do not narrow classdef in issubset check

Summary:
untype_opt and unwrap_class_object_silently both promote ClassDef to ClassType.

This means that the type of `list` gets narrowed to `list[Any]` after the intersection.

This diff removes that behavior if both sides are ClassDefs

closes #1164

Reviewed By: stroxler

Differential Revision: D84313272

fbshipit-source-id: 866ea3930dae7046a31a9b843dea12ff95310e1a

Author: yangdanny97

pyrefly/lib/alt/narrow.rs

@@ -179,7 +179,9 @@ impl<'a, Ans: LookupAnswer> AnswersSolver<'a, Ans> {
     fn narrow_issubclass(&self, left: &Type, right: &Type, range: TextRange) -> Type {
         let mut res = Vec::new();
         for right in self.as_class_info(right.clone()) {
-            if let Some(left) = self.untype_opt(left.clone(), range)
+            if matches!(left, Type::ClassDef(_)) && matches!(right, Type::ClassDef(_)) {
+                res.push(self.intersect(left, &right))
+            } else if let Some(left) = self.untype_opt(left.clone(), range)
                 && let Some(right) = self.unwrap_class_object_silently(&right)
             {
                 res.push(Type::type_form(self.intersect(&left, &right)))
@@ -193,7 +195,9 @@ impl<'a, Ans: LookupAnswer> AnswersSolver<'a, Ans> {
     fn narrow_is_not_subclass(&self, left: &Type, right: &Type, range: TextRange) -> Type {
         let mut res = Vec::new();
         for right in self.as_class_info(right.clone()) {
-            if let Some(left) = self.untype_opt(left.clone(), range)
+            if matches!(left, Type::ClassDef(_)) && matches!(right, Type::ClassDef(_)) {
+                res.push(self.subtract(left, &right))
+            } else if let Some(left) = self.untype_opt(left.clone(), range)
                 && let Some(right) = self.unwrap_class_object_silently(&right)
             {
                 res.push(Type::type_form(self.subtract(&left, &right)))

pyrefly/lib/test/narrow.rs

@@ -1796,3 +1796,11 @@ def test(a: int, b: str, c: bytes):
         assert_type(c, Literal[b""])
     "#,
 );
+
+testcase!(
+    test_do_not_narrow_class_name,
+    r#"
+assert issubclass(list, object)
+x: list[int] = [1]
+    "#,
+);