Bug 1300476 - Prevent passing references through InvokeAsync - r=froydnj

Passing references to an async call is dangerous because referenced objects
could be destroyed before/during the call, or even be stored by the callee.

The assertion message points at bug 1313497, which is a follow-up to
(eventually) re-allow references in a safer manner.

MozReview-Commit-ID: FTgI5CGCVAe

--HG--
extra : rebase_source : 3062a7441e21617f559accf4476cdafa5575e8ed

xpcom/threads/MozPromise.h

@@ -14,6 +14,7 @@
 #include "mozilla/Mutex.h"
 #include "mozilla/Monitor.h"
 #include "mozilla/Tuple.h"
+#include "mozilla/TypeTraits.h"
 
 #include "nsTArray.h"
 #include "nsThreadUtils.h"
@@ -968,6 +969,23 @@ private:
   nsAutoPtr<MethodCall<PromiseType, ThisType, ArgTypes...>> mMethodCall;
 };
 
+constexpr bool Any()
+{
+  return false;
+}
+
+template <typename T1>
+constexpr bool Any(T1 a)
+{
+  return static_cast<bool>(a);
+}
+
+template <typename T1, typename... Ts>
+constexpr bool Any(T1 a, Ts... aOthers)
+{
+  return a || Any(aOthers...);
+}
+
 } // namespace detail
 
 template<typename PromiseType, typename ThisType, typename ...ArgTypes, typename ...ActualArgTypes>
@@ -975,6 +993,8 @@ static RefPtr<PromiseType>
 InvokeAsync(AbstractThread* aTarget, ThisType* aThisVal, const char* aCallerName,
             RefPtr<PromiseType>(ThisType::*aMethod)(ArgTypes...), ActualArgTypes&&... aArgs)
 {
+  static_assert(!detail::Any(IsReference<ArgTypes>::value...),
+                "Cannot pass reference types through InvokeAsync, see bug 1313497 if you require it");
   typedef detail::MethodCall<PromiseType, ThisType, ArgTypes...> MethodCallType;
   typedef detail::ProxyRunnable<PromiseType, ThisType, ArgTypes...> ProxyRunnableType;