require subtyping instead of equivalence in selftype of properties (#2404)

Fix #2402 and add test.

Author: elazarg

mypy/checkmember.py

@@ -323,7 +323,7 @@ def check_method_type(functype: FunctionLike, itype: Instance, is_classmethod: b
             # we passed to typ.fallback in analyze_member_access. See #1432.
             if isinstance(selfarg, TupleType):
                 selfarg = selfarg.fallback
-            if not subtypes.is_equivalent(selfarg, itype):
+            if not subtypes.is_subtype(selfarg, itype):
                 msg.invalid_method_type(item, context)
         else:
             # Check that cls argument has type 'Any' or valid class type.

test-data/unit/check-selftype.test

@@ -333,3 +333,21 @@ class E:
     def __new__(cls) -> E:
         reveal_type(cls)  # E: Revealed type is 'def () -> __main__.E'
         return cls()
+
+[case testSelfTypeProperty]
+from typing import TypeVar
+
+T = TypeVar('T', bound='A')
+
+class A:
+    @property
+    def member(self: T) -> T:
+        pass
+
+class B(A):
+    pass
+
+reveal_type(A().member)  # E: Revealed type is '__main__.A*'
+reveal_type(B().member)  # E: Revealed type is '__main__.B*'
+
+[builtins fixtures/property.pyi]