; }
             self.source.consume();
             backup_pos = self.source.pos();
             if self.consume_whitespace(false).is_err() { return false; }
+        }
         self.source.seek(backup_pos);
         return true;
+    }
     fn maybe_consume_type_spilled(&mut self) -> bool {
         let backup_pos = self.source.pos();
         if !self.maybe_consume_type_spilled_without_pos_recovery() {
             self.source.seek(backup_pos);
             return false;
+        }
         return true;
+    }
     /// Attempts to consume polymorphic arguments without returning them. If it
     /// doesn't encounter well-formed polymorphic arguments, then the input
     /// position is left at a "random" position.
     fn maybe_consume_poly_args_spilled_without_pos_recovery(&mut self) -> bool {
         self.consume_comma_separated_spilled_without_pos_recovery(
             b'<', b'>', |lexer| {
                 lexer.maybe_consume_type_spilled_without_pos_recovery()
             })
+    }
     /// Consumes polymorphic arguments and its delimiters if specified. If
     /// polyargs are present then the args are consumed and the input position
     /// will be placed after the polyarg list. If polyargs are not present then
     /// the input position will remain unmodified and an empty vector will be
     /// returned.
     ///
     /// Polymorphic arguments represent the specification of the parametric
     /// types of a polymorphic type: they specify the value of the polymorphic
     /// type's polymorphic variables.
     fn consume_polymorphic_args(&mut self, h: &mut Heap, allow_inference: bool) -> Result<Vec<ParserTypeId>, ParseError2> {
         let backup_pos = self.source.pos();
         match self.consume_comma_separated(
             h, b'<', b'>', "Expected the end of the polymorphic argument list",
             |lexer, heap| lexer.consume_type2(heap, allow_inference)
         )? {
             Some(poly_args) => Ok(poly_args),
             None => {
                 self.source.seek(backup_pos);
                 Ok(vec![])
+            }
+        }
+    }
     /// Consumes polymorphic variables. These are identifiers that are used
     /// within polymorphic types. The input position may be at whitespace. If
     /// polymorphic variables are present then the whitespace, wrapping
     /// delimiters and the polymorphic variables are consumed. Otherwise the
     /// input position will stay where it is. If no polymorphic variables are
     /// present then an empty vector will be returned.
     fn consume_polymorphic_vars(&mut self, h: &mut Heap) -> Result<Vec<Identifier>, ParseError2> {
         let backup_pos = self.source.pos();
         match self.consume_comma_separated(
             h, b'<', b'>', "Expected the end of the polymorphic variable list",
             |lexer, _heap| lexer.consume_identifier()
         )? {
             Some(poly_vars) => Ok(poly_vars),
             None => {
                 self.source.seek(backup_pos);
                 Ok(vec!())
+            }
+        }
+    }
     // Parameters
     fn consume_parameter(&mut self, h: &mut Heap) -> Result<ParameterId, ParseError2> {
         let parser_type = self.consume_type2(h, false)?;
         self.consume_whitespace(true)?;
         let position = self.source.pos();
         let identifier = self.consume_identifier()?;
         let id =
             h.alloc_parameter(|this| Parameter { this, position, parser_type, identifier });
         Ok(id)
+    }
     fn consume_parameters(&mut self, h: &mut Heap) -> Result<Vec<ParameterId>, ParseError2> {
         match self.consume_comma_separated(
             h, b'(', b')', "Expected the end of the parameter list",
             |lexer, heap| lexer.consume_parameter(heap)
         )? {
             Some(params) => Ok(params),
             None => {
                 Err(ParseError2::new_error(
                     &self.source, self.source.pos(),
                     "Expected a parameter list"
                 ))
+            }
+        }
+    }
     // ====================
     // Expressions
     // ====================
     fn consume_paren_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         self.consume_string(b"(")?;
         self.consume_whitespace(false)?;
         let result = self.consume_expression(h)?;
         self.consume_whitespace(false)?;
         self.consume_string(b")")?;
         Ok(result)
+    }
     fn consume_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         if self.level >= MAX_LEVEL {
             return Err(self.error_at_pos("Too deeply nested expression"));
+        }
         self.level += 1;
         let result = self.consume_assignment_expression(h);
         self.level -= 1;
         result
+    }
     fn consume_assignment_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         let result = self.consume_conditional_expression(h)?;
         self.consume_whitespace(false)?;
         if self.has_assignment_operator() {
             let position = self.source.pos();
             let left = result;
             let operation = self.consume_assignment_operator()?;
             self.consume_whitespace(false)?;
             let right = self.consume_expression(h)?;
             Ok(h.alloc_assignment_expression(|this| AssignmentExpression {
                 this,
                 position,
                 left,
                 operation,
                 right,
                 parent: ExpressionParent::None,
                 concrete_type: ConcreteType::default(),
             })
             .upcast())
         } else {
             Ok(result)
+        }
+    }
     fn has_assignment_operator(&self) -> bool {
         self.has_string(b"=")
             || self.has_string(b"*=")
             || self.has_string(b"/=")
             || self.has_string(b"%=")
             || self.has_string(b"+=")
             || self.has_string(b"-=")
             || self.has_string(b"<<=")
             || self.has_string(b">>=")
             || self.has_string(b"&=")
             || self.has_string(b"^=")
             || self.has_string(b"|=")
+    }
     fn consume_assignment_operator(&mut self) -> Result<AssignmentOperator, ParseError2> {
         if self.has_string(b"=") {
             self.consume_string(b"=")?;
             Ok(AssignmentOperator::Set)
         } else if self.has_string(b"*=") {
             self.consume_string(b"*=")?;
             Ok(AssignmentOperator::Multiplied)
         } else if self.has_string(b"/=") {
             self.consume_string(b"/=")?;
             Ok(AssignmentOperator::Divided)
         } else if self.has_string(b"%=") {
             self.consume_string(b"%=")?;
             Ok(AssignmentOperator::Remained)
         } else if self.has_string(b"+=") {
             self.consume_string(b"+=")?;
             Ok(AssignmentOperator::Added)
         } else if self.has_string(b"-=") {
             self.consume_string(b"-=")?;
             Ok(AssignmentOperator::Subtracted)
         } else if self.has_string(b"<<=") {
             self.consume_string(b"<<=")?;
             Ok(AssignmentOperator::ShiftedLeft)
         } else if self.has_string(b">>=") {
             self.consume_string(b">>=")?;
             Ok(AssignmentOperator::ShiftedRight)
         } else if self.has_string(b"&=") {
             self.consume_string(b"&=")?;
             Ok(AssignmentOperator::BitwiseAnded)
         } else if self.has_string(b"^=") {
             self.consume_string(b"^=")?;
             Ok(AssignmentOperator::BitwiseXored)
         } else if self.has_string(b"|=") {
             self.consume_string(b"|=")?;
             Ok(AssignmentOperator::BitwiseOred)
         } else {
             Err(self.error_at_pos("Expected assignment operator"))
+        }
+    }
     fn consume_conditional_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         let result = self.consume_concat_expression(h)?;
         self.consume_whitespace(false)?;
         if self.has_string(b"?") {
             let position = self.source.pos();
             let test = result;
             self.consume_string(b"?")?;
             self.consume_whitespace(false)?;
             let true_expression = self.consume_expression(h)?;
             self.consume_whitespace(false)?;
             self.consume_string(b":")?;
             self.consume_whitespace(false)?;
             let false_expression = self.consume_expression(h)?;
             Ok(h.alloc_conditional_expression(|this| ConditionalExpression {
                 this,
                 position,
                 test,
                 true_expression,
                 false_expression,
                 parent: ExpressionParent::None,
                 concrete_type: ConcreteType::default(),
             })
             .upcast())
         } else {
             Ok(result)
+        }
+    }
     fn consume_concat_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         let mut result = self.consume_lor_expression(h)?;
         self.consume_whitespace(false)?;
         while self.has_string(b"@") {
             let position = self.source.pos();
             let left = result;
             self.consume_string(b"@")?;
             let operation = BinaryOperator::Concatenate;
             self.consume_whitespace(false)?;
             let right = self.consume_lor_expression(h)?;
             self.consume_whitespace(false)?;
             result = h
                 .alloc_binary_expression(|this| BinaryExpression {
                     this,
                     position,
                     left,
                     operation,
                     right,
                     parent: ExpressionParent::None,
                     concrete_type: ConcreteType::default(),
                 })
                 .upcast();
+        }
         Ok(result)
+    }
     fn consume_lor_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         let mut result = self.consume_land_expression(h)?;
         self.consume_whitespace(false)?;
         while self.has_string(b"||") {
             let position = self.source.pos();
             let left = result;
             self.consume_string(b"||")?;
             let operation = BinaryOperator::LogicalOr;
             self.consume_whitespace(false)?;
             let right = self.consume_land_expression(h)?;
             self.consume_whitespace(false)?;
             result = h
                 .alloc_binary_expression(|this| BinaryExpression {
                     this,
                     position,
                     left,
                     operation,
                     right,
                     parent: ExpressionParent::None,
                     concrete_type: ConcreteType::default(),
                 })
                 .upcast();
+        }
         Ok(result)
+    }
     fn consume_land_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         let mut result = self.consume_bor_expression(h)?;
         self.consume_whitespace(false)?;
         while self.has_string(b"&&") {
