Make handle ctors explicit

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 310 matching lines @@
   friend Local<Primitive> Undefined(Isolate* isolate);
   friend Local<Primitive> Null(Isolate* isolate);
   friend Local<Boolean> True(Isolate* isolate);
   friend Local<Boolean> False(Isolate* isolate);
   friend class HandleScope;
   friend class EscapableHandleScope;
   template <class F1, class F2, class F3>
   friend class PersistentValueMapBase;
   template<class F1, class F2> friend class PersistentValueVector;
 
-  template <class S>
-  V8_INLINE Local(S* that)
-      : val_(that) {}
+  explicit V8_INLINE Local(T* that) : val_(that) {}
   V8_INLINE static Local<T> New(Isolate* isolate, T* that);
   T* val_;
 };
 
 
 #if !defined(V8_IMMINENT_DEPRECATION_WARNINGS)
 // Local is an alias for Local for historical reasons.
 template <class T>
 using Handle = Local<T>;
 #endif
@@ skipping 435 matching lines @@
     return Persistent<S>::Cast(*this);
   }
 
  private:
   friend class Isolate;
   friend class Utils;
   template<class F> friend class Local;
   template<class F1, class F2> friend class Persistent;
   template<class F> friend class ReturnValue;
 
-  template <class S> V8_INLINE Persistent(S* that) : PersistentBase<T>(that) { }
+  explicit V8_INLINE Persistent(T* that) : PersistentBase<T>(that) {}
   V8_INLINE T* operator*() const { return this->val_; }
   template<class S, class M2>
   V8_INLINE void Copy(const Persistent<S, M2>& that);
 };
 
 
 /**
  * A PersistentBase which has move semantics.
  *
  * Note: Persistent class hierarchy is subject to future changes.
@@ skipping 7665 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // INCLUDE_V8_H_