Fix generic NamedTuple class pattern matching

mypy/checkpattern.py

@@ -665,14 +665,21 @@ def visit_class_pattern(self, o: ClassPattern) -> PatternType:
         #
         # Check keyword patterns
         #
+        narrowed_type_for_members = narrowed_type
+        proper_narrowed_type_for_members = get_proper_type(narrowed_type_for_members)
+        if isinstance(proper_narrowed_type_for_members, TupleType) and (
+            proper_narrowed_type_for_members.partial_fallback.type.is_named_tuple
+        ):
+            narrowed_type_for_members = proper_narrowed_type_for_members.partial_fallback
+
         can_match = True
         for keyword, pattern in keyword_pairs:
             key_type: Type | None = None
             with self.msg.filter_errors() as local_errors:
                 if keyword is not None:
                     key_type = analyze_member_access(
                         keyword,
-                        narrowed_type,
+                        narrowed_type_for_members,
                         pattern,
                         is_lvalue=False,
                         is_super=False,

test-data/unit/check-python310.test

@@ -960,6 +960,24 @@ match m:
         reveal_type(m)  # N: Revealed type is "__main__.A[builtins.int]"
         reveal_type(i)  # N: Revealed type is "builtins.int"
 
+[case testMatchClassPatternCaptureGenericNamedTupleAlreadyKnown]
+# flags: --warn-unreachable
+from typing import Generic, NamedTuple, TypeVar
+
+T = TypeVar("T")
+
+class A(NamedTuple, Generic[T]):
+    a: T
+
+def f(m: A[int]) -> int:
+    match m:
+        case A(a=i):
+            return i
+        case _:
+            return "oops"  # E: Statement is unreachable
+[builtins fixtures/tuple.pyi]
+[typing fixtures/typing-namedtuple.pyi]
+
 [case testMatchClassPatternCaptureFilledGenericTypeAlias]
 from typing import Generic, TypeVar
 

test-data/unit/check-python312.test

@@ -1676,6 +1676,22 @@ e: M[bool]  # E: Value of type variable "T" of "M" cannot be "bool"
 [builtins fixtures/tuple.pyi]
 [typing fixtures/typing-full.pyi]
 
+[case testMatchClassPatternCapturePEP695GenericNamedTupleAlreadyKnown]
+# flags: --warn-unreachable
+from typing import NamedTuple
+
+class N[T](NamedTuple):
+    x: T
+
+def f(n: N[int]) -> int:
+    match n:
+        case N(x=value):
+            return value
+        case _:
+            return "oops"  # E: Statement is unreachable
+[builtins fixtures/tuple.pyi]
+[typing fixtures/typing-full.pyi]
+
 [case testPEP695GenericTypedDict]
 from typing import TypedDict