             let position = self.source.pos();
             let left = result;
             self.consume_string(b"&&")?;
             let operation = BinaryOperator::LogicalAnd;
             self.consume_whitespace(false)?;
             let right = self.consume_bor_expression(h)?;
             self.consume_whitespace(false)?;
             result = h
                 .alloc_binary_expression(|this| BinaryExpression {
                     this,
                     position,
                     left,
                     operation,
                     right,
                     parent: ExpressionParent::None,
                     concrete_type: ConcreteType::default(),
                 })
                 .upcast();
+        }
         Ok(result)
+    }
     fn consume_bor_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         let mut result = self.consume_xor_expression(h)?;
         self.consume_whitespace(false)?;
         while self.has_string(b"|") && !self.has_string(b"||") && !self.has_string(b"|=") {
             let position = self.source.pos();
             let left = result;
             self.consume_string(b"|")?;
             let operation = BinaryOperator::BitwiseOr;
             self.consume_whitespace(false)?;
             let right = self.consume_xor_expression(h)?;
             self.consume_whitespace(false)?;
             result = h
                 .alloc_binary_expression(|this| BinaryExpression {
                     this,
                     position,
                     left,
                     operation,
                     right,
                     parent: ExpressionParent::None,
                     concrete_type: ConcreteType::default(),
                 })
                 .upcast();
+        }
         Ok(result)
+    }
     fn consume_xor_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         let mut result = self.consume_band_expression(h)?;
         self.consume_whitespace(false)?;
         while self.has_string(b"^") && !self.has_string(b"^=") {
             let position = self.source.pos();
             let left = result;
             self.consume_string(b"^")?;
             let operation = BinaryOperator::BitwiseXor;
             self.consume_whitespace(false)?;
             let right = self.consume_band_expression(h)?;
             self.consume_whitespace(false)?;
             result = h
                 .alloc_binary_expression(|this| BinaryExpression {
                     this,
                     position,
                     left,
                     operation,
                     right,
                     parent: ExpressionParent::None,
                     concrete_type: ConcreteType::default(),
                 })
                 .upcast();
+        }
         Ok(result)
+    }
     fn consume_band_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         let mut result = self.consume_eq_expression(h)?;
         self.consume_whitespace(false)?;
         while self.has_string(b"&") && !self.has_string(b"&&") && !self.has_string(b"&=") {
             let position = self.source.pos();
             let left = result;
             self.consume_string(b"&")?;
             let operation = BinaryOperator::BitwiseAnd;
             self.consume_whitespace(false)?;
             let right = self.consume_eq_expression(h)?;
             self.consume_whitespace(false)?;
             result = h
                 .alloc_binary_expression(|this| BinaryExpression {
                     this,
                     position,
                     left,
                     operation,
                     right,
                     parent: ExpressionParent::None,
                     concrete_type: ConcreteType::default(),
                 })
                 .upcast();
+        }
         Ok(result)
+    }
     fn consume_eq_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         let mut result = self.consume_rel_expression(h)?;
         self.consume_whitespace(false)?;
         while self.has_string(b"==") || self.has_string(b"!=") {
             let position = self.source.pos();
             let left = result;
             let operation;
             if self.has_string(b"==") {
                 self.consume_string(b"==")?;
                 operation = BinaryOperator::Equality;
             } else {
                 self.consume_string(b"!=")?;
                 operation = BinaryOperator::Inequality;
+            }
             self.consume_whitespace(false)?;
             let right = self.consume_rel_expression(h)?;
             self.consume_whitespace(false)?;
             result = h
                 .alloc_binary_expression(|this| BinaryExpression {
                     this,
                     position,
                     left,
                     operation,
                     right,
                     parent: ExpressionParent::None,
                     concrete_type: ConcreteType::default(),
                 })
                 .upcast();
+        }
         Ok(result)
+    }
     fn consume_rel_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         let mut result = self.consume_shift_expression(h)?;
         self.consume_whitespace(false)?;
         while self.has_string(b"<=")
             || self.has_string(b">=")
             || self.has_string(b"<") && !self.has_string(b"<<=")
             || self.has_string(b">") && !self.has_string(b">>=")
+        {
             let position = self.source.pos();
             let left = result;
             let operation;
             if self.has_string(b"<=") {
                 self.consume_string(b"<=")?;
                 operation = BinaryOperator::LessThanEqual;
             } else if self.has_string(b">=") {
                 self.consume_string(b">=")?;
                 operation = BinaryOperator::GreaterThanEqual;
             } else if self.has_string(b"<") {
                 self.consume_string(b"<")?;
                 operation = BinaryOperator::LessThan;
             } else {
                 self.consume_string(b">")?;
                 operation = BinaryOperator::GreaterThan;
+            }
             self.consume_whitespace(false)?;
             let right = self.consume_shift_expression(h)?;
             self.consume_whitespace(false)?;
             result = h
                 .alloc_binary_expression(|this| BinaryExpression {
                     this,
                     position,
                     left,
                     operation,
                     right,
                     parent: ExpressionParent::None,
                     concrete_type: ConcreteType::default(),
                 })
                 .upcast();
+        }
         Ok(result)
+    }
     fn consume_shift_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         let mut result = self.consume_add_expression(h)?;
         self.consume_whitespace(false)?;
         while self.has_string(b"<<") && !self.has_string(b"<<=")
             || self.has_string(b">>") && !self.has_string(b">>=")
+        {
             let position = self.source.pos();
             let left = result;
             let operation;
             if self.has_string(b"<<") {
                 self.consume_string(b"<<")?;
                 operation = BinaryOperator::ShiftLeft;
             } else {
                 self.consume_string(b">>")?;
                 operation = BinaryOperator::ShiftRight;
+            }
             self.consume_whitespace(false)?;
             let right = self.consume_add_expression(h)?;
             self.consume_whitespace(false)?;
             result = h
                 .alloc_binary_expression(|this| BinaryExpression {
                     this,
                     position,
                     left,
                     operation,
                     right,
                     parent: ExpressionParent::None,
                     concrete_type: ConcreteType::default(),
                 })
                 .upcast();
+        }
         Ok(result)
+    }
     fn consume_add_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         let mut result = self.consume_mul_expression(h)?;
         self.consume_whitespace(false)?;
         while self.has_string(b"+") && !self.has_string(b"+=")
             || self.has_string(b"-") && !self.has_string(b"-=")
+        {
             let position = self.source.pos();
             let left = result;
             let operation;
             if self.has_string(b"+") {
                 self.consume_string(b"+")?;
                 operation = BinaryOperator::Add;
             } else {
                 self.consume_string(b"-")?;
                 operation = BinaryOperator::Subtract;
+            }
             self.consume_whitespace(false)?;
             let right = self.consume_mul_expression(h)?;
             self.consume_whitespace(false)?;
             result = h
                 .alloc_binary_expression(|this| BinaryExpression {
                     this,
                     position,
                     left,
                     operation,
                     right,
                     parent: ExpressionParent::None,
                     concrete_type: ConcreteType::default(),
                 })
                 .upcast();
+        }
         Ok(result)
+    }
     fn consume_mul_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         let mut result = self.consume_prefix_expression(h)?;
         self.consume_whitespace(false)?;
         while self.has_string(b"*") && !self.has_string(b"*=")
             || self.has_string(b"/") && !self.has_string(b"/=")
             || self.has_string(b"%") && !self.has_string(b"%=")
+        {
             let position = self.source.pos();
             let left = result;
             let operation;
             if self.has_string(b"*") {
                 self.consume_string(b"*")?;
                 operation = BinaryOperator::Multiply;
             } else if self.has_string(b"/") {
                 self.consume_string(b"/")?;
                 operation = BinaryOperator::Divide;
             } else {
                 self.consume_string(b"%")?;
                 operation = BinaryOperator::Remainder;
+            }
             self.consume_whitespace(false)?;
             let right = self.consume_prefix_expression(h)?;
             self.consume_whitespace(false)?;
             result = h
                 .alloc_binary_expression(|this| BinaryExpression {
                     this,
                     position,
                     left,
                     operation,
                     right,
                     parent: ExpressionParent::None,
                     concrete_type: ConcreteType::default(),
                 })
                 .upcast();
+        }
         Ok(result)
+    }
     fn consume_prefix_expression(&mut self, h: &mut Heap) -> Result<ExpressionId, ParseError2> {
         if self.has_string(b"+")
             || self.has_string(b"-")
             || self.has_string(b"~")
             || self.has_string(b"!")
