fixed bugs in impl

toy-impl/test_top_level.py

@@ -5,7 +5,7 @@ from top_level import *
 test = """
 class A:
     a: int
-    def foo(a: B) -> int:
+    def foo(a: B):
         pass
 
 class B(A):

toy-impl/top_level.py

@@ -16,7 +16,7 @@ class Context:
 
 def parse_type(ctx: Context, ty):
     if ty is None:
-        return None
+        return None, set()
     elif isinstance(ty, ast.Name):
         if ty.id in ctx.types:
             return ctx.types[ty.id], set()
@@ -52,6 +52,8 @@ def parse_type(ctx: Context, ty):
             return VirtualClassType(param), var
         else:
             raise CustomError(f"Unknown Generic Type {ty.value}")
+    else:
+        raise CustomError(f"Unrecognized Type {ty}")
 
 
 def parse_function(ctx: Context, base, fn: ast.FunctionDef):