Fix internal error on TypeForm attribute access (fixes #4747)

pyrefly/lib/alt/attr.rs

@@ -2694,9 +2694,11 @@ impl<'ctx, 'answer, Ans: LookupAnswer> AnswersSolver<'ctx, 'answer, Ans> {
             Type::Annotated(_, _) => acc.push(AttributeBase1::ClassInstance(
                 self.stdlib.generic_alias().clone(),
             )),
+            Type::TypeForm(_) => {
+                acc.push(AttributeBase1::ClassInstance(self.stdlib.object().clone()))
+            }
             // TODO: check to see which ones should have class representations
             Type::SpecialForm(_)
-            | Type::TypeForm(_)
             | Type::TypeLevelDslCall(_)
             | Type::Unpack(_)
             | Type::Concatenate(_, _)

pyrefly/lib/test/typeform.rs

@@ -221,3 +221,29 @@ X: TypeForm[int] = int
 x: X = 0  # E: Expected a type form, got instance of `TypeForm[int]`
     "#,
 );
+
+testcase!(
+    test_typeform_attribute_access,
+    r#"
+import typing
+from typing import TypeVar
+from typing_extensions import TypeForm
+
+T = TypeVar("T")
+
+def field_names(tp: TypeForm[T]):
+    if typing.is_typeddict(tp):
+        return tp.__annotations__.keys()
+    return ()
+    "#,
+);
+
+testcase!(
+    test_typeform_attribute_access_unknown,
+    r#"
+from typing_extensions import TypeForm
+
+def f(tp: TypeForm[int]):
+    tp.not_a_real_attribute  # E: Object of class `object` has no attribute `not_a_real_attribute`
+    "#,
+);