Bug 1665026 - Prevent ToResultInvoke from being instantiated with a raw pointer result type. r=janv

Differential Revision: https://phabricator.services.mozilla.com/D90264

mfbt/ResultExtensions.h

@@ -66,6 +66,14 @@ template <typename R, typename RArgMapper, typename Func, typename... Args>
 Result<R, nsresult> ToResultInvokeInternal(const Func& aFunc,
                                            const RArgMapper& aRArgMapper,
                                            Args&&... aArgs) {
+  // XXX Thereotically, if R is a pointer to a non-refcounted type, this might
+  // be a non-owning pointer, but unless we find a case where this actually is
+  // relevant, it's safe to forbid any raw pointer result.
+  static_assert(
+      !std::is_pointer_v<R>,
+      "Raw pointer results are not supported, please specify a smart pointer "
+      "result type explicitly, so that getter_AddRefs is used");
+
   R res;
   nsresult rv = aFunc(std::forward<Args>(aArgs)..., aRArgMapper(res));
   if (NS_FAILED(rv)) {