From bfc78e77ae7937925cb8103a4de361568c53b71f Mon Sep 17 00:00:00 2001
From: hauntsaninja <>
Date: Sun, 27 Sep 2020 23:58:34 -0700
Subject: [PATCH 1/3] Fix partial type crash during protocol checking

In particular, this affected hashables.
---
 mypy/subtypes.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mypy/subtypes.py b/mypy/subtypes.py
index 107a5abbebab..81726b1f9884 100644
--- a/mypy/subtypes.py
+++ b/mypy/subtypes.py
@@ -543,6 +543,10 @@ def f(self) -> A: ...
             # print(member, 'of', right, 'has type', supertype)
             if not subtype:
                 return False
+            if isinstance(subtype, PartialType):
+                subtype = NoneType() if subtype.type is None else Instance(
+                    subtype.type, [AnyType(TypeOfAny.unannotated)] * len(subtype.type.type_vars)
+                )
             if not proper_subtype:
                 # Nominal check currently ignores arg names
                 # NOTE: If we ever change this, be sure to also change the call to

From 43d587202ec0a55a133422906523742f8f69f229 Mon Sep 17 00:00:00 2001
From: hauntsaninja <>
Date: Mon, 28 Sep 2020 18:39:24 -0700
Subject: [PATCH 2/3] add tests

---
 test-data/unit/check-protocols.test | 35 +++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/test-data/unit/check-protocols.test b/test-data/unit/check-protocols.test
index 0c0865c0540e..447be4848dd5 100644
--- a/test-data/unit/check-protocols.test
+++ b/test-data/unit/check-protocols.test
@@ -2536,3 +2536,38 @@ class EmptyProto(Protocol): ...
 def hh(h: EmptyProto) -> None: pass
 hh(None)
 [builtins fixtures/tuple.pyi]
+
+
+[case testPartialTypeProtocol]
+from typing import Protocol
+
+class Flapper(Protocol):
+    def flap(self) -> int: ...
+
+class Blooper:
+    flap = None
+
+    def bloop(self, x: Flapper) -> None:
+        reveal_type([self, x])  # N: Revealed type is 'builtins.list[builtins.object*]'
+
+class Gleemer:
+    flap = []  # E: Need type annotation for 'flap' (hint: "flap: List[<type>] = ...")
+
+    def gleem(self, x: Flapper) -> None:
+        reveal_type([self, x])  # N: Revealed type is 'builtins.list[builtins.object*]'
+[builtins fixtures/tuple.pyi]
+
+
+[case testPartialTypeProtocolHashable]
+# flags: --strict-optional
+from typing import Protocol
+
+class Hashable(Protocol):
+    def __hash__(self) -> int: ...
+
+class DataArray:
+    __hash__ = None
+
+    def f(self, x: Hashable) -> None:
+        reveal_type([self, x])  # N: Revealed type is 'builtins.list[builtins.object*]'
+[builtins fixtures/tuple.pyi]
\ No newline at end of file

From 85e301e5046880086349e930d276e4cb7b296607 Mon Sep 17 00:00:00 2001
From: hauntsaninja <>
Date: Mon, 28 Sep 2020 19:57:07 -0700
Subject: [PATCH 3/3] Fix up testPartialTypeProtocolHashable

This test case was meant to use `--no-strict-optional`, not
`--strict-optional`, but happened to crash anyway because object in the
test stubs doesn't have __hash__. Both changes made.
---
 test-data/unit/check-protocols.test | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/test-data/unit/check-protocols.test b/test-data/unit/check-protocols.test
index 447be4848dd5..30d33b917123 100644
--- a/test-data/unit/check-protocols.test
+++ b/test-data/unit/check-protocols.test
@@ -2559,15 +2559,18 @@ class Gleemer:
 
 
 [case testPartialTypeProtocolHashable]
-# flags: --strict-optional
+# flags: --no-strict-optional
 from typing import Protocol
 
 class Hashable(Protocol):
     def __hash__(self) -> int: ...
 
-class DataArray:
+class ObjectHashable:
+    def __hash__(self) -> int: ...
+
+class DataArray(ObjectHashable):
     __hash__ = None
 
     def f(self, x: Hashable) -> None:
         reveal_type([self, x])  # N: Revealed type is 'builtins.list[builtins.object*]'
-[builtins fixtures/tuple.pyi]
\ No newline at end of file
+[builtins fixtures/tuple.pyi]