bugfix for join_simple

Author: ecprice

mypy/join.py

@@ -40,10 +40,10 @@ def join_simple(declaration: Type, s: Type, t: Type, basic: BasicTypes) -> Type:
         # is a good idea.
         return declaration
 
-    if is_subtype(value, declaration):
-        return declaration
+    if declaration is None or is_subtype(value, declaration):
+        return value
 
-    return value
+    return declaration
 
 
 

mypy/test/data/check-isinstance.test

@@ -1,3 +1,19 @@
+[case testJoinAny]
+from typing import List, Any
+
+x = None # type: List[Any]
+
+def foo() -> List[int]: pass
+def bar() -> List[str]: pass
+
+if 1:
+    x = foo()
+else:
+    x = bar()
+
+x * 2
+[builtins fixtures/list.py]
+
 [case testGeneratorExpressionTypes]
 
 class A: y = 1