+        {
             let position = self.source.pos();
             let operation;
             if self.has_string(b"+") {
                 self.consume_string(b"+")?;
                 if self.has_string(b"+") {
                     self.consume_string(b"+")?;
                     operation = UnaryOperation::PreIncrement;
                 } else {
                     operation = UnaryOperation::Positive;
+                }
             } else if self.has_string(b"-") {
                 self.consume_string(b"-")?;
                 if self.has_string(b"-") {
                     self.consume_string(b"-")?;
                     operation = UnaryOperation::PreDecrement;
                 } else {
                     operation = UnaryOperation::Negative;

src/protocol/parser/type_resolver.rs

➞

Show inline comments

 /// type_resolver.rs
 ///
 /// Performs type inference and type checking. Type inference is implemented by
 /// applying constraints on (sub)trees of types. During this process the
 /// resolver takes the `ParserType` structs (the representation of the types
 /// written by the programmer), converts them to `InferenceType` structs (the
 /// temporary data structure used during type inference) and attempts to arrive
 /// at `ConcreteType` structs (the representation of a fully checked and
 /// validated type).
 ///
 /// The resolver will visit every statement and expression relevant to the
 /// procedure and insert and determine its initial type based on context (e.g. a
 /// return statement's expression must match the function's return type, an
 /// if statement's test expression must evaluate to a boolean). When all are
 /// visited we attempt to make progress in evaluating the types. Whenever a type
 /// is progressed we queue the related expressions for further type progression.
 /// Once no more expressions are in the queue the algorithm is finished. At this
 /// point either all types are inferred (or can be trivially implicitly
 /// determined), or we have incomplete types. In the latter casee we return an
 /// error.
 ///
 /// Inference may be applied on non-polymorphic procedures and on polymorphic
 /// procedures. When dealing with a non-polymorphic procedure we apply the type
 /// resolver and annotate the AST with the `ConcreteType`s. When dealing with
 /// polymorphic procedures we will only annotate the AST once, preserving
 /// references to polymorphic variables. Any later pass will perform just the
 /// type checking.
 ///
 /// TODO: Needs an optimization pass
 /// TODO: Needs a cleanup pass
 ///     slightly more specific: initially it seemed that expressions just need
 ///     to apply constraints between their expression types and the expression
 ///     types of the arguments. But it seems to appear more-and-more that the
 ///     expressions may need their own little datastructures. Using some kind of
 ///     scratch allocator and proper considerations for dependencies might lead
 ///     to a much more efficient algorithm
 /// TODO: Disallow `Void` types in various expressions (and other future types)
 /// TODO: Maybe remove msg type?
 macro_rules! enabled_debug_print {
     (false, $name:literal, $format:literal) => {};
     (false, $name:literal, $format:literal, $($args:expr),*) => {};
     (true, $name:literal, $format:literal) => {
         println!("[{}] {}", $name, $format)
     };
     (true, $name:literal, $format:literal, $($args:expr),*) => {
         println!("[{}] {}", $name, format!($format, $($args),*))
     };
+}
 macro_rules! debug_log {
     ($format:literal) => {
         enabled_debug_print!(true, "types", $format);
     };
     ($format:literal, $($args:expr),*) => {
         enabled_debug_print!(true, "types", $format, $($args),*);
     };
+}
 use std::collections::{HashMap, HashSet, VecDeque};
 use crate::protocol::ast::*;
 use crate::protocol::inputsource::*;
 use super::type_table::*;
 use super::symbol_table::*;
 use crate::protocol::parser::type_table::*;
 use super::visitor::{
     STMT_BUFFER_INIT_CAPACITY,
     EXPR_BUFFER_INIT_CAPACITY,
     Ctx,
     Visitor2,
     VisitorResult
 };
 use std::collections::hash_map::Entry;
 use crate::protocol::parser::type_resolver::InferenceTypePart::IntegerLike;
 const MESSAGE_TEMPLATE: [InferenceTypePart; 2] = [ InferenceTypePart::Message, InferenceTypePart::Byte ];
 const BOOL_TEMPLATE: [InferenceTypePart; 1] = [ InferenceTypePart::Bool ];
 const NUMBERLIKE_TEMPLATE: [InferenceTypePart; 1] = [ InferenceTypePart::NumberLike ];
 const INTEGERLIKE_TEMPLATE: [InferenceTypePart; 1] = [ InferenceTypePart::IntegerLike ];
 const ARRAY_TEMPLATE: [InferenceTypePart; 2] = [ InferenceTypePart::Array, InferenceTypePart::Unknown ];
 const ARRAYLIKE_TEMPLATE: [InferenceTypePart; 2] = [ InferenceTypePart::ArrayLike, InferenceTypePart::Unknown ];
 const PORTLIKE_TEMPLATE: [InferenceTypePart; 2] = [ InferenceTypePart::PortLike, InferenceTypePart::Unknown ];
 /// TODO: @performance Turn into PartialOrd+Ord to simplify checks
 /// TODO: @types Remove the Message -> Byte hack at some point...
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub(crate) enum InferenceTypePart {
     // A marker with an identifier which we can use to retrieve the type subtree
     // that follows the marker. This is used to perform type inference on
     // polymorphs: an expression may determine the polymorphs type, after we
     // need to apply that information to all other places where the polymorph is
     // used.
     // TODO: @rename to something appropriate, I keep confusing myself...
     MarkerDefinition(usize), // marker for polymorph types on a procedure's definition
     MarkerBody(usize), // marker for polymorph types within a procedure body
     // Completely unknown type, needs to be inferred
     Unknown,
     // Partially known type, may be inferred to to be the appropriate related
     // type.
