Fix typing.overload check to only check imported names

pyflakes/checker.py

@@ -529,6 +529,7 @@ def is_typing_overload_decorator(node):
             (
                 isinstance(node, ast.Name) and
                 node.id in scope and
+                isinstance(scope[node.id], ImportationFrom) and
                 scope[node.id].fullName == 'typing.overload'
             ) or (
                 isinstance(node, ast.Attribute) and

pyflakes/test/test_type_annotations.py

@@ -39,6 +39,28 @@ def g(s):
             return s
         """)
 
+    def test_not_a_typing_overload(self):
+        """regression test for @typing.overload detection bug in 2.1.0"""
+        self.flakes("""
+            x = lambda f: f
+
+            @x
+            def t():
+                pass
+
+            y = lambda f: f
+
+            @x
+            @y
+            def t():
+                pass
+
+            @x
+            @y
+            def t():
+                pass
+        """, m.RedefinedWhileUnused, m.RedefinedWhileUnused)
+
     @skipIf(version_info < (3, 6), 'new in Python 3.6')
     def test_variable_annotations(self):
         self.flakes('''