Fix ParamSpec bug in typecheck

Summary:
We create a new version of parse_annotation that accepts scoped type variables.

We can collect type variables from resolution generally speaking and then turn them into a scope.

What concerns me is that there are still places in the typechecker that still don't do that. I think overtime I need to observe user reports and put more unittests after variance.

So far, I've fixed the bugs that

Reviewed By: stroxler

Differential Revision: D63868697

fbshipit-source-id: 001afe8f8aea56bed980c90033f3b51c1a80cb37

source/analysis/globalResolution.ml

@@ -237,6 +237,16 @@ let parse_annotation ({ dependency; _ } as resolution) =
     ~scoped_type_variables:None
 
 
+let parse_annotation_with_scoped_typed_variables
+    ({ dependency; _ } as resolution)
+    ~scoped_type_variables
+  =
+  AttributeResolution.ReadOnly.parse_annotation
+    ?dependency
+    (attribute_resolution resolution)
+    ~scoped_type_variables
+
+
 let global ({ dependency; _ } as resolution) =
   AttributeResolution.ReadOnly.global (attribute_resolution resolution) ?dependency
 

source/analysis/globalResolution.mli

@@ -94,6 +94,13 @@ val parse_annotation
   Expression.t ->
   Type.t
 
+val parse_annotation_with_scoped_typed_variables
+  :  t ->
+  scoped_type_variables:Type.Variable.t Identifier.Map.t option ->
+  ?validation:AttributeResolution.type_validation_policy ->
+  Expression.expression Node.t ->
+  Type.t
+
 val global : t -> Reference.t -> AttributeResolution.Global.t option
 
 val get_typed_dictionary : t -> Type.t -> Type.TypedDictionary.t option

source/analysis/test/integration/typeVariableTest.ml

@@ -67,7 +67,7 @@ let test_type_variable_scoping =
             def decorator3[**L, M](x: Callable[L, M]) -> int:
                 ...
             |}
-           ["Invalid type [31]: Expression `typing.Callable[(L, M)]` is not a valid type."];
+           [];
       (* PEP695 generic methods from non-generic classes *)
       labeled_test_case __FUNCTION__ __LINE__
       @@ assert_type_errors

source/analysis/typeCheck.ml

@@ -97,6 +97,26 @@ module type Signature = sig
   include Fixpoint.State with type t := t
 end
 
+(* A helper function which converts type parameters to a type variable map *)
+let scoped_type_variables_as_map scoped_type_variables_list =
+  let empty_string_map = Identifier.Map.empty in
+  let update_map map key value =
+    match Map.add ~key ~data:value map with
+    | `Ok new_map -> new_map
+    | `Duplicate -> map
+  in
+  let named_values = List.map ~f:(fun x -> Type.Variable.name x, x) scoped_type_variables_list in
+  let create_mapping_from_type_variable_assoc_list =
+    List.fold_left
+      ~f:(fun map (key, value) -> update_map map key value)
+      ~init:empty_string_map
+      named_values
+  in
+  match named_values with
+  | [] -> None
+  | _ -> Some create_mapping_from_type_variable_assoc_list
+
+
 let error_and_location_from_typed_dictionary_mismatch
     { Node.value = mismatch; location = define_location }
   =
@@ -636,8 +656,13 @@ module State (Context : Context) = struct
       else
         errors, Type.Top
     in
+    let type_variables_in_scope = Resolution.all_type_variables_in_scope resolution in
+    let scoped_type_variables = scoped_type_variables_as_map type_variables_in_scope in
     let annotation =
-      GlobalResolution.parse_annotation ~validation:NoValidation global_resolution expression
+      (GlobalResolution.parse_annotation_with_scoped_typed_variables ~scoped_type_variables)
+        ~validation:NoValidation
+        global_resolution
+        expression
     in
     let errors =
       match annotation with
@@ -6551,6 +6576,7 @@ module State (Context : Context) = struct
     let global_resolution = Resolution.global_resolution resolution in
     (* collect type parameters for functions *)
     let type_params, _ = get_type_params_as_variables type_params global_resolution in
+    let scoped_type_variables = scoped_type_variables_as_map type_params in
     (* Add them to the resolution *)
     let resolution =
       type_params
@@ -6715,7 +6741,9 @@ module State (Context : Context) = struct
             if String.is_prefix ~prefix:"**" name then
               match
                 annotation
-                >>| GlobalResolution.parse_annotation global_resolution
+                >>| GlobalResolution.parse_annotation_with_scoped_typed_variables
+                      global_resolution
+                      ~scoped_type_variables
                 >>| Type.unpack_value
                 |> Option.value ~default:None
                 >>| GlobalResolution.get_typed_dictionary global_resolution