     // IndexLike,      // index into array/slice
     NumberLike,     // any kind of integer/float
     IntegerLike,    // any kind of integer
     ArrayLike,      // array or slice. Note that this must have a subtype
     PortLike,       // input or output port
     // Special types that cannot be instantiated by the user
     Void, // For builtin functions that do not return anything
     // Concrete types without subtypes
     Bool,
     Byte,
     Short,
     Int,
     Long,
     String,
     // One subtype
     Message,
     Array,
     Slice,
     Input,
     Output,
     // A user-defined type with any number of subtypes
     Instance(DefinitionId, usize)
+}
 impl InferenceTypePart {
     fn is_marker(&self) -> bool {
         use InferenceTypePart as ITP;
         match self {
             ITP::MarkerDefinition(_) | ITP::MarkerBody(_) => true,
             _ => false,
+        }
+    }
     /// Checks if the type is concrete, markers are interpreted as concrete
     /// types.
     fn is_concrete(&self) -> bool {
         use InferenceTypePart as ITP;
         match self {
             ITP::Unknown | ITP::NumberLike | ITP::IntegerLike |
             ITP::ArrayLike | ITP::PortLike => false,
             _ => true
+        }
+    }
     fn is_concrete_number(&self) -> bool {
         // TODO: @float
         use InferenceTypePart as ITP;
         match self {
             ITP::Byte | ITP::Short | ITP::Int | ITP::Long => true,
             _ => false,
+        }
+    }
     fn is_concrete_integer(&self) -> bool {
         use InferenceTypePart as ITP;
         match self {
             ITP::Byte | ITP::Short | ITP::Int | ITP::Long => true,
             _ => false,
+        }
+    }
     fn is_concrete_msg_array_or_slice(&self) -> bool {
         use InferenceTypePart as ITP;
         match self {
             ITP::Array | ITP::Slice | ITP::Message => true,
             _ => false,
+        }
+    }
     fn is_concrete_port(&self) -> bool {
         use InferenceTypePart as ITP;
         match self {
             ITP::Input | ITP::Output => true,
             _ => false,
+        }
+    }
     /// Checks if a part is less specific than the argument. Only checks for
     /// single-part inference (i.e. not the replacement of an `Unknown` variant
     /// with the argument)
     fn may_be_inferred_from(&self, arg: &InferenceTypePart) -> bool {
         use InferenceTypePart as ITP;
         (*self == ITP::IntegerLike && arg.is_concrete_integer()) ||
         (*self == ITP::NumberLike && (arg.is_concrete_number() || *arg == ITP::IntegerLike)) ||
         (*self == ITP::ArrayLike && arg.is_concrete_msg_array_or_slice()) ||
         (*self == ITP::PortLike && arg.is_concrete_port())
+    }
     /// Returns the change in "iteration depth" when traversing this particular
     /// part. The iteration depth is used to traverse the tree in a linear
     /// fashion. It is basically `number_of_subtypes - 1`
     fn depth_change(&self) -> i32 {
         use InferenceTypePart as ITP;
         match &self {
             ITP::Unknown | ITP::NumberLike | ITP::IntegerLike |
             ITP::Void | ITP::Bool |
             ITP::Byte | ITP::Short | ITP::Int | ITP::Long |
             ITP::String => {
                 -1
             },
             ITP::MarkerDefinition(_) | ITP::MarkerBody(_) |
             ITP::ArrayLike | ITP::Message | ITP::Array | ITP::Slice |
             ITP::PortLike | ITP::Input | ITP::Output => {
                 // One subtype, so do not modify depth
             },
             ITP::Instance(_, num_args) => {
                 (*num_args as i32) - 1
+            }
+        }
+    }
+}
 impl From<ConcreteTypePart> for InferenceTypePart {
     fn from(v: ConcreteTypePart) -> InferenceTypePart {
         use ConcreteTypePart as CTP;
         use InferenceTypePart as ITP;
         match v {
             CTP::Marker(_) => {
                 unreachable!("encountered marker while converting concrete type to inferred type");
+            }
             CTP::Void => ITP::Void,
             CTP::Message => ITP::Message,
             CTP::Bool => ITP::Bool,
             CTP::Byte => ITP::Byte,
             CTP::Short => ITP::Short,
             CTP::Int => ITP::Int,
             CTP::Long => ITP::Long,
             CTP::String => ITP::String,
             CTP::Array => ITP::Array,
             CTP::Slice => ITP::Slice,
             CTP::Input => ITP::Input,
             CTP::Output => ITP::Output,
             CTP::Instance(id, num) => ITP::Instance(id, num),
+        }
+    }
+}
 #[derive(Debug)]
 struct InferenceType {
     has_body_marker: bool,
     is_done: bool,
     parts: Vec<InferenceTypePart>,
+}
 impl InferenceType {
     /// Generates a new InferenceType. The two boolean flags will be checked in
     /// debug mode.
     fn new(has_body_marker: bool, is_done: bool, parts: Vec<InferenceTypePart>) -> Self {
         if cfg!(debug_assertions) {
             debug_assert!(!parts.is_empty());
             if !has_body_marker {
                 debug_assert!(parts.iter().all(|v| {
                     if let InferenceTypePart::MarkerBody(_) = v { false } else { true }
                 }));
+            }
             if is_done {
                 debug_assert!(parts.iter().all(|v| v.is_concrete()));
+            }
+        }
         Self{ has_body_marker: has_body_marker, is_done, parts }
+    }
     /// Replaces a type subtree with the provided subtree. The caller must make
     /// sure the the replacement is a well formed type subtree.
     fn replace_subtree(&mut self, start_idx: usize, with: &[InferenceTypePart]) {
         let end_idx = Self::find_subtree_end_idx(&self.parts, start_idx);
         debug_assert_eq!(with.len(), Self::find_subtree_end_idx(with, 0));
         self.parts.splice(start_idx..end_idx, with.iter().cloned());
         self.recompute_is_done();
+    }
     // TODO: @performance, might all be done inline in the type inference methods
     fn recompute_is_done(&mut self) {
         self.is_done = self.parts.iter().all(|v| v.is_concrete());
+    }
     /// Returns an iterator over all body markers and the partial type tree that
     /// follows those markers.
     fn body_marker_iter(&self) -> InferenceTypeMarkerIter {
         InferenceTypeMarkerIter::new(&self.parts)
+    }
     /// Attempts to find a specific type part appearing at or after the
     /// specified index. If found then the partial type tree's bounding indices
     /// that follow that marker are returned.
     fn find_subtree_idx_for_part(&self, part: InferenceTypePart, mut idx: usize) -> Option<(usize, usize)> {
         debug_assert!(part.depth_change() >= 0, "cannot find subtree for leaf part");
         while idx < self.parts.len() {
             if part == self.parts[idx] {
                 // Found the specified part
                 let start_idx = idx + 1;
                 let end_idx = Self::find_subtree_end_idx(&self.parts, start_idx);
                 return Some((start_idx, end_idx))
+            }
             idx += 1;
+        }
         None
+    }
     /// Given that the `parts` are a depth-first serialized tree of types, this
     /// function finds the subtree anchored at a specific node. The returned
     /// index is exclusive.
     fn find_subtree_end_idx(parts: &[InferenceTypePart], start_idx: usize) -> usize {
         let mut depth = 1;
         let mut idx = start_idx;
         while idx < parts.len() {
             depth += parts[idx].depth_change();
             if depth == 0 {
                 return idx + 1;
+            }
             idx += 1;
+        }
         // If here, then the inference type is malformed
         unreachable!();
+    }
     /// Call that attempts to infer the part at `to_infer.parts[to_infer_idx]`
     /// using the subtree at `template.parts[template_idx]`. Will return
     /// `Some(depth_change_due_to_traversal)` if type inference has been
     /// applied. In this case the indices will also be modified to point to the
     /// next part in both templates. If type inference has not (or: could not)
     /// be applied then `None` will be returned. Note that this might mean that
     /// the types are incompatible.
