include/llvm/ADT/None.h

   1 //===-- None.h - Simple null value for implicit construction ------*- C++ -*-=//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 //  This file provides None, an enumerator for use in implicit constructors
  10 //  of various (usually templated) types to make such construction more
  11 //  terse.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #ifndef LLVM_ADT_NONE_H
  16 #define LLVM_ADT_NONE_H
  17
  18 namespace llvm {
  19 /// A simple null object to allow implicit construction of Optional<T>
  20 /// and similar types without having to spell out the specialization's name.
  21 // (constant value 1 in an attempt to workaround MSVC build issue... )
  22 enum class NoneType { None = 1 };
  23 const NoneType None = NoneType::None;
  24 }
  25
  26 #endif