Take extra_items into account when synthesizing get()

Summary:
For #946.

A few asserted types changed because we don't simplify unions containing `object`.

Reviewed By: samwgoldman

Differential Revision: D80870295

fbshipit-source-id: c52e3163f6b16410b8fbc3e2f7d49c3abde6abc7

Author: rchen152

pyrefly/lib/alt/class/typed_dict.rs

@@ -436,7 +436,8 @@ impl<'a, Ans: LookupAnswer> AnswersSolver<'a, Ans> {
                 ));
             }
         }
-        let signatures = Vec1::from_vec_push(
+        let value_ty = self.get_typed_dict_value_type_from_fields(cls, fields);
+        let mut signatures = Vec1::from_vec_push(
             literal_signatures,
             OverloadType::Function(Function {
                 signature: Callable::list(
@@ -447,17 +448,13 @@ impl<'a, Ans: LookupAnswer> AnswersSolver<'a, Ans> {
                             self.stdlib.str().clone().to_type(),
                             Required::Required,
                         ),
-                        Param::PosOnly(
-                            Some(DEFAULT_PARAM.clone()),
-                            object_ty.clone(),
-                            Required::Optional(None),
-                        ),
                     ]),
-                    object_ty.clone(),
+                    Type::optional(value_ty.clone()),
                 ),
                 metadata: metadata.clone(),
             }),
         );
+        signatures.push(self.get_overload_with_default(&metadata, &self_param, None, value_ty));
         ClassSynthesizedField::new(Type::Overload(Overload {
             signatures,
             metadata: Box::new(metadata),

pyrefly/lib/test/typed_dict.rs

@@ -784,8 +784,8 @@ class C(TypedDict):
     y: str
 def f(c: C, k1: str, k2: int):
     assert_type(c.get("x"), int)
-    assert_type(c.get(k1), object)
-    assert_type(c.get(k1, 0), object)
+    assert_type(c.get(k1), object | None)
+    assert_type(c.get(k1, 0), int | object)
     c.get(k2)  # E: No matching overload
     "#,
 );
@@ -1511,7 +1511,7 @@ def f(x: X):
 );
 
 testcase!(
-    test_get_extra_item,
+    test_getitem_extra_items,
     r#"
 from typing import assert_type, TypedDict
 class A(TypedDict, extra_items=bool):
@@ -1681,3 +1681,15 @@ def f(a: A, k: str):
     assert_type(a.setdefault(k, 0), int | str)
     "#,
 );
+
+testcase!(
+    test_get_extra_items,
+    r#"
+from typing import assert_type, TypedDict
+class A(TypedDict, extra_items=int):
+    x: str
+def f(a: A, k: str):
+    assert_type(a.get(k), str | int | None)
+    assert_type(a.get(k, b'hello world'), str | int | bytes)
+    "#,
+);