     ///
     /// As this is a helper functions, some assumptions: the parts are not
     /// exactly equal, and neither of them contains a marker. Also: only the
     /// `to_infer` parts are checked for inference. It might be that this
     /// function returns `None`, but that that `template` is still compatible
     /// with `to_infer`, e.g. when `template` has an `Unknown` part.
     fn infer_part_for_single_type(
         to_infer: &mut InferenceType, to_infer_idx: &mut usize,
         template_parts: &[InferenceTypePart], template_idx: &mut usize,
     ) -> Option<i32> {
         use InferenceTypePart as ITP;
         let to_infer_part = &to_infer.parts[*to_infer_idx];
         let template_part = &template_parts[*template_idx];
         // TODO: Maybe do this differently?
         let mut template_definition_marker = None;
         if *template_idx > 0 {
             if let ITP::MarkerDefinition(marker) = &template_parts[*template_idx - 1] {
                 template_definition_marker = Some(*marker)
+            }
+        }
         // Check for programmer mistakes
         debug_assert_ne!(to_infer_part, template_part);
         debug_assert!(!to_infer_part.is_marker(), "marker encountered in 'infer part'");
         debug_assert!(!template_part.is_marker(), "marker encountered in 'template part'");
         // Inference of a somewhat-specified type
         if to_infer_part.may_be_inferred_from(template_part) {
             let depth_change = to_infer_part.depth_change();
             debug_assert_eq!(depth_change, template_part.depth_change());
             if let Some(marker) = template_definition_marker {
                 to_infer.parts.insert(*to_infer_idx, ITP::MarkerDefinition(marker));
                 *to_infer_idx += 1;
+            }
             to_infer.parts[*to_infer_idx] = template_part.clone();
             *to_infer_idx += 1;
             *template_idx += 1;
             return Some(depth_change);
+        }
         // Inference of a completely unknown type
         if *to_infer_part == ITP::Unknown {
             // template part is different, so cannot be unknown, hence copy the
             // entire subtree
             let template_end_idx = Self::find_subtree_end_idx(template_parts, *template_idx);
             let erase_offset = if let Some(marker) = template_definition_marker {
                 to_infer.parts[*to_infer_idx] = ITP::MarkerDefinition(marker);
                 *to_infer_idx += 1;
             } else {
             };
             to_infer.parts.splice(
                 *to_infer_idx..*to_infer_idx + erase_offset,
                 template_parts[*template_idx..template_end_idx].iter().cloned()
             );
-            *to_infer_idx += (template_end_idx - *template_idx);
             *to_infer_idx += template_end_idx - *template_idx;
             *template_idx = template_end_idx;
             // Note: by definition the LHS was Unknown and the RHS traversed a
             // full subtree.
             return Some(-1);
+        }
         None
+    }
     /// Call that checks if the `to_check` part is compatible with the `infer`
     /// part. This is essentially a copy of `infer_part_for_single_type`, but
     /// without actually copying the type parts.
     fn check_part_for_single_type(
         to_check_parts: &[InferenceTypePart], to_check_idx: &mut usize,
         template_parts: &[InferenceTypePart], template_idx: &mut usize
     ) -> Option<i32> {
         use InferenceTypePart as ITP;
         let to_check_part = &to_check_parts[*to_check_idx];
         let template_part = &template_parts[*template_idx];
         // Checking programmer errors
         debug_assert_ne!(to_check_part, template_part);
         debug_assert!(!to_check_part.is_marker(), "marker encountered in 'to_check part'");
         debug_assert!(!template_part.is_marker(), "marker encountered in 'template part'");
         if to_check_part.may_be_inferred_from(template_part) {
             let depth_change = to_check_part.depth_change();
             debug_assert_eq!(depth_change, template_part.depth_change());
             *to_check_idx += 1;
             *template_idx += 1;
             return Some(depth_change);
+        }
         if *to_check_part == ITP::Unknown {
             *to_check_idx += 1;
             *template_idx = Self::find_subtree_end_idx(template_parts, *template_idx);
             // By definition LHS and RHS had depth change of -1
             return Some(-1);
+        }
         None
+    }
     /// Attempts to infer types between two `InferenceType` instances. This
     /// function is unsafe as it accepts pointers to work around Rust's
     /// borrowing rules. The caller must ensure that the pointers are distinct.
     unsafe fn infer_subtrees_for_both_types(
         type_a: *mut InferenceType, start_idx_a: usize,
         type_b: *mut InferenceType, start_idx_b: usize
     ) -> DualInferenceResult {
         use InferenceTypePart as ITP;
         debug_assert!(!std::ptr::eq(type_a, type_b), "encountered pointers to the same inference type");
         let type_a = &mut *type_a;
         let type_b = &mut *type_b;
         let mut modified_a = false;
         let mut modified_b = false;
         let mut idx_a = start_idx_a;
         let mut idx_b = start_idx_b;
         let mut depth = 1;
         while depth > 0 {
             // Advance indices if we encounter markers or equal parts
             let part_a = &type_a.parts[idx_a];
             let part_b = &type_b.parts[idx_b];
             if part_a == part_b {
                 let depth_change = part_a.depth_change();
                 depth += depth_change;
                 debug_assert_eq!(depth_change, part_b.depth_change());
                 idx_a += 1;
                 idx_b += 1;
                 continue;
+            }
             if part_a.is_marker() { idx_a += 1; continue; }
             if part_b.is_marker() { idx_b += 1; continue; }
             // Types are not equal and are both not markers
             if let Some(depth_change) = Self::infer_part_for_single_type(type_a, &mut idx_a, &type_b.parts, &mut idx_b) {
                 depth += depth_change;
                 modified_a = true;
                 continue;
+            }
             if let Some(depth_change) = Self::infer_part_for_single_type(type_b, &mut idx_b, &type_a.parts, &mut idx_a) {
                 depth += depth_change;
                 modified_b = true;
                 continue;
+            }
             // And can also not be inferred in any way: types must be incompatible
             return DualInferenceResult::Incompatible;
+        }
         if modified_a { type_a.recompute_is_done(); }
         if modified_b { type_b.recompute_is_done(); }
         // If here then we completely inferred the subtrees.
         match (modified_a, modified_b) {
             (false, false) => DualInferenceResult::Neither,
             (false, true) => DualInferenceResult::Second,
             (true, false) => DualInferenceResult::First,
             (true, true) => DualInferenceResult::Both
+        }
+    }
     /// Attempts to infer the first subtree based on the template. Like
     /// `infer_subtrees_for_both_types`, but now only applying inference to
     /// `to_infer` based on the type information in `template`.
     /// Secondary use is to make sure that a type follows a certain template.
     fn infer_subtree_for_single_type(
         to_infer: &mut InferenceType, mut to_infer_idx: usize,
         template: &[InferenceTypePart], mut template_idx: usize,
     ) -> SingleInferenceResult {
         let mut modified = false;
         let mut depth = 1;
         while depth > 0 {
             let to_infer_part = &to_infer.parts[to_infer_idx];
             let template_part = &template[template_idx];
             if to_infer_part == template_part {
                 let depth_change = to_infer_part.depth_change();
                 depth += depth_change;
                 debug_assert_eq!(depth_change, template_part.depth_change());
                 to_infer_idx += 1;
                 template_idx += 1;
                 continue;
+            }
             if to_infer_part.is_marker() { to_infer_idx += 1; continue; }
             if template_part.is_marker() { template_idx += 1; continue; }
             // Types are not equal and not markers. So check if we can infer
             // anything
             if let Some(depth_change) = Self::infer_part_for_single_type(
                 to_infer, &mut to_infer_idx, template, &mut template_idx
             ) {
                 depth += depth_change;
                 modified = true;
                 continue;
+            }
             // We cannot infer anything, but the template may still be
             // compatible with the type we're inferring
             if let Some(depth_change) = Self::check_part_for_single_type(
                 template, &mut template_idx, &to_infer.parts, &mut to_infer_idx
             ) {
                 depth += depth_change;
                 continue;
+            }
             return SingleInferenceResult::Incompatible
+        }
         return if modified {
             to_infer.recompute_is_done();
             SingleInferenceResult::Modified
         } else {
             SingleInferenceResult::Unmodified
+        }
+    }
     /// Checks if both types are compatible, doesn't perform any inference
     fn check_subtrees(
         type_parts_a: &[InferenceTypePart], start_idx_a: usize,
         type_parts_b: &[InferenceTypePart], start_idx_b: usize
     ) -> bool {
         let mut depth = 1;
         let mut idx_a = start_idx_a;
         let mut idx_b = start_idx_b;
         while depth > 0 {
             let part_a = &type_parts_a[idx_a];
             let part_b = &type_parts_b[idx_b];
             if part_a == part_b {
                 let depth_change = part_a.depth_change();
                 depth += depth_change;
                 debug_assert_eq!(depth_change, part_b.depth_change());
                 idx_a += 1;
                 idx_b += 1;
                 continue;
+            }
             if part_a.is_marker() { idx_a += 1; continue; }
             if part_b.is_marker() { idx_b += 1; continue; }
             if let Some(depth_change) = Self::check_part_for_single_type(
                 type_parts_a, &mut idx_a, type_parts_b, &mut idx_b
             ) {
                 depth += depth_change;
                 continue;
+            }
             if let Some(depth_change) = Self::check_part_for_single_type(
                 type_parts_b, &mut idx_b, type_parts_a, &mut idx_a
             ) {
                 depth += depth_change;
                 continue;
+            }
             return false;
+        }
         true
+    }
     /// Performs the conversion of the inference type into a concrete type.
