fixed bot type

toy-impl/inference.py

@@ -18,11 +18,17 @@ def find_subst(ctx: dict[str, Type],
     if isinstance(a, TypeVariable) and a.name in ctx:
         a = ctx[a.name]
 
+    if isinstance(a, BotType):
+        return sub
+
     if isinstance(b, TypeVariable):
         if b.name in sub:
             b = sub[b.name]
         else:
             if len(b.constraints) > 0:
+                # we cannot handle BotType correctly
+                # but that would not be a problem, as the user cannot get
+                # BotType in normal circumstances.
                 if isinstance(a, TypeVariable):
                     if len(a.constraints) == 0:
                         return f"{b} cannot take value of an unconstrained variable {a}"
@@ -42,8 +48,6 @@ def find_subst(ctx: dict[str, Type],
         else:
             return f"{a} can take values other than {b}"
 
-    if isinstance(a, BotType):
-        return sub
     # TODO: virtual type is not handled currently
     # we need to access the class dictionary to handle this
     if type(a) == type(b):

toy-impl/test_expr.py

@@ -95,8 +95,13 @@ class Foo:
 
     def __ge__(self, other: Foo) -> bool:
         pass
+
+def find(ls: list[I], x: I) -> int32:
+    pass
 """
 ctx, _ = parse_top_level(ctx, ast.parse(test_classes))
 test_expr('Foo(1) + Foo(1)', {})
 test_expr('Foo(1) + Foo(1) < Foo(2) + Foo(3) < Foo(4)', {})
+test_expr('find([1, 2, 3], 1)', {})
+test_expr('find([], 1)', {})
 

toy-impl/top_level.py

@@ -125,13 +125,13 @@ def parse_top_level(ctx: Context, module: ast.Module):
             function_stmts += parse_class(ctx, element)
         elif isinstance(element, ast.FunctionDef):
             name = element.name
-            if name in functions:
+            if name in ctx.functions:
                 raise CustomError(f"Duplicated function name {name}")
             if name in ctx.types:
                 raise CustomError(f"Function name {name} clashed with type name")
             args, result, var = parse_function(ctx, None, element)
             ctx.functions[name] = (args, result, var)
-            function_stmts += element
+            function_stmts.append(element)
 
     return ctx, function_stmts