From 4974803ae365a66a860d00e6497cdf46faf4864f Mon Sep 17 00:00:00 2001
From: A5rocks <git@helvetica.moe>
Date: Tue, 18 Aug 2026 21:23:44 -0400
Subject: [PATCH] Make it possible to narrow in unreachable code

---
 mypy/checker.py                            |  5 +++--
 test-data/unit/check-unreachable-code.test | 14 ++++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/mypy/checker.py b/mypy/checker.py
index 33ed5387554d..450e35121abb 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -8200,9 +8200,10 @@ def function_type(self, func: FuncBase) -> FunctionLike:
         return typ
 
     def push_type_map(self, type_map: TypeMap, *, from_assignment: bool = True) -> None:
-        if is_unreachable_map(type_map):
+        unreachable_map = is_unreachable_map(type_map)
+        if unreachable_map:
             self.binder.unreachable()
-        else:
+        if not unreachable_map or self.options.check_unreachable:
             for expr, type in type_map.items():
                 self.binder.put(expr, type, from_assignment=from_assignment)
 
diff --git a/test-data/unit/check-unreachable-code.test b/test-data/unit/check-unreachable-code.test
index 330983dab620..6fcaf0a3d063 100644
--- a/test-data/unit/check-unreachable-code.test
+++ b/test-data/unit/check-unreachable-code.test
@@ -1778,3 +1778,17 @@ def f2() -> None:
         reveal_type(5)  # E: Statement is unreachable \
                         # N: Revealed type is "Literal[5]?"
     "something"  # E: Statement is unreachable
+
+[case testUnreachableCodeStillNarrows]
+# flags: --check-unreachable --warn-unreachable
+import enum
+
+class SomeEnum(enum.Enum):
+    DEFAULT = 0
+
+def f(x: SomeEnum) -> None:
+    if x is SomeEnum.DEFAULT:
+        pass
+    else:
+        reveal_type(x)  # N: Revealed type is "Never"
+[builtins fixtures/tuple.pyi]