     /// By calling this function you must make sure that no unspecified types
     /// (e.g. Unknown or IntegerLike) exist in the type.
     fn write_concrete_type(&self, concrete_type: &mut ConcreteType) {
         use InferenceTypePart as ITP;
         use ConcreteTypePart as CTP;
         // Make sure inference type is specified but concrete type is not yet specified
         debug_assert!(!self.parts.is_empty());
         debug_assert!(concrete_type.parts.is_empty());
         concrete_type.parts.reserve(self.parts.len());
         let mut idx = 0;
         while idx < self.parts.len() {
             let part = &self.parts[idx];
             let converted_part = match part {
                 ITP::MarkerDefinition(marker) => {
                     // Outer markers are converted to regular markers, we
                     // completely remove the type subtree that follows it
                     idx = InferenceType::find_subtree_end_idx(&self.parts, idx + 1);
                     concrete_type.parts.push(CTP::Marker(*marker));
                     continue;
                 },
                 ITP::MarkerBody(_) => {
                     // Inner markers are removed when writing to the concrete
                     // type.
                     idx += 1;
                     continue;
                 },
                 ITP::Unknown | ITP::NumberLike | ITP::IntegerLike | ITP::ArrayLike | ITP::PortLike => {
                     unreachable!("Attempted to convert inference type part {:?} into concrete type", part);
                 },
                 ITP::Void => CTP::Void,
                 ITP::Message => CTP::Message,
                 ITP::Bool => CTP::Bool,
                 ITP::Byte => CTP::Byte,
                 ITP::Short => CTP::Short,
                 ITP::Int => CTP::Int,
                 ITP::Long => CTP::Long,
                 ITP::String => CTP::String,
                 ITP::Array => CTP::Array,
                 ITP::Slice => CTP::Slice,
                 ITP::Input => CTP::Input,
                 ITP::Output => CTP::Output,
                 ITP::Instance(id, num) => CTP::Instance(*id, *num),
             };
             concrete_type.parts.push(converted_part);
             idx += 1;
+        }
+    }
     /// Writes a human-readable version of the type to a string. Mostly a
     /// function for interior use.
     fn write_display_name(
         buffer: &mut String, heap: &Heap, parts: &[InferenceTypePart], mut idx: usize
     ) -> usize {
         use InferenceTypePart as ITP;
         match &parts[idx] {
             ITP::MarkerDefinition(_) | ITP::MarkerBody(_) => {
                 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_any(&self) -> bool {
         match self {
             DualInferenceResult::First | DualInferenceResult::Second | DualInferenceResult::Both => true,
             _ => false
+        }
+    }
     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,
     Component(ComponentId),
     Function(FunctionId),
+}
 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 function call 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(_) => {},
+            }
+        }
+    }
     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)?;
         self.progress_constant_expr(ctx, 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)?;
+                }
+            }
+        }
         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<(), ParseError2> {
         // 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)?;
+        }
         // Should have inferred everything. Check for this and optionally
         // auto-infer the remaining types
         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(ParseError2::new_error(
                         &ctx.module.source, expr.position(),
                         &format!(
                             "Could not fully infer the type of this expression (got '{}')",
                             expr_type.display_name(&ctx.heap)
+                        )
                     ))
+                }
+            }
             let concrete_type = ctx.heap[*expr_id].get_type_mut();
             expr_type.write_concrete_type(concrete_type);
+        }
         // Check all things we need to monomorphize
         // TODO: Struct/enum/union monomorphization
         for (call_expr_id, extra_data) in self.extra_data.iter() {
             if extra_data.poly_vars.is_empty() { continue; }
             // Retrieve polymorph variable specification
             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[*call_expr_id];
                     return Err(ParseError2::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 call expression's definition
             let call_expr = if let Expression::Call(call_expr) = &ctx.heap[*call_expr_id] {
                 call_expr
             } else {
                 todo!("implement different kinds of polymorph expressions");
             };
             // 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
                     ctx.types.add_monomorph(&definition_id, monomorph_types.clone());
                     queue.push(ResolveQueueElement {
                         root_id,
                         definition_id,
                         monomorph_types,
                     })
+                }
+            }
+        }
         Ok(())
+    }
     fn progress_expr(&mut self, ctx: &mut Ctx, id: ExpressionId) -> Result<(), ParseError2> {
         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_constant_expr(ctx, id)
+                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<(), ParseError2> {
         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<(), ParseError2> {
         // 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<(), ParseError2> {
         // 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<(), ParseError2> {
         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<(), ParseError2> {
         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<(), ParseError2> {
         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<(), ParseError2> {
         let upcast_id = id.upcast();
         let expr = &ctx.heap[id];
         let subject_id = expr.subject;
         debug_log!("Select expr: {}", upcast_id.index);
         debug_log!(" * Before:");
         debug_log!("   - Subject type: {}", self.expr_types.get(&subject_id).unwrap().display_name(&ctx.heap));
         debug_log!("   - Expr    type: {}", self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         let (progress_subject, progress_expr) = match &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) => {
                 todo!("implement select expr for symbolic fields");
             Field::Symbolic(field) => {
                 // Check if we already know the definition ID of the subject
                 let mut definition_and_field = None;
                 let subject_type = self.expr_types.get(&subject_id).unwrap();
                 'type_loop: for part in &subject_type.parts {
                     if part.is_marker() || !part.is_concrete() { continue; }
                     if let InferenceTypePart::Instance(definition_id, _) = part {
                         // Make sure we're accessing a struct of some sort
                         let definition_type = ctx.types.get_base_definition(definition_id).unwrap();
                         if let DefinedTypeVariant::Struct(definition) = &definition_type.definition {
                             // Make sure the struct has the specified field
                             let mut field_found = false;
                             for (def_field_idx, def_field) in definition.fields.iter().enumerate() {
                                 if def_field.identifier == *field {
                                     definition_and_field = Some((*definition_id, def_field_idx));
                                     break 'type_loop;
+                                }
+                            }
                             // If here then field was not found
                             if !field_found {
                                 let definition = &ctx.heap[*definition_id];
                                 return Err(ParseError2::new_error(
                                     &ctx.module.source, field.position,
                                     &format!(
                                         "The field '{}' does not exist on the struct '{}'",
                                         &String::from_utf8_lossy(&field.value),
                                         &String::from_utf8_lossy(&definition.identifier().value)
+                                    )
                                 ))
+                            }
+                        }
                         // Else, fall through and complain about not being a struct
+                    }
                     // Concrete part that is not an instance of a struct,
                     // select expression cannot possibly be correct
                     return Err(ParseError2::new_error(
                         &ctx.module.source, ctx.heap[subject_id].position(),
                         &format!(
                             "Expected to find a struct instance to access a field from, found a '{}'",
                             subject_type.display_name(&ctx.heap)
+                        )
                     ))
+                }
                 // If here then we have our definition and field idx
                 let (definition_id, field_idx) = definition_and_field.unwrap();
                 (false, false)
+            }
         };
         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));
         if progress_subject { self.queue_expr(subject_id); }
         if progress_expr { self.queue_expr_parent(ctx, upcast_id); }
         Ok(())
+    }
     fn progress_array_expr(&mut self, ctx: &mut Ctx, id: ArrayExpressionId) -> Result<(), ParseError2> {
         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_constant_expr(&mut self, ctx: &mut Ctx, id: LiteralExpressionId) -> Result<(), ParseError2> {
+    fn progress_literal_expr(&mut self, ctx: &mut Ctx, id: LiteralExpressionId) -> Result<(), ParseError2> {
         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();
                 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);
+                    }
+                }
                 // 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)
                 );
                 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(
                         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(
                     extra, &poly_progress, signature_type, expr_type
                 );
                 progress_expr
+            }
         };
         let progress = self.apply_forced_constraint(ctx, upcast_id, template)?;
         if progress { 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));
         // TODO: FIX!!!!
