Fix recursion with NamedTuple and recursive type alias

Fixes #19941

Author: hauntsaninja

mypy/types.py

@@ -3934,6 +3934,14 @@ def strategy(self, items: list[list[mypy.nodes.TypeAlias]]) -> list[mypy.nodes.T
             out.extend(item)
         return out
 
+    def visit_instance(self, t: Instance) -> list[mypy.nodes.TypeAlias]:
+        aliases = super().visit_instance(t)
+        special_alias = t.type.special_alias
+        if special_alias is None or special_alias in self.seen_alias_nodes:
+            return aliases
+        self.seen_alias_nodes.add(special_alias)
+        return aliases + [special_alias] + special_alias.target.accept(self)
+
     def visit_type_alias_type(self, t: TypeAliasType, /) -> list[mypy.nodes.TypeAlias]:
         assert t.alias is not None
         if t.alias not in self.seen_alias_nodes:

test-data/unit/check-namedtuple.test

@@ -1530,3 +1530,20 @@ class Base:
         names = [name for name in namespace if fail]  # E: Name "fail" is not defined
         self.n = namedtuple("n", names)  # E: NamedTuple type as an attribute is not supported
 [builtins fixtures/tuple.pyi]
+
+[case testNamedTupleRecursiveTypeAlias]
+from __future__ import annotations
+from typing import Awaitable, NamedTuple, TypeVar, Union
+
+T = TypeVar("T")
+AwaitOrValue = Union[Awaitable[T], T]
+
+class Leaf(NamedTuple):
+    data: Wrapper
+
+class Wrapper(NamedTuple):
+    result: AwaitOrValue[Leaf]
+
+def foo(value: Leaf | Wrapper) -> None:
+    wrapper: Wrapper = value  # E: Incompatible types in assignment (expression has type "Union[Leaf, Wrapper]", variable has type "Wrapper")
+[builtins fixtures/tuple.pyi]