fixed inheritance check

toy-impl/inheritance.py

@@ -14,11 +14,20 @@ def class_fixup(c: ClassType):
             if m in c.methods:
                 old = p.methods[m]
                 new = c.methods[m]
-                if old[0] != new[0] or old[1] != new[1]:
+                for a, b in zip(old[0], new[0]):
+                    if a != b:
+                        raise CustomError(f'{m} is different in {c.name} and {p.name}')
+                if old[1] != new[1]:
                     # actually, we should check for equality *modulo variable renaming*
-                    raise CustomError(f'incorrect method signature for {m} in {c.name}')
+                    raise CustomError(f'{m} is different in {c.name} and {p.name}')
             else:
                 c.methods[m] = p.methods[m]
+        for f in p.fields:
+            if f in c.fields:
+                if p.fields[f] != c.fields[f]:
+                    raise CustomError(f'{f} is different in {c.name} and {p.name}')
+            else:
+                c.fields[f] = p.fields[f]
     c.checking = False
     c.checked = True
 

toy-impl/main.py

@@ -1,10 +1,11 @@
 import ast
 import sys
 from helper import CustomError
-from type_def import SelfType
+from type_def import SelfType, ClassType
 from parse_stmt import parse_stmts
 from primitives import simplest_ctx
 from top_level import parse_top_level
+from inheritance import class_fixup
 
 if len(sys.argv)  != 2:
     print('please pass the python script name as argument')
@@ -17,6 +18,10 @@ tree = ast.parse(source, filename=sys.argv[1])
 
 try:
     ctx, fns = parse_top_level(simplest_ctx, tree)
+    for c in ctx.types.values():
+        if isinstance(c, ClassType):
+            class_fixup(c)
+
     for c, name, fn in fns:
         if c is None:
             params, result, _ = ctx.functions[name]

toy-impl/parse_stmt.py

@@ -199,6 +199,11 @@ def parse_return_stmt(ctx: Context,
             raise CustomError('no return value is allowed', node)
         return {}, {}, True
     ty = parse_expr(ctx, sym_table, node.value)
+    if isinstance(node.value, ast.Name) and \
+            node.value.id == 'self' and \
+            'self' in sym_table and \
+            isinstance(return_ty, SelfType):
+        return {}, {}, True
     if ty != return_ty:
         if isinstance(return_ty, TypeVariable):
             if len(return_ty.constraints) == 1 and \

toy-impl/type_def.py

@@ -94,6 +94,9 @@ class SelfType(Type):
     def __str__(self):
         return 'self'
 
+    def __eq__(self, other):
+        return type(self) == type(other)
+
 
 class VirtualClassType(Type):
     base: ClassType