Compiler: Start implementing the type checker

Compiler/Ast.fir

@@ -1,6 +1,7 @@
 import [
     Compiler/Defs,
     Compiler/Token,
+    Compiler/TypeCheck/Ty,
 ]
 
 
@@ -98,18 +99,6 @@ type ConDecl(
 )
 
 
-#[derive(ToDoc)]
-type Kind:
-    Star
-    Row(RecordOrVariant)
-
-
-#[derive(ToDoc)]
-type RecordOrVariant:
-    Record
-    Variant
-
-
 #[derive(ToDoc)]
 type ConFields:
     Empty
@@ -194,10 +183,10 @@ type TraitDecl(
 ##
 ## ```
 ## impl[ToStr[a]] ToStr[Vec[a]]:
-##   toStr(self): Str = ...
+##   toStr(self) Str: ...
 ##
 ## impl Iterator[VecIter[a], a]:
-##   next(self): Option[a] = ...
+##   next(self) Option[a]: ...
 ## ```
 #[derive(ToDoc)]
 type ImplDecl(
@@ -384,6 +373,12 @@ type NamedType(
 )
 
 
+NamedType.numTyArgs(self) U32:
+    match self.args:
+        Option.None: 0
+        Option.Some(args): args.args.len()
+
+
 impl Tokens[NamedType]:
     firstToken(self: NamedType) TokenIdx:
         self.name.token
@@ -499,14 +494,12 @@ type ForStmt(
     astTy: Option[Type],
 
     ## `ast_ty`, converted to type checking types by the type checker.
-    tcTy: Option[Type], # TODO: type-checking type
-
+    tcTy: Option[Ty],
 
     expr: Expr,
 
     ## Filled in by the type checker: the iterator type. `iter` in `Iterator[iter, item]`.
-    exprTy: Option[Type], # TODO: type-checking type
-
+    exprTy: Option[Ty],
 
     body: Vec[Stmt],
 
@@ -651,8 +644,7 @@ type VarPat(
     var_: Id,
 
     ## Inferred type of the binder. Filled in by the type checker.
-    ty: Option[Type], # TODO: This should be type-checking type instead of AST type
-
+    ty: Option[Ty],
 )
 
 
@@ -685,9 +677,7 @@ impl Tokens[ConstrPat]:
 type RecordPat(
     fields: Vec[Named[Pat]],
     ignoreRest: Bool,
-
-    # TODO: This should be type-checking type instead of AST type
-    inferredTy: Option[Type],
+    inferredTy: Option[Ty],
     _firstToken: TokenIdx,
     _lastToken: TokenIdx,
 )
@@ -947,8 +937,7 @@ type MethodSelectExpr(
     # TODO: We could also add types to every expression if it's going to help with monomorphisation.
     #       For efficiency though, we should only annotate inferred types and then type check from
     #       the top-level expression every time we need to compute type of an expr.
-    # TODO: This should be a type-checking type.
-    objectTy: Option[Type],
+    objectTy: Option[Ty],
 
     ## The type or trait id that defines the method.
     ##
@@ -964,14 +953,13 @@ type MethodSelectExpr(
 
     ## Type arguments of `method_ty_id`.
     ##
-    ## If the method is for a trait, the first arguments here will be for the trait type parameters.
-    ## E.g. in `Iterator.next`, the first two argumetns will be the `iter` and `item` parameters of
-    ## `trait Iterator[iter, item]`.
+    ## If the method is for a trait, the first arguments here will be for the
+    ## trait type parameters. E.g. in `Iterator.next`, the first two argumetns
+    ## will be the `iter` and `item` parameters of `trait Iterator[iter, item]`.
     ##
-    ## (If the method is not a trait method, then we don't care about the type parameter order.. I
-    ## think?)
-    tyArgs: Vec[Type], # TODO: type-checking type
-
+    ## (If the method is not a trait method, then we don't care about the type
+    ## parameter order.. I think?)
+    tyArgs: Vec[Ty],
 
     _lastToken: TokenIdx,
 )
@@ -1001,9 +989,9 @@ type AssocFnSelectExpr(
     ## Type arguments explicitly passed to the variable.
     userTyArgs: Option[TyArgs],
 
-    ## Inferred type arguments of the type and associated function. Filled in by the type checker.
-    tyArgs: Vec[Type], # TODO: type-checking type
-
+    ## Inferred type arguments of the type and associated function. Filled in by
+    ## the type checker.
+    tyArgs: Vec[Ty],
 
     _lastToken: TokenIdx,
 )
@@ -1506,24 +1494,6 @@ impl ToDoc[ConDecl]:
         Doc.grouped(Doc.str("ConDecl") + Doc.char('(') + args)
 
 
-impl ToDoc[Kind]:
-    toDoc(self: Kind) Doc:
-        match self:
-            Kind.Star: Doc.str("Kind.Star")
-            Kind.Row(i0):
-                let args = Doc.break_(0)
-                args += i0.toDoc()
-                args = args.nest(4).group() + Doc.break_(0) + Doc.char(')')
-                Doc.grouped(Doc.str("Kind.Row") + Doc.char('(') + args)
-
-
-impl ToDoc[RecordOrVariant]:
-    toDoc(self: RecordOrVariant) Doc:
-        match self:
-            RecordOrVariant.Record: Doc.str("RecordOrVariant.Record")
-            RecordOrVariant.Variant: Doc.str("RecordOrVariant.Variant")
-
-
 impl ToDoc[ConFields]:
     toDoc(self: ConFields) Doc:
         match self: