Fix constraint inference of CallableType and TypeType (#2895)

Together with #2894 this fixes #2892.

Author: miedzinski

mypy/constraints.py

@@ -381,6 +381,8 @@ def visit_callable_type(self, template: CallableType) -> List[Constraint]:
             return res
         elif isinstance(self.actual, Overloaded):
             return self.infer_against_overloaded(self.actual, template)
+        elif isinstance(self.actual, TypeType):
+            return infer_constraints(template.ret_type, self.actual.item, self.direction)
         else:
             return []
 
@@ -442,9 +444,9 @@ def visit_overloaded(self, template: Overloaded) -> List[Constraint]:
         return res
 
     def visit_type_type(self, template: TypeType) -> List[Constraint]:
-        if isinstance(self.actual, CallableType) and self.actual.is_type_obj():
+        if isinstance(self.actual, CallableType):
             return infer_constraints(template.item, self.actual.ret_type, self.direction)
-        elif isinstance(self.actual, Overloaded) and self.actual.is_type_obj():
+        elif isinstance(self.actual, Overloaded):
             return infer_constraints(template.item, self.actual.items()[0].ret_type,
                                      self.direction)
         elif isinstance(self.actual, TypeType):

test-data/unit/check-inference.test

@@ -664,6 +664,14 @@ lb = [b]
 l = lb # E: Incompatible types in assignment (expression has type List[bool], variable has type List[A])
 [builtins fixtures/for.pyi]
 
+[case testGenericFunctionWithTypeTypeAsCallable]
+from typing import Callable, Type, TypeVar
+T = TypeVar('T')
+def f(x: Callable[..., T]) -> T: return x()
+class A: pass
+x = None  # type: Type[A]
+y = f(x)
+reveal_type(y)  # E: Revealed type is '__main__.A*'
 
 -- Generic function inference with unions
 -- --------------------------------------