--- a/js/src/vm/SharedMem.h
+++ b/js/src/vm/SharedMem.h
@@ -73,21 +73,22 @@ class SharedMem {
   }
 
   // Reinterpret-cast the pointer to type U, preserving sharedness.
   // Eg, "obj->dataPointerEither().cast<uint8_t*>()" yields a
   // SharedMem<uint8_t*>.
   template <typename U>
   inline SharedMem<U> cast() const {
 #ifdef DEBUG
-    MOZ_ASSERT(asValue() %
-                   sizeof(mozilla::Conditional<
-                          mozilla::IsVoid<std::remove_pointer_t<U>>::value,
-                          char, std::remove_pointer_t<U>>) ==
-               0);
+    MOZ_ASSERT(
+        asValue() %
+            sizeof(
+                mozilla::Conditional<std::is_void_v<std::remove_pointer_t<U>>,
+                                     char, std::remove_pointer_t<U>>) ==
+        0);
     if (sharedness_ == IsUnshared) {
       return SharedMem<U>::unshared(unwrap());
     }
 #endif
     return SharedMem<U>::shared(unwrap());
   }
 
   explicit operator bool() { return ptr_ != nullptr; }
@@ -118,20 +119,22 @@ class SharedMem {
     return result;
   }
 
   uintptr_t asValue() const { return reinterpret_cast<uintptr_t>(ptr_); }
 
   // Cast to char*, add nbytes, and cast back to T.  Simplifies code in a few
   // places.
   SharedMem addBytes(size_t nbytes) {
-    MOZ_ASSERT(nbytes % sizeof(mozilla::Conditional<
-                               mozilla::IsVoid<std::remove_pointer_t<T>>::value,
-                               char, std::remove_pointer_t<T>>) ==
-               0);
+    MOZ_ASSERT(
+        nbytes %
+            sizeof(
+                mozilla::Conditional<std::is_void_v<std::remove_pointer_t<T>>,
+                                     char, std::remove_pointer_t<T>>) ==
+        0);
     return SharedMem(
         reinterpret_cast<T>(reinterpret_cast<char*>(ptr_) + nbytes), *this);
   }
 
   T unwrap() const { return ptr_; }
 
   T unwrapUnshared() const {
     MOZ_ASSERT(sharedness_ == IsUnshared);