Use the instance type to determine if an object is a promise.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 77ea4c3200104d5cb514af8ce50ca37d838cf076..1503a1d0f386117e76753ab4f0f400cea1881d35 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -3037,12 +3037,7 @@ bool Value::IsSetIterator() const {
   return Utils::OpenHandle(this)->IsJSSetIterator();
 }
 
-
-bool Value::IsPromise() const {
-  auto self = Utils::OpenHandle(this);
-  return i::Object::IsPromise(self);
-}
-
+bool Value::IsPromise() const { return Utils::OpenHandle(this)->IsJSPromise(); }
 
 MaybeLocal<String> Value::ToString(Local<Context> context) const {
   auto obj = Utils::OpenHandle(this);