         if progress_expr { self.queue_expr_parent(ctx, upcast_id); }
         Ok(())
+    }
     // TODO: @cleanup, see how this can be cleaned up once I implement
     //  polymorphic struct/enum/union literals. These likely follow the same
     //  pattern as here.
     fn progress_call_expr(&mut self, ctx: &mut Ctx, id: CallExpressionId) -> Result<(), ParseError2> {
         let upcast_id = id.upcast();
         let expr = &ctx.heap[id];
         let extra = self.extra_data.get_mut(&upcast_id).unwrap();
         debug_log!("Call expr '{}': {}", match &expr.method {
             Method::Create => String::from("create"),
             Method::Fires => String::from("fires"),
             Method::Get => String::from("get"),
             Method::Put => String::from("put"),
             Method::Symbolic(method) => String::from_utf8_lossy(&method.identifier.value).to_string()
         },upcast_id.index);
         debug_log!(" * Before:");
         debug_log!("   - Expr type: {}", self.expr_types.get(&upcast_id).unwrap().display_name(&ctx.heap));
         debug_log!(" * During (inferring types from arguments and return type):");
         // Check if we can make progress using the arguments and/or return types
         // while keeping track of the polyvars we've extended
         let mut poly_progress = HashSet::new();
         debug_assert_eq!(extra.embedded.len(), expr.arguments.len());
         let mut poly_infer_error = false;
         for (arg_idx, arg_id) in expr.arguments.clone().into_iter().enumerate() {
             let signature_type = &mut extra.embedded[arg_idx];
+            let signature_type: *mut _ = &mut extra.embedded[arg_idx];
             let argument_type: *mut _ = self.expr_types.get_mut(&arg_id).unwrap();
             let (progress_sig, progress_arg) = Self::apply_equal2_signature_constraint(
                 ctx, upcast_id, Some(arg_id), signature_type, 0, argument_type, 0
             let (_, progress_arg) = Self::apply_equal2_signature_constraint(
                 ctx, upcast_id, Some(arg_id), extra, &mut poly_progress,
                 signature_type, 0, argument_type, 0
             )?;
             debug_log!("   - Arg {} type | sig: {}, arg: {}", arg_idx, signature_type.display_name(&ctx.heap), unsafe{&*argument_type}.display_name(&ctx.heap));
             if progress_sig {
                 // Progressed signature, so also apply inference to the
                 // polymorph types using the markers
                 debug_assert!(signature_type.has_body_marker, "progress on signature argument type without markers");
                 for (poly_idx, poly_section) in signature_type.body_marker_iter() {
                     let polymorph_type = &mut extra.poly_vars[poly_idx];
                     match Self::apply_forced_constraint_types(
                         polymorph_type, 0, poly_section, 0
                     ) {
                         Ok(true) => { poly_progress.insert(poly_idx); },
                         Ok(false) => {},
                         Err(()) => { poly_infer_error = true; }
+                    }
             debug_log!(
                 "   - Arg {} type | sig: {}, arg: {}", arg_idx,
                 unsafe{&*signature_type}.display_name(&ctx.heap),
                 unsafe{&*argument_type}.display_name(&ctx.heap));
                     debug_log!("   - Poly {} type | sig: {}, arg: {}", poly_idx, polymorph_type.display_name(&ctx.heap), InferenceType::partial_display_name(&ctx.heap, poly_section));
+                }
+            }
             if progress_arg {
                 // Progressed argument expression
                 self.expr_queued.insert(arg_id);
+            }
+        }
         // Do the same for the return type
         let signature_type = &mut extra.returned;
+        let signature_type: *mut _ = &mut extra.returned;
         let expr_type: *mut _ = self.expr_types.get_mut(&upcast_id).unwrap();
         let (progress_sig, progress_expr) = Self::apply_equal2_signature_constraint(
             ctx, upcast_id, None, signature_type, 0, expr_type, 0
         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: {}, arg: {}", signature_type.display_name(&ctx.heap), unsafe{&*expr_type}.display_name(&ctx.heap));
         debug_log!(
             "   - Ret type | sig: {}, expr: {}",
             unsafe{&*signature_type}.display_name(&ctx.heap),
             unsafe{&*expr_type}.display_name(&ctx.heap)
         );
         if progress_sig {
             // As above: apply inference to polyargs as well
             debug_assert!(signature_type.has_body_marker, "progress on signature return type without markers");
             for (poly_idx, poly_section) in signature_type.body_marker_iter() {
                 let polymorph_type = &mut extra.poly_vars[poly_idx];
                 match Self::apply_forced_constraint_types(
                     polymorph_type, 0, poly_section, 0
                 ) {
                     Ok(true) => { poly_progress.insert(poly_idx); },
                     Ok(false) => {},
                     Err(()) => { poly_infer_error = true; }
+                }
                 debug_log!("   - Poly {} type | sig: {}, arg: {}", poly_idx, polymorph_type.display_name(&ctx.heap), InferenceType::partial_display_name(&ctx.heap, poly_section));
+            }
+        }
         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 had an error in the polymorphic variable's inference, then we
         // need to provide a human readable error: find a pair of inference
         // types in the arguments/return type that do not agree on the
         // polymorphic variable's type
         if poly_infer_error { return Err(self.construct_poly_arg_error(ctx, 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 progress polyvars):");
+        debug_log!(" * During (reinferring from progressed polyvars):");
         // 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 poly_idx in poly_progress.into_iter() {
             // For each polymorphic argument: first extend the signature type,
             // then reapply the equal2 constraint to the expressions
             let poly_type = &extra.poly_vars[poly_idx];
             for (arg_idx, sig_type) in extra.embedded.iter_mut().enumerate() {
                 let mut seek_idx = 0;
                 let mut modified_sig = false;
                 while let Some((start_idx, end_idx)) = sig_type.find_subtree_idx_for_part(
                     InferenceTypePart::MarkerBody(poly_idx), seek_idx
                 ) {
                     let modified_at_marker = Self::apply_forced_constraint_types(
                         sig_type, start_idx, &poly_type.parts, 0
                     ).unwrap();
                     modified_sig = modified_sig || modified_at_marker;
                     seek_idx = end_idx;
+                }
                 if !modified_sig {
                     debug_log!("   - Poly {} | Arg {} type | signature has not changed", poly_idx, arg_idx);
                     continue;
+                }
                 // Part of signature was modified, so update expression used as
                 // argument as well
         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_signature_constraint(
                     ctx, arg_expr_id, Some(arg_expr_id), sig_type, 0, arg_type, 0
                 ).expect("no inference error at argument type");
                 if progress_arg { self.expr_queued.insert(arg_expr_id); }
                 debug_log!("   - Poly {} | Arg {} type | sig: {}, arg: {}", poly_idx, arg_idx, sig_type.display_name(&ctx.heap), unsafe{&*arg_type}.display_name(&ctx.heap));
+            }
             // Again: do the same for the return type
             let sig_type = &mut extra.returned;
             let mut seek_idx = 0;
             let mut modified_sig = false;
             while let Some((start_idx, end_idx)) = sig_type.find_subtree_idx_for_part(
                 InferenceTypePart::MarkerBody(poly_idx), seek_idx
             ) {
                 let modified_at_marker = Self::apply_forced_constraint_types(
                     sig_type, start_idx, &poly_type.parts, 0
                 ).unwrap();
                 modified_sig = modified_sig || modified_at_marker;
                 seek_idx = end_idx;
+            }
             let progress_arg = Self::apply_equal2_polyvar_constraint(
                 extra, &poly_progress,
                 signature_type, arg_type
             );
             if modified_sig {
                 let ret_type = self.expr_types.get_mut(&upcast_id).unwrap();
                 let (_, progress_ret) = Self::apply_equal2_signature_constraint(
                     ctx, upcast_id, None, sig_type, 0, ret_type, 0
                 ).expect("no inference error at return type");
                 if progress_ret {
                     if let Some(parent_id) = ctx.heap[upcast_id].parent_expr_id() {
                         self.expr_queued.insert(parent_id);
             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);
+            }
+        }
                 debug_log!("   - Poly {} | Ret type | sig: {}, arg: {}", poly_idx, sig_type.display_name(&ctx.heap), ret_type.display_name(&ctx.heap));
             } else {
                 debug_log!("   - Poly {} | Ret type | signature has not changed", poly_idx);
+            }
         // 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(
