From 699fe778b43798cee77e8c3504348576becebfdf Mon Sep 17 00:00:00 2001
From: Moonchild <moonchild@palemoon.org>
Date: Sun, 8 Nov 2020 23:08:26 +0000
Subject: Bug 1328948 - add is(), as() to Cell.

---
 js/src/gc/Heap.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/js/src/gc/Heap.h b/js/src/gc/Heap.h
index 60e7ef729c..2089415326 100644
--- a/js/src/gc/Heap.h
+++ b/js/src/gc/Heap.h
@@ -28,6 +28,7 @@
 #include "js/HeapAPI.h"
 #include "js/RootingAPI.h"
 #include "js/TracingAPI.h"
+#include "js/TraceKind.h"
 
 struct JSRuntime;
 
@@ -272,6 +273,23 @@ struct Cell
 
     static MOZ_ALWAYS_INLINE bool needWriteBarrierPre(JS::Zone* zone);
 
+    template <class T>
+    inline bool is() const {
+        return getTraceKind() == JS::MapTypeToTraceKind<T>::kind;
+    }
+
+    template<class T>
+    inline T* as() {
+        MOZ_ASSERT(is<T>());
+        return static_cast<T*>(this);
+    }
+
+    template <class T>
+    inline const T* as() const {
+        MOZ_ASSERT(is<T>());
+        return static_cast<const T*>(this);
+    }
+
 #ifdef DEBUG
     inline bool isAligned() const;
     void dump(FILE* fp) const;
-- 
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