From c93c3dfadb2bface82c415e238ec69a87bcc5c4e Mon Sep 17 00:00:00 2001
From: Kamil Turek <kamil.turek@hotmail.com>
Date: Thu, 8 Apr 2021 23:11:02 +0200
Subject: [PATCH 1/2] Issue an error when overriding typeguard with
 non-typeguard in subclass

---
 mypy/checker.py                     | 3 +++
 test-data/unit/check-typeguard.test | 4 ++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/mypy/checker.py b/mypy/checker.py
index fce7e7d7a08e..50b503989800 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -1610,6 +1610,9 @@ def check_override(self, override: FunctionLike, original: FunctionLike,
         if isinstance(original, FunctionLike) and isinstance(override, FunctionLike):
             if original_class_or_static and not override_class_or_static:
                 fail = True
+            if isinstance(original, CallableType) and isinstance(override, CallableType):
+                if original.type_guard is not None and override.type_guard is None:
+                    fail = True
 
         if is_private(name):
             fail = False
diff --git a/test-data/unit/check-typeguard.test b/test-data/unit/check-typeguard.test
index e4bf3dd5c931..01a8dfc9e69b 100644
--- a/test-data/unit/check-typeguard.test
+++ b/test-data/unit/check-typeguard.test
@@ -287,10 +287,10 @@ def main(a: object) -> None:
         reveal_type(a)  # N: Revealed type is 'builtins.float'
 [builtins fixtures/tuple.pyi]
 
-[case testTypeGuardMethodOverride-skip]
+[case testTypeGuardMethodOverride]
 from typing_extensions import TypeGuard
 class C:
     def is_float(self, a: object) -> TypeGuard[float]: pass
 class D(C):
-    def is_float(self, a: object) -> bool: pass  # E: Some error
+    def is_float(self, a: object) -> bool: pass  # E: Signature of "is_float" incompatible with supertype "C"
 [builtins fixtures/tuple.pyi]

From d7a911596a52c4d893ed4ce14c6d0ea55eaa8f71 Mon Sep 17 00:00:00 2001
From: Kamil Turek <kamil.turek@hotmail.com>
Date: Thu, 8 Apr 2021 23:15:41 +0200
Subject: [PATCH 2/2] Use elif to avoid redundant check

---
 mypy/checker.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mypy/checker.py b/mypy/checker.py
index 50b503989800..704bf34e2db2 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -1610,7 +1610,7 @@ def check_override(self, override: FunctionLike, original: FunctionLike,
         if isinstance(original, FunctionLike) and isinstance(override, FunctionLike):
             if original_class_or_static and not override_class_or_static:
                 fail = True
-            if isinstance(original, CallableType) and isinstance(override, CallableType):
+            elif isinstance(original, CallableType) and isinstance(override, CallableType):
                 if original.type_guard is not None and override.type_guard is None:
                     fail = True