Allow @overload on async functions as well (#472)

Author: asottile

pyflakes/checker.py

@@ -72,9 +72,11 @@ def getAlternatives(n):
 if PY35_PLUS:
     FOR_TYPES = (ast.For, ast.AsyncFor)
     LOOP_TYPES = (ast.While, ast.For, ast.AsyncFor)
+    FUNCTION_TYPES = (ast.FunctionDef, ast.AsyncFunctionDef)
 else:
     FOR_TYPES = (ast.For,)
     LOOP_TYPES = (ast.While, ast.For)
+    FUNCTION_TYPES = (ast.FunctionDef,)
 
 # https://github.com/python/typed_ast/blob/1.4.0/ast27/Parser/tokenizer.c#L102-L104
 TYPE_COMMENT_RE = re.compile(r'^#\s*type:\s*')
@@ -642,7 +644,7 @@ def is_typing_overload_decorator(node):
         )
 
     return (
-        isinstance(value.source, ast.FunctionDef) and
+        isinstance(value.source, FUNCTION_TYPES) and
         any(
             is_typing_overload_decorator(dec)
             for dec in value.source.decorator_list

pyflakes/test/test_type_annotations.py

@@ -56,6 +56,24 @@ def f(s):
             return s
         """)
 
+    @skipIf(version_info < (3, 5), 'new in Python 3.5')
+    def test_typingOverloadAsync(self):
+        """Allow intentional redefinitions via @typing.overload (async)"""
+        self.flakes("""
+        from typing import overload
+
+        @overload
+        async def f(s):  # type: (None) -> None
+            pass
+
+        @overload
+        async def f(s):  # type: (int) -> int
+            pass
+
+        async def f(s):
+            return s
+        """)
+
     def test_overload_with_multiple_decorators(self):
         self.flakes("""
             from typing import overload