add test comments

hauntsaninja · hauntsaninja · commit 2bc9c93b54b4 · 2026-02-02T20:28:19.000-08:00
diff --git a/test-data/unit/check-narrowing.test b/test-data/unit/check-narrowing.test
@@ -3246,14 +3246,15 @@ class B: ...
 
 T = TypeVar("T")
 
-def forgets_about_subclasses1(self, obj: T) -> T:
+def forgets_about_subclasses(self, obj: T) -> T:
     if isinstance(obj, A):
         return A()  # E: Incompatible return value type (got "A", expected "T")
     elif isinstance(obj, B):
         return B()  # E: Incompatible return value type (got "B", expected "T")
     raise
 
 def correct1(self, obj: T) -> T:
+    # TODO: mypy should not error in this case
     if type(obj) == A:
         return A()  # E: Incompatible return value type (got "A", expected "T")
     elif type(obj) == B:
@@ -3262,7 +3263,10 @@ def correct1(self, obj: T) -> T:
 
 T_value = TypeVar("T_value", A, B)
 
-def forgets_about_subclasses2(self, obj: T_value) -> T_value:
+def forgets_about_multiple_inheritance(self, obj: T_value) -> T_value:
+    # Note that it is a little confusing that mypy only errors in the first branch here, but this
+    # is a branch that would be taken by a subclass of both A and B.
+    # See also https://github.com/python/mypy/issues/10302#issuecomment-3832182574
     if isinstance(obj, A):
         return A()  # E: Incompatible return value type (got "A", expected "B")
     elif isinstance(obj, B):
@@ -3485,6 +3489,7 @@ from typing import TypeVar, Any, Type
 
 TargetType = TypeVar("TargetType", int, float, str)
 
+# TODO: this behaviour is incorrect, it will be fixed by improving reachability
 def convert_type(target_type: Type[TargetType]) -> TargetType:
     if target_type == str:
         return str()  # E: Incompatible return value type (got "str", expected "int") \
@@ -3503,6 +3508,7 @@ def convert_type(target_type: Type[TargetType]) -> TargetType:
 from __future__ import annotations
 from typing import Literal
 
+# TODO: the behaviour on some of these test cases is incorrect
 def f1(number: float, i: int):
     if number == i:
         reveal_type(number)  # N: Revealed type is "builtins.float"
