Fix TypedDict against PartialTypedDict matching in is_subset_eq

Summary:
* Forbid updating a read-only field. This is in the spec: https://typing.python.org/en/latest/spec/typeddict.html#update-method.
* Do an is_subset_eq check on field types. Mypy and pyright disagree on whether the field types need to be identical or one needs to be a subtype of the other, so I took the more lenient of the two approaches.
* Don't error on extra items, as neither mypy nor pyright does so, presumably because a TypedDict can have extra items through inheritance.

Reviewed By: samwgoldman

Differential Revision: D78768100

fbshipit-source-id: d3c24de975fa2620e9c3174e8e453d5f08e492fe

Author: rchen152

conformance/third_party/conformance.exp

@@ -10225,13 +10225,13 @@
   "typeddicts_readonly_update.py": [
     {
       "code": -2,
-      "column": 13,
+      "column": 10,
       "concise_description": "No matching overload found for function `A.update`",
       "description": "No matching overload found for function `A.update`\n  Possible overloads:\n  (__m: Partial[A], /) -> None [closest match]\n  (__m: Iterable[tuple[Literal['y'], int]], /) -> None\n  (*, y: int) -> None",
-      "line": 34,
+      "line": 23,
       "name": "no-matching-overload",
-      "stop_column": 16,
-      "stop_line": 34
+      "stop_column": 14,
+      "stop_line": 23
     }
   ],
   "typeddicts_required.py": [

conformance/third_party/conformance.result

@@ -480,10 +480,7 @@
     "Line 132: Expected 1 errors"
   ],
   "typeddicts_readonly_kwargs.py": [],
-  "typeddicts_readonly_update.py": [
-    "Line 23: Expected 1 errors",
-    "Line 34: Unexpected errors [\"No matching overload found for function `A.update`\\n  Possible overloads:\\n  (__m: Partial[A], /) -> None [closest match]\\n  (__m: Iterable[tuple[Literal['y'], int]], /) -> None\\n  (*, y: int) -> None\"]"
-  ],
+  "typeddicts_readonly_update.py": [],
   "typeddicts_required.py": [
     "Line 62: Expected 1 errors",
     "Line 74: Unexpected errors [\"Expected a type form, got instance of `Literal['RecursiveMovie']`\"]"

conformance/third_party/results.json

@@ -1,9 +1,9 @@
 {
   "total": 136,
-  "pass": 70,
-  "fail": 66,
-  "pass_rate": 0.51,
-  "differences": 290,
+  "pass": 71,
+  "fail": 65,
+  "pass_rate": 0.52,
+  "differences": 288,
   "passing": [
     "aliases_explicit.py",
     "aliases_newtype.py",
@@ -74,6 +74,7 @@
     "typeddicts_operations.py",
     "typeddicts_readonly.py",
     "typeddicts_readonly_kwargs.py",
+    "typeddicts_readonly_update.py",
     "typeddicts_usage.py"
   ],
   "failing": {
@@ -140,7 +141,6 @@
     "typeddicts_inheritance.py": 1,
     "typeddicts_readonly_consistency.py": 1,
     "typeddicts_readonly_inheritance.py": 4,
-    "typeddicts_readonly_update.py": 2,
     "typeddicts_required.py": 2,
     "typeddicts_type_consistency.py": 1
   },

pyrefly/lib/solver/subset.rs

@@ -737,8 +737,7 @@ impl<'a, Ans: LookupAnswer> Subset<'a, Ans> {
                 };
                 args_subset && self.is_subset_eq(&l.ret, &u.ret)
             }
-            (Type::TypedDict(got), Type::TypedDict(want))
-            | (Type::TypedDict(got), Type::PartialTypedDict(want)) => {
+            (Type::TypedDict(got), Type::TypedDict(want)) => {
                 // For each key in `want`, `got` has the corresponding key
                 // and the corresponding value type in `got` is consistent with the value type in `want`.
                 // For each required key in `got`, the corresponding key is required in `want`.
@@ -763,6 +762,20 @@ impl<'a, Ans: LookupAnswer> Subset<'a, Ans> {
                         .is_none_or(|want_v| got_v.required == want_v.required)
                 })
             }
+            (Type::TypedDict(got), Type::PartialTypedDict(want)) => {
+                let got_fields = self.type_order.typed_dict_fields(got);
+                let want_fields = self.type_order.typed_dict_fields(want);
+                want_fields.iter().all(|(k, want_v)| {
+                    got_fields.get(k).is_some_and(|got_v| {
+                        if want_v.is_read_only() {
+                            // ReadOnly can only be updated with Never (i.e., no update)
+                            self.is_subset_eq(&got_v.ty, &Type::never())
+                        } else {
+                            self.is_subset_eq(&got_v.ty, &want_v.ty)
+                        }
+                    })
+                })
+            }
             (Type::TypedDict(_), Type::SelfType(cls))
                 if cls == self.type_order.stdlib().typed_dict_fallback() =>
             {

pyrefly/lib/test/typed_dict.rs

@@ -123,7 +123,6 @@ def f(c: C | Any):
 );
 
 testcase!(
-    bug = "a1.update(a2) should be an error and a.update(b) should not be",
     test_typed_dict_readonly_partial_update,
     r#"
 from typing import Never, NotRequired, TypedDict, ReadOnly
@@ -135,14 +134,14 @@ class A(TypedDict):
 
 a1: A = {"x": 1, "y": 2}
 a2: A = {"x": 3, "y": 4}
-a1.update(a2) 
+a1.update(a2) # E: No matching overload 
 
 class B(TypedDict):
     x: NotRequired[Never]
     y: ReadOnly[int]
 
 def update_a(a: A, b: B) -> None:
-    a.update(b) # E: No matching overload found for function `A.update` 
+    a.update(b)
     "#,
 );