From b9823f6fe5f4701b36ed464143df6681bfbfb3b4 Mon Sep 17 00:00:00 2001
From: jetsetbrand <rahulj9223@gmail.com>
Date: Fri, 28 Nov 2025 16:05:28 +0530
Subject: [PATCH 1/3] Fix: Treat bare generic TypeAliasType assignment as
 variable (Fixes #20308)

---
 mypy/semanal.py | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/mypy/semanal.py b/mypy/semanal.py
index 8179813c7171..f1260cf15efb 100644
--- a/mypy/semanal.py
+++ b/mypy/semanal.py
@@ -3493,13 +3493,28 @@ def is_type_ref(self, rv: Expression, bare: bool = False) -> bool:
         else:
             valid_refs = type_constructors
 
-        if isinstance(rv.node, TypeAlias) or rv.fullname in valid_refs:
+        if isinstance(rv.node, TypeAlias):
+            # Fix for #20308: Reassignment of a generic TypeAliasType (PEP 695)
+            # should be evaluated as a variable assignment, not a type expression.
+            # This allows usage like `B = A` where `type A[T] = ...` without
+            # triggering "Missing type parameters" error.
+            if (
+                bare
+                and rv.node.python_3_12_type_alias
+                and rv.node.alias_tvars
+            ):
+                return False
             return True
+
+        if rv.fullname in valid_refs:
+            return True
+
         if isinstance(rv.node, TypeInfo):
             if bare:
                 return True
             # Assignment color = Color['RED'] defines a variable, not an alias.
             return not rv.node.is_enum
+
         if isinstance(rv.node, Var):
             return rv.node.fullname in NEVER_NAMES
 

From c1f3b1eefe0eff532a789537185509c5ae76bd81 Mon Sep 17 00:00:00 2001
From: jetsetbrand <rahulj9223@gmail.com>
Date: Sat, 29 Nov 2025 10:44:38 +0530
Subject: [PATCH 2/3] Add regression test with typing-full fixture

---
 test-data/unit/check-python312.test | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/test-data/unit/check-python312.test b/test-data/unit/check-python312.test
index a67ed4abcffa..9ec55d194342 100644
--- a/test-data/unit/check-python312.test
+++ b/test-data/unit/check-python312.test
@@ -2237,3 +2237,14 @@ class D[*Ts](Generic[Unpack[Us]]):  # E: Generic[...] base class is redundant \
                                     # E: Can only use one type var tuple in a class def
     pass
 [builtins fixtures/tuple.pyi]
+
+[case testPep695GenericTypeAliasReassignment]
+from typing import reveal_type
+
+type A[T] = T | str
+B = A
+reveal_type(B)
+[out]
+main:5: note: Revealed type is "typing.TypeAliasType"
+[builtins fixtures/tuple.pyi]
+[typing fixtures/typing-full.pyi]

From 9da85e6573987594795a0cd1e665d0b97b12d438 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Sat, 29 Nov 2025 05:19:05 +0000
Subject: [PATCH 3/3] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 mypy/semanal.py | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/mypy/semanal.py b/mypy/semanal.py
index f1260cf15efb..936d2ba2c9d4 100644
--- a/mypy/semanal.py
+++ b/mypy/semanal.py
@@ -3498,11 +3498,7 @@ def is_type_ref(self, rv: Expression, bare: bool = False) -> bool:
             # should be evaluated as a variable assignment, not a type expression.
             # This allows usage like `B = A` where `type A[T] = ...` without
             # triggering "Missing type parameters" error.
-            if (
-                bare
-                and rv.node.python_3_12_type_alias
-                and rv.node.alias_tvars
-            ):
+            if bare and rv.node.python_3_12_type_alias and rv.node.alias_tvars:
                 return False
             return True