Make ObjectId Send + Sync (#500)

CHANGELOG.md

@@ -25,6 +25,10 @@ Unreleased
       which returns a `Result<&'static [ResourceType], StoreObjectConversionError>`
 - Add missing `StoreObject::Reactor` to the `seasonal-season-5` feature.
 
+### Other
+- Change `PhantomData` in `screeps::local::ObjectId` to better model `ObjectId`'s relationship with the wrapped type.
+    - This allows `ObjectId` to be `Send + Sync` regardless of the wrapped type
+
 0.20.1 (2024-01-09)
 ===================
 

src/local/object_id.rs

@@ -60,8 +60,12 @@ pub use raw::*;
 #[serde(transparent, bound = "")]
 pub struct ObjectId<T> {
     raw: RawObjectId,
+
+    // Needed to consider the `T` as "used" even though we mostly use it as a marker. Because of
+    // auto traits, `PhantomData<fn() -> T>` is used instead: this struct doesn't *hold* a `T`, it
+    // *produces* one.
     #[serde(skip)]
-    phantom: PhantomData<T>,
+    phantom: PhantomData<fn() -> T>,
 }
 
 // traits implemented manually so they don't depend on `T` implementing them.