From 19444614fe34e75ae1b2a596524dd87d8ecd05af Mon Sep 17 00:00:00 2001
From: KotlinIsland <65446343+kotlinisland@users.noreply.github.com>
Date: Tue, 19 Nov 2024 17:07:56 +1000
Subject: [PATCH] remove stupid error about erased self

---
 mypy/checker.py                      | 13 +++++++++----
 test-data/unit/check-based-misc.test | 10 ++++++++++
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/mypy/checker.py b/mypy/checker.py
index 6ccbf5b4e..1e2d4a0e2 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -1497,10 +1497,15 @@ def check_func_def(
                                     # the consistency check will be performed at call sites.
                                     msg = None
                                 elif typ.arg_names[i] in {"self", "cls"}:
-                                    msg = message_registry.ERASED_SELF_TYPE_NOT_SUPERTYPE.format(
-                                        erased.str_with_options(self.options),
-                                        ref_type.str_with_options(self.options),
-                                    )
+                                    if mypy.options._based:
+                                        msg = None
+                                    else:
+                                        msg = (
+                                            message_registry.ERASED_SELF_TYPE_NOT_SUPERTYPE.format(
+                                                erased.str_with_options(self.options),
+                                                ref_type.str_with_options(self.options),
+                                            )
+                                        )
                                 else:
                                     msg = message_registry.MISSING_OR_INVALID_SELF_TYPE
                                 if msg:
diff --git a/test-data/unit/check-based-misc.test b/test-data/unit/check-based-misc.test
index 1be0f1451..cc2ddf655 100644
--- a/test-data/unit/check-based-misc.test
+++ b/test-data/unit/check-based-misc.test
@@ -235,3 +235,13 @@ class B(A):
 \[[tool.mypy.overrides]]
 module="other"
 work_not_properly_function_names=true
+
+
+[case testErasedSelfType]
+
+class A:
+    def f(self: B):
+        reveal_type(self) # N: Revealed type is "__main__.B"
+class B(A): ...
+A().f()  # E: Invalid self argument "A" to attribute function "f" with type "def (self: B) -> None"  [misc]
+B().f()  # no error