--- a/js/src/frontend/EitherParser.h
+++ b/js/src/frontend/EitherParser.h
@@ -9,34 +9,34 @@
  * ParseHandler but unspecified character type.
  */
 
 #ifndef frontend_EitherParser_h
 #define frontend_EitherParser_h
 
 #include "mozilla/Attributes.h"
 #include "mozilla/Tuple.h"
-#include "mozilla/TypeTraits.h"
 #include "mozilla/Utf8.h"
 #include "mozilla/Variant.h"
 
+#include <type_traits>
 #include <utility>
 
 #include "frontend/BCEParserHandle.h"
 #include "frontend/Parser.h"
 #include "frontend/TokenStream.h"
 
 namespace js {
 
 namespace detail {
 
 template <template <class Parser> class GetThis,
           template <class This> class MemberFunction, typename... Args>
 struct InvokeMemberFunction {
-  mozilla::Tuple<typename mozilla::Decay<Args>::Type...> args;
+  mozilla::Tuple<std::decay_t<Args>...> args;
 
   template <class This, size_t... Indices>
   auto matchInternal(This* obj, std::index_sequence<Indices...>) -> decltype(
       ((*obj).*(MemberFunction<This>::get()))(mozilla::Get<Indices>(args)...)) {
     return ((*obj).*
             (MemberFunction<This>::get()))(mozilla::Get<Indices>(args)...);
   }
 

--- a/js/src/threading/Thread.h
+++ b/js/src/threading/Thread.h
@@ -179,17 +179,17 @@ class ThreadTrampoline {
   // downside: rvalue references becomes lvalue references when used with POD
   // types. This becomes dangerous when attempting to pass POD stored on the
   // stack to the new thread; the rvalue reference will implicitly become an
   // lvalue reference to the stack location. Thus, the value may not exist if
   // the parent thread leaves the frame before the read happens in the new
   // thread. To avoid this dangerous and highly non-obvious footgun, the
   // standard requires a "decay" copy of the arguments at the cost of making it
   // impossible to pass references between threads.
-  mozilla::Tuple<typename mozilla::Decay<Args>::Type...> args;
+  mozilla::Tuple<std::decay_t<Args>...> args;
 
   // Protect the thread id during creation.
   Mutex createMutex;
 
   // Thread can access createMutex.
   friend class js::Thread;
 
  public: