src/test/run-pass/macro-pat-neg-lit.rs

   1 // Copyright 2017 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 macro_rules! enum_number {
  12     ($name:ident { $($variant:ident = $value:expr, )* }) => {
  13         enum $name {
  14             $($variant = $value,)*
  15         }
  16
  17         fn foo(value: i32) -> Option<$name> {
  18             match value {
  19                 $( $value => Some($name::$variant), )*
  20                 _ => None
  21             }
  22         }
  23     }
  24 }
  25
  26 enum_number!(Change {
  27     Down = -1,
  28     None = 0,
  29     Up = 1,
  30 });
  31
  32 fn main() {
  33     if let Some(Change::Down) = foo(-1) {} else { panic!() }
  34 }
  35