             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<(), ParseError2> {
         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(ParseError2::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(ParseError2::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, ParseError2> {
         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), ParseError2> {
         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), ParseError2> {
         // 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 => ("return type's", outer_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(ParseError2::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
+                )
             ));
+        }
         Ok((infer_res.modified_lhs(), infer_res.modified_rhs()))
         // 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(
         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 seek_idx < signature_type.parts.len() {
             if let InferenceTypePart::MarkerBody(poly_idx) = &signature_type.parts[seek_idx] {
                 let poly_idx = *poly_idx;
                 if polymorph_progress.contains(&poly_idx) {
                     // Need to match subtrees
                     let polymorph_type = &polymorph_data.poly_vars[poly_idx];
                     let start_idx = seek_idx + 1;
                     let end_idx = InferenceType::find_subtree_end_idx(&signature_type.parts, start_idx);
                     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;
                     continue;
+                }
+            }
             seek_idx += 1;
+        }
         // 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), ParseError2> {
         // 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>, ParseError2> {
         // 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.
     /// Hence: if the expression type is already set, this function doesn't do
     /// anything.
     fn insert_initial_expr_inference_type(
         &mut self, ctx: &mut Ctx, expr_id: ExpressionId
     ) -> Result<(), ParseError2> {
         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!(poly_vars.len(), definition.poly_vars.len());
+                        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(_) => {
                         unreachable!("insert initial polymorph data for struct/enum");
+                    }
+                }
+            }
         };
         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_args.len());
         let mut total_num_poly_parts = 0;
         for poly_arg_type_id in literal.poly_args.clone() { // TODO: @performance
             poly_vars.push(self.determine_inference_type_from_parser_type(ctx, *poly_arg_type_id, true))
             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()];
         match definition {
+        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 programmer-
         // 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());
+        }
         // TODO: Continue here!!!
         debug_assert_eq!(parts.len(), parts_reserved);
         let return_type = InferenceType::new(true, return_type_done, parts);
         self.extra_data.insert(lit_id.upcast(), ExtraData{
             poly_vars,
             embedded: embedded_types,
             returned: return_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_args.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
                                 let num_poly = match definition {
                                     Definition::Struct(v) => v.poly_vars.len(),
                                     Definition::Enum(v) => v.poly_vars.len(),
                                     _ => unreachable!(),
                                 };
                                 debug_assert_eq!(symbolic.poly_args.len(), num_poly);
+                            }
                             infer_type.push(ITP::Instance(*definition_id, symbolic.poly_args.len()));
                             let mut poly_arg_idx = symbolic.poly_args.len();
                             while poly_arg_idx > 0 {
                                 poly_arg_idx -= 1;
                                 to_consider.push_front(symbolic.poly_args[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
     ) -> ParseError2 {
         // 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 ParseError2::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
     ) -> ParseError2 {
         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 ParseError2::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]
     ) -> ParseError2 {
         let expr = &ctx.heap[expr_id];
         let expr_type = self.expr_types.get(&expr_id).unwrap();
         return ParseError2::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 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.
     /// 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 (which may be a argument type or return type
     /// conflicting with itself) and construct the error using it.
     /// 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(
-        &self, ctx: &Ctx, call_id: CallExpressionId
+        ctx: &Ctx, poly_data: &ExtraData, expr_id: ExpressionId
     ) -> ParseError2 {
         // 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 function name
+        // 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(_) => 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_literal_name(ctx: &Ctx, poly_var_idx: usize, expr: &LiteralExpression) -> (String, String) {
             let expr = expr.value.as_struct();
             let definition = &ctx.heap[expr.definition.unwrap()];
             match definition {
                 Definition::Enum(_) | Definition::Function(_) | Definition::Component(_) =>
                     unreachable!(),
                 Definition::Struct(definition) => (
                     String::from_utf8_lossy(&definition.poly_vars[poly_var_idx].value).to_string(),
                     String::from_utf8_lossy(&definition.identifier.value).to_string()
                 ),
+            }
+        }
         // Helper function to construct initial error
         fn construct_main_error(ctx: &Ctx, poly_var_idx: usize, expr: &CallExpression) -> ParseError2 {
         fn construct_main_error(ctx: &Ctx, poly_var_idx: usize, expr: &Expression) -> ParseError2 {
             match expr {
                 Expression::Call(expr) => {
                     let (poly_var, func_name) = get_poly_var_and_func_name(ctx, poly_var_idx, expr);
                     return ParseError2::new_error(
                         &ctx.module.source, expr.position(),
                         &format!(
                             "Conflicting type for polymorphic variable '{}' of '{}'",
                             poly_var, func_name
+                        )
+                    )
                 },
                 Expression::Literal(expr) => {
                     let (poly_var, struct_name) = get_poly_var_and_literal_name(ctx, poly_var_idx, expr);
                     return ParseError2::new_error(
                         &ctx.module.source, expr.position(),
                         &format!(
                             "Conflicting type for polymorphic variable '{}' of instantiation of '{}'",
                             poly_var, struct_name
+                        )
+                    )
                 },
                 _ => unreachable!("called construct_poly_arg_error without a call/literal expression")
+            }
+        }
         // Actual checking
         let extra = self.extra_data.get(&call_id.upcast()).unwrap();
         let expr = &ctx.heap[call_id];
         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) =>
+                (
                     expr.value.as_struct().fields
                         .iter()
                         .map(|f| f.value)
                         .collect(),
                     "literal"
                 ),
             _ => unreachable!(),
         };
         // - check return type with itself
         if let Some((poly_idx, section_a, section_b)) = has_poly_mismatch(&extra.returned, &extra.returned) {
         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 return type inferred the conflicting types '{}' and '{}'",
                         "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 extra.embedded.iter().enumerate() {
             for (arg_b_idx, arg_b) in extra.embedded.iter().enumerate() {
         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.arguments[arg_a_idx]];
+                        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.arguments[arg_a_idx]];
                         let arg_b = &ctx.heap[expr.arguments[arg_b_idx]];
                         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, &extra.returned) {
                 let arg = &ctx.heap[expr.arguments[arg_a_idx]];
             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,
+                        &ctx.module.source, expr.position(),
                         &format!(
                             "While the return type inferred it to '{}'",
                             "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, false, 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, false, 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)
+        }
+    }
+}
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