Fix invalid type causing namedtuple errors in wrong files

Fixes #8511.

This is a workaround of #4987, where UnboundTypes can leak.

mypy/semanal_namedtuple.py

@@ -8,7 +8,8 @@
 from typing_extensions import Final
 
 from mypy.types import (
-    Type, TupleType, AnyType, TypeOfAny, TypeVarDef, CallableType, TypeType, TypeVarType
+    Type, TupleType, AnyType, TypeOfAny, TypeVarDef, CallableType, TypeType, TypeVarType,
+    UnboundType,
 )
 from mypy.semanal_shared import (
     SemanticAnalyzerInterface, set_callable_name, calculate_tuple_fallback, PRIORITY_FALLBACKS
@@ -334,6 +335,9 @@ def parse_namedtuple_fields_with_types(self, nodes: List[Expression], context: C
                 except TypeTranslationError:
                     return self.fail_namedtuple_arg('Invalid field type', type_node)
                 analyzed = self.api.anal_type(type)
+                # Workaround #4987 and avoid introducing a bogus UnboundType
+                if isinstance(analyzed, UnboundType):
+                    analyzed = AnyType(TypeOfAny.from_error)
                 # These should be all known, otherwise we would defer in visit_assignment_stmt().
                 if analyzed is None:
                     return None

test-data/unit/check-namedtuple.test

@@ -948,3 +948,17 @@ class A:
 
 reveal_type(A().b)  # N: Revealed type is 'Any'
 [builtins fixtures/tuple.pyi]
+
+[case testNamedTupleWrongfile]
+from typing import NamedTuple
+from b import Type1
+Type2 = NamedTuple('Type2', [('x', Type1)])
+[file b.py]
+from typing import NamedTuple
+
+def foo():
+    pass
+
+Type1 = NamedTuple('Type1', [('foo', foo)])  # type: ignore
+
+[builtins fixtures/tuple.pyi]