From 3e4a79028c84e51ca5039be15ba2aeed65bdb7e7 Mon Sep 17 00:00:00 2001
From: Shannon Zhu <szhu@fb.com>
Date: Wed, 16 Sep 2020 11:12:06 -0700
Subject: [PATCH] Fix t.Set undefined type spurious error

Summary:
Looks like the latest binary release has fixed one part of the original issue - previously, `from typing import Set` would not throw this spurious error while `import typing as t` and referencing `t.Set` would.

Now, it's boiled down to a pretty clear issue where we are looking up the annotation `typing.Set` and cannot find it in the type hierarchy.

Looking a little closer, we `typing.Set` is not in our class hierarchy because `set` is, and we map the equivalence for other types like `typing.List -> list` in Type create. Adding this mapping fixes this issue.

typing.pyi: https://github.com/python/typeshed/blob/master/stdlib/3/typing.pyi
class hierarchy from env with typeshed included: P142551722

Reviewed By: grievejia

Differential Revision: D23726491

fbshipit-source-id: 15db093f5be6222b02ff4c4f3ae7ba221c3d82fc
---
 analysis/test/integration/annotationTest.ml | 9 +++++++++
 analysis/test/typeTest.ml                   | 1 +
 analysis/type.ml                            | 1 +
 3 files changed, 11 insertions(+)

diff --git a/analysis/test/integration/annotationTest.ml b/analysis/test/integration/annotationTest.ml
index fc606abd943..6f37c283de5 100644
--- a/analysis/test/integration/annotationTest.ml
+++ b/analysis/test/integration/annotationTest.ml
@@ -169,6 +169,15 @@ let test_check_undefined_type context =
       "Unbound name [10]: Name `Herp` is used but not defined in the current scope.";
     ];
 
+  assert_strict_type_errors
+    {|
+      import typing as t
+
+      def foo() -> t.Set:
+        return set()
+    |}
+    ["Invalid type parameters [24]: Generic type `set` expects 1 type parameter."];
+
   (* Attributes *)
   assert_type_errors
     {|
diff --git a/analysis/test/typeTest.ml b/analysis/test/typeTest.ml
index f0029931f3b..cc88bd194ae 100644
--- a/analysis/test/typeTest.ml
+++ b/analysis/test/typeTest.ml
@@ -127,6 +127,7 @@ let test_create _ =
   (* Check renaming. *)
   assert_create "typing.List[int]" (Type.list Type.integer);
   assert_create "typing.List" (Primitive "list");
+  assert_create "typing.Set" (Primitive "set");
   assert_create
     "typing.DefaultDict[int, str]"
     (Type.parametric "collections.defaultdict" ![Type.integer; Type.string]);
diff --git a/analysis/type.ml b/analysis/type.ml
index eee3744e846..e6bb39f4dbf 100644
--- a/analysis/type.ml
+++ b/analysis/type.ml
@@ -2276,6 +2276,7 @@ let primitive_substitution_map =
     "typing.Dict", Primitive "dict";
     "typing.List", Primitive "list";
     "typing.OrderedDict", Primitive "collections.OrderedDict";
+    "typing.Set", Primitive "set";
     "typing.Tuple", Primitive "tuple";
     "typing.Type", Primitive "type";
     "typing_extensions.Protocol", Primitive "typing.Protocol";