Bug 1232418 - Allow mozilla::Tuple to support equality comparison; r=…

…Waldo

--HG--
extra : rebase_source : d57231f1c4a4c58715d2d552dd2e02257a73891e

mfbt/Tuple.h

@@ -95,7 +95,12 @@ struct TupleImpl;
  * of an empty tuple).
  */
 template<std::size_t Index>
-struct TupleImpl<Index> {};
+struct TupleImpl<Index> {
+  bool operator==(const TupleImpl<Index>& aOther) const
+  {
+    return true;
+  }
+};
 
 /*
  * One node of the recursive inheritance hierarchy. It stores the element at
@@ -182,6 +187,10 @@ struct TupleImpl<Index, HeadT, TailT...>
     Tail(*this) = Move(Tail(aOther));
     return *this;
   }
+  bool operator==(const TupleImpl& aOther) const
+  {
+    return Head(*this) == Head(aOther) && Tail(*this) == Tail(aOther);
+  }
 private:
   HeadT mHead;  // The element stored at this index in the tuple.
 };
@@ -246,6 +255,10 @@ class Tuple : public detail::TupleImpl<0, Elements...>
     static_cast<Impl&>(*this) = Move(aOther);
     return *this;
   }
+  bool operator==(const Tuple& aOther) const
+  {
+    return static_cast<const Impl&>(*this) == static_cast<const Impl&>(aOther);
+  }
 };
 
 /**