|  | //===-- None.h - Simple null value for implicit construction ------*- C++ -*-=// | 
|  | // | 
|  | //                     The LLVM Compiler Infrastructure | 
|  | // | 
|  | // This file is distributed under the University of Illinois Open Source | 
|  | // License. See LICENSE.TXT for details. | 
|  | // | 
|  | //===----------------------------------------------------------------------===// | 
|  | // | 
|  | //  This file provides None, an enumerator for use in implicit constructors | 
|  | //  of various (usually templated) types to make such construction more | 
|  | //  terse. | 
|  | // | 
|  | //===----------------------------------------------------------------------===// | 
|  |  | 
|  | #ifndef LLVM_ADT_NONE_H | 
|  | #define LLVM_ADT_NONE_H | 
|  |  | 
|  | namespace llvm { | 
|  | /// \brief A simple null object to allow implicit construction of Optional<T> | 
|  | /// and similar types without having to spell out the specialization's name. | 
|  | enum class NoneType { None }; | 
|  | const NoneType None = None; | 
|  | } | 
|  |  | 
|  | #endif |