add missing dcheck to ToLocalChecked

include/v8.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /** \mainpage V8 API Reference Guide
  *
  * V8 is Google's open source JavaScript engine.
  *
  * This set of documents provides reference material generated from the
  * V8 header file, include/v8.h.
@@ skipping 411 matching lines @@
   }
 
   V8_INLINE bool IsEmpty() const { return val_ == nullptr; }
 
   template <class S>
   V8_WARN_UNUSED_RESULT V8_INLINE bool ToLocal(Local<S>* out) const {
     out->val_ = IsEmpty() ? nullptr : this->val_;
     return !IsEmpty();
   }
 
-  V8_INLINE Local<T> ToLocalChecked() {
-    // TODO(dcarney): add DCHECK.
-    return Local<T>(val_);
-  }
+  V8_INLINE Local<T> ToLocalChecked();
 
   template <class S>
   V8_INLINE Local<S> FromMaybe(Local<S> default_value) const {
     return IsEmpty() ? default_value : Local<S>(val_);
   }
 
  private:
   T* val_;
 };
 
@@ skipping 5440 matching lines @@
                        // Must be 1 or -1.
                        int internal_field_index2,
                        WeakCallbackInfo<void>::Callback weak_callback);
   static void* ClearWeak(internal::Object** global_handle);
   static void Eternalize(Isolate* isolate,
                          Value* handle,
                          int* index);
   static Local<Value> GetEternal(Isolate* isolate, int index);
 
   static void CheckIsJust(bool is_just);
+  static void ToLocalEmpty();
 
   template <class T> friend class Handle;
   template <class T> friend class Local;
   template <class T>
+  friend class MaybeLocal;
+  template <class T>
   friend class Maybe;
   template <class T> friend class Eternal;
   template <class T> friend class PersistentBase;
   template <class T, class M> friend class Persistent;
   friend class Context;
 };
 
 
 /**
  * A simple Maybe type, representing an object which may or may not have a
@@ skipping 809 matching lines @@
 }
 
 
 template<class T>
 Local<T> Eternal<T>::Get(Isolate* isolate) {
   return Local<T>(reinterpret_cast<T*>(*V8::GetEternal(isolate, index_)));
 }
 
 
 template <class T>
+Local<T> MaybeLocal<T>::ToLocalChecked() {
+#ifdef V8_ENABLE_CHECKS
+  if (val_ == nullptr) V8::ToLocalEmpty();
+#endif
+  return Local<T>(val_);
+}
+
+
+template <class T>
 T* PersistentBase<T>::New(Isolate* isolate, T* that) {
   if (that == NULL) return NULL;
   internal::Object** p = reinterpret_cast<internal::Object**>(that);
   return reinterpret_cast<T*>(
       V8::GlobalizeReference(reinterpret_cast<internal::Isolate*>(isolate),
                              p));
 }
 
 
 template <class T, class M>
@@ skipping 1129 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_