Fix generic NamedTuple class pattern member lookup

Author: paulorochaoliveira

mypy/checkpattern.py

@@ -665,14 +665,20 @@ def visit_class_pattern(self, o: ClassPattern) -> PatternType:
         #
         # Check keyword patterns
         #
+        narrowed_type_for_members = narrowed_type
+        if isinstance(narrowed_type_for_members, TupleType) and (
+            narrowed_type_for_members.partial_fallback.type.is_named_tuple
+        ):
+            narrowed_type_for_members = 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,
@@ -722,8 +728,6 @@ def get_class_pattern_type_ranges(self, typ: Type, o: ClassPattern) -> list[Type
 
         if isinstance(p_typ, FunctionLike) and p_typ.is_type_obj():
             typ = fill_typevars_with_any(p_typ.type_object())
-            if isinstance(typ, TupleType) and typ.partial_fallback.type.is_named_tuple:
-                typ = typ.partial_fallback
             return [TypeRange(typ, is_upper_bound=False)]
         if (
             isinstance(o.class_ref.node, Var)

test-data/unit/check-python310.test

@@ -962,18 +962,20 @@ match m:
         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
 
-m: A[int]
-
-match m:
-    case A(a=i):
-        reveal_type(i)  # N: Revealed type is "builtins.int"
+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]
 

test-data/unit/check-python312.test

@@ -1677,16 +1677,18 @@ e: M[bool]  # E: Value of type variable "T" of "M" cannot be "bool"
 [typing fixtures/typing-full.pyi]
 
 [case testMatchClassPatternCapturePEP695GenericNamedTupleAlreadyKnown]
+# flags: --warn-unreachable
 from typing import NamedTuple
 
 class N[T](NamedTuple):
     x: T
 
-n: N[int]
-
-match n:
-    case N(x=value):
-        reveal_type(value)  # N: Revealed type is "builtins.int"
+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]