Keep Any when restricting Union in isinstance (#2446)

ilevkivskyi · JukkaL · commit a488641a0b6c · 2016-11-15T18:35:28.000Z
diff --git a/mypy/subtypes.py b/mypy/subtypes.py
@@ -345,7 +345,8 @@ def restrict_subtype_away(t: Type, s: Type) -> Type:
     Currently just remove elements of a union type.
     """
     if isinstance(t, UnionType):
-        new_items = [item for item in t.items if not is_subtype(item, s)]
+        new_items = [item for item in t.items if (not is_subtype(item, s)
+                                                  or isinstance(item, AnyType))]
         return UnionType.make_union(new_items)
     else:
         return t
diff --git a/test-data/unit/check-unions.test b/test-data/unit/check-unions.test
@@ -35,6 +35,17 @@ def f(x: Union[int, str]) -> None:
 [out]
 main: note: In function "f":
 
+[case testUnionAnyIsInstance]
+from typing import Any, Union
+
+def func(v:Union[int, Any]) -> None:
+    if isinstance(v, int):
+        reveal_type(v) # E: Revealed type is 'builtins.int'
+    else:
+        reveal_type(v) # E: Revealed type is 'Any'
+[builtins fixtures/isinstance.pyi]
+[out]
+main: note: In function "func":
 
 [case testUnionAttributeAccess]
 from typing import Union
