Fix ParamSpec bug where we do not propagate type vars in typecheck

Summary:
I'm going to try migrating some of IG's code. In the process, I found a bug where we do not properly propagate type vars in defines.

Specifically, we need to collect the type variables from PEP695 in the typechecker in various places, and there was a place where did not do that. If we do not collect them, the parser will return "unknown" giving incorrect typechecking results.

I added a legacy example as well to show that they both have the correct behavior and are matching (modulo qualification).

Note: the bug I got on IG was actually just "invalid syntax". Here's the diff with the error msg D65066009. This is strange though, since that sound like a parsing error and we should not be getting those.

Reviewed By: grievejia

Differential Revision: D65078436

fbshipit-source-id: b8e297ba24751bea85f0ab173775a8bb1b560a19

source/analysis/test/integration/typeVariableTest.ml

@@ -57,8 +57,6 @@ let test_type_variable_scoping =
 
             |}
            [];
-      (* TODO migeedz: Why do we need to express the domain of Callable as a list for this to
-         typecheck? *)
       labeled_test_case __FUNCTION__ __LINE__
       @@ assert_type_errors
            {|
@@ -68,6 +66,39 @@ let test_type_variable_scoping =
                 ...
             |}
            [];
+      labeled_test_case __FUNCTION__ __LINE__
+      @@ assert_type_errors
+           {|
+            from typing import Callable, Awaitable
+
+            def outer[**TParams, TReturn](
+                inner: Callable[TParams, Awaitable[TReturn]],
+            ) -> Callable[TParams, Awaitable[TReturn]]:
+                async def _func(
+                    *args: TParams.args, **kwargs: TParams.kwargs
+                ) -> TReturn:
+                    return await inner(*args, **kwargs)
+                return _func
+            |}
+           [];
+      labeled_test_case __FUNCTION__ __LINE__
+      @@ assert_type_errors
+           {|
+            from typing import Callable, Awaitable, ParamSpec, TypeVar
+
+            TParams = ParamSpec("TParams")
+            TReturn = TypeVar("TReturn")
+
+            def outer(
+                inner: Callable[TParams, Awaitable[TReturn]],
+            ) -> Callable[TParams, Awaitable[TReturn]]:
+                async def _func(
+                    *args: TParams.args, **kwargs: TParams.kwargs
+                ) -> TReturn:
+                    return await inner(*args, **kwargs)
+                return _func
+            |}
+           [];
       (* PEP695 generic methods from non-generic classes *)
       labeled_test_case __FUNCTION__ __LINE__
       @@ assert_type_errors

source/analysis/typeCheck.ml

@@ -481,7 +481,6 @@ module State (Context : Context) = struct
 
   let get_type_params_as_variables type_params global_resolution =
     let create_type = GlobalResolution.parse_annotation global_resolution in
-    (* TODO migeedz: why does parse_annotation return Top for types of the form A[int]? . *)
     let validate_bound bound =
       match bound.Node.value with
       | Expression.Tuple elements ->
@@ -6141,6 +6140,15 @@ module State (Context : Context) = struct
         in
         Value resolution, validate_return expression ~resolution ~errors ~actual ~is_implicit
     | Define { signature = { Define.Signature.name; parent; type_params; _ } as signature; _ } ->
+        let type_params, type_params_errors =
+          get_type_params_as_variables type_params global_resolution
+        in
+        let resolution =
+          type_params
+          |> List.fold ~init:resolution ~f:(fun resolution variable ->
+                 Resolution.add_type_variable resolution ~variable)
+        in
+
         let resolution =
           match parent with
           | NestingContext.Function _ ->
@@ -6152,7 +6160,6 @@ module State (Context : Context) = struct
               Resolution.new_local resolution ~reference:name ~type_info:annotation
           | _ -> resolution
         in
-        let _, type_params_errors = get_type_params_as_variables type_params global_resolution in
         Value resolution, type_params_errors
     | Import { Import.from; imports } ->
         let get_export_kind = function
@@ -6990,7 +6997,15 @@ module State (Context : Context) = struct
           |> add_typeguard_error return_annotation return_type
     in
     let add_capture_annotations ~outer_scope_type_variables resolution errors =
-      let process_signature ({ Define.Signature.parent; _ } as signature) =
+      let process_signature ({ Define.Signature.parent; type_params; _ } as signature) =
+        let type_params, _ = get_type_params_as_variables type_params global_resolution in
+
+        let resolution =
+          type_params
+          |> List.fold ~init:resolution ~f:(fun resolution variable ->
+                 Resolution.add_type_variable resolution ~variable)
+        in
+
         match parent with
         | NestingContext.Function _ ->
             type_of_signature ~module_name:Context.qualifier ~resolution signature
@@ -8060,7 +8075,12 @@ module State (Context : Context) = struct
         >>| List.map ~f:extract
         |> Option.value ~default:[]
       in
-      let type_variables_of_define signature_of_nesting_function =
+      let type_variables_of_define
+          ({ Define.Signature.type_params; _ } as signature_of_nesting_function)
+        =
+        let local_scope_function_type_params, _ =
+          get_type_params_as_variables type_params global_resolution
+        in
         let parser = GlobalResolution.nonvalidating_annotation_parser global_resolution in
         let generic_parameters_as_variables =
           GlobalResolution.generic_parameters_as_variables global_resolution
@@ -8074,6 +8094,7 @@ module State (Context : Context) = struct
           |> Type.Variable.all_free_variables
           |> List.dedup_and_sort ~compare:Type.Variable.compare
         in
+        let define_variables = define_variables @ local_scope_function_type_params in
         let containing_class_variables =
           (* PEP484 specifies that scope of the type variables of the outer class doesn't cover the
              inner one. We are able to inspect only 1 level of nesting class as a result. *)