Type check when upcasting PassOwnPtr/PassOwnArrayPtr to avoid possible function call ambiguousness

Source/wtf/OwnArrayPtr.h

 /*
  *  Copyright (C) 2006, 2010 Apple Inc. All rights reserved.
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Library General Public
  *  License as published by the Free Software Foundation; either
  *  version 2 of the License, or (at your option) any later version.
  *
  *  This library is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 21 matching lines @@
 template<typename T> class PassOwnArrayPtr;
 template<typename T> PassOwnArrayPtr<T> adoptArrayPtr(T*);
 
 template <typename T> class OwnArrayPtr {
 public:
     typedef T* PtrType;
 
     OwnArrayPtr() : m_ptr(0) { }
 
     // See comment in PassOwnArrayPtr.h for why this takes a const reference.
-    template<typename U> OwnArrayPtr(const PassOwnArrayPtr<U>& o);
+    template<typename U> OwnArrayPtr(const PassOwnArrayPtr<U>&, EnsureOwnArrayPtrConvertibleArgDecl);
 
     // This copy constructor is used implicitly by gcc when it generates
     // transients for assigning a PassOwnArrayPtr<T> object to a stack-allocated
     // OwnArrayPtr<T> object. It should never be called explicitly and gcc
     // should optimize away the constructor when generating code.
     OwnArrayPtr(const OwnArrayPtr<T>&);
 
     ~OwnArrayPtr() { deleteOwnedArrayPtr(m_ptr); }
 
     PtrType get() const { return m_ptr; }
@@ skipping 16 matching lines @@
     OwnArrayPtr& operator=(const PassOwnArrayPtr<T>&);
     OwnArrayPtr& operator=(std::nullptr_t) { clear(); return *this; }
     template<typename U> OwnArrayPtr& operator=(const PassOwnArrayPtr<U>&);
 
     void swap(OwnArrayPtr& o) { std::swap(m_ptr, o.m_ptr); }
 
 private:
     PtrType m_ptr;
 };
 
-template<typename T> template<typename U> inline OwnArrayPtr<T>::OwnArrayPtr(const PassOwnArrayPtr<U>& o)
+template<typename T> template<typename U> inline OwnArrayPtr<T>::OwnArrayPtr(const PassOwnArrayPtr<U>& o, EnsureOwnArrayPtrConvertibleArgDefn)
     : m_ptr(o.leakPtr())
 {
 }
 
 template<typename T> inline void OwnArrayPtr<T>::clear()
 {
     PtrType ptr = m_ptr;
     m_ptr = 0;
     deleteOwnedArrayPtr(ptr);
 }
@@ skipping 58 matching lines @@
 template <typename T> inline T* getPtr(const OwnArrayPtr<T>& p)
 {
     return p.get();
 }
 
 } // namespace WTF
 
 using WTF::OwnArrayPtr;
 
 #endif // WTF_OwnArrayPtr_h