Auto merge of #8097 - wenderen:8090-partialeq-for-mutheap, r=nox

implement PartialEq for MutHeap<JS<T>> and MutNullableHeap<JS<T>>

for #8090

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components/script/dom/bindings/js.rs

@@ -273,6 +273,22 @@ impl<T: HeapGCValue> HeapSizeOf for MutHeap<T> {
     }
 }
 
+impl<T: Reflectable> PartialEq for MutHeap<JS<T>> {
+   fn eq(&self, other: &Self) -> bool {
+        unsafe {
+            *self.val.get() == *other.val.get()
+        }
+    }
+}
+
+impl<T: Reflectable + PartialEq> PartialEq<T> for MutHeap<JS<T>> {
+    fn eq(&self, other: &T) -> bool {
+        unsafe {
+            **self.val.get() == *other
+        }
+    }
+}
+
 /// A holder that provides interior mutability for GC-managed values such as
 /// `JS<T>`, with nullability represented by an enclosing Option wrapper.
 /// Essentially a `Cell<Option<JS<T>>>`, but safer.
@@ -334,6 +350,23 @@ impl<T: Reflectable> MutNullableHeap<JS<T>> {
             *self.ptr.get() = val.map(|p| JS::from_ref(p));
         }
     }
+
+}
+
+impl<T: Reflectable> PartialEq for MutNullableHeap<JS<T>> {
+    fn eq(&self, other: &Self) -> bool {
+        unsafe {
+            *self.ptr.get() == *other.ptr.get()
+        }
+    }
+}
+
+impl<'a, T: Reflectable> PartialEq<Option<&'a T>> for MutNullableHeap<JS<T>> {
+    fn eq(&self, other: &Option<&T>) -> bool {
+        unsafe {
+            *self.ptr.get() == other.map(JS::from_ref)
+        }
+    }
 }
 
 impl<T: HeapGCValue> Default for MutNullableHeap<T> {