Alex Crichton | 5d6cf05 | 2015-09-11 14:52:34 -0700 | [diff] [blame] | 1 | /// A macro for defining #[cfg] if-else statements. |
| 2 | /// |
| 3 | /// This is similar to the `if/elif` C preprocessor macro by allowing definition |
| 4 | /// of a cascade of `#[cfg]` cases, emitting the implementation which matches |
| 5 | /// first. |
| 6 | /// |
| 7 | /// This allows you to conveniently provide a long list #[cfg]'d blocks of code |
| 8 | /// without having to rewrite each clause multiple times. |
Alex Crichton | 3150484 | 2015-09-10 23:43:41 -0700 | [diff] [blame] | 9 | macro_rules! cfg_if { |
| 10 | ($( |
| 11 | if #[cfg($($meta:meta),*)] { $($it:item)* } |
| 12 | ) else * else { |
| 13 | $($it2:item)* |
| 14 | }) => { |
| 15 | __cfg_if_items! { |
| 16 | () ; |
| 17 | $( ( ($($meta),*) ($($it)*) ), )* |
| 18 | ( () ($($it2)*) ), |
| 19 | } |
| 20 | } |
| 21 | } |
| 22 | |
Alex Crichton | 3150484 | 2015-09-10 23:43:41 -0700 | [diff] [blame] | 23 | macro_rules! __cfg_if_items { |
| 24 | (($($not:meta,)*) ; ) => {}; |
| 25 | (($($not:meta,)*) ; ( ($($m:meta),*) ($($it:item)*) ), $($rest:tt)*) => { |
| 26 | __cfg_if_apply! { cfg(all($($m,)* not(any($($not),*)))), $($it)* } |
| 27 | __cfg_if_items! { ($($not,)* $($m,)*) ; $($rest)* } |
| 28 | } |
| 29 | } |
| 30 | |
Alex Crichton | 3150484 | 2015-09-10 23:43:41 -0700 | [diff] [blame] | 31 | macro_rules! __cfg_if_apply { |
| 32 | ($m:meta, $($it:item)*) => { |
| 33 | $(#[$m] $it)* |
| 34 | } |
| 35 | } |
| 36 | |
Alex Crichton | 5d6cf05 | 2015-09-11 14:52:34 -0700 | [diff] [blame] | 37 | macro_rules! s { |
| 38 | ($(pub struct $i:ident { $($field:tt)* })*) => ($( |
| 39 | __item! { |
| 40 | #[repr(C)] |
| 41 | pub struct $i { $($field)* } |
| 42 | } |
Alex Crichton | 24abc4f | 2015-09-16 23:54:56 -0700 | [diff] [blame^] | 43 | impl ::dox::Copy for $i {} |
| 44 | impl ::dox::Clone for $i { |
Alex Crichton | 5d6cf05 | 2015-09-11 14:52:34 -0700 | [diff] [blame] | 45 | fn clone(&self) -> $i { *self } |
| 46 | } |
| 47 | )*) |
| 48 | } |
| 49 | |
| 50 | macro_rules! __item { |
| 51 | ($i:item) => ($i) |
| 52 | } |
| 53 | |
Alex Crichton | 3150484 | 2015-09-10 23:43:41 -0700 | [diff] [blame] | 54 | #[cfg(test)] |
| 55 | mod tests { |
| 56 | cfg_if! { |
| 57 | if #[cfg(test)] { |
| 58 | use std::option::Option as Option2; |
| 59 | fn works1() -> Option2<u32> { Some(1) } |
| 60 | } else { |
| 61 | fn works1() -> Option<u32> { None } |
| 62 | } |
| 63 | } |
| 64 | |
| 65 | cfg_if! { |
| 66 | if #[cfg(foo)] { |
| 67 | fn works2() -> bool { false } |
| 68 | } else if #[cfg(test)] { |
| 69 | fn works2() -> bool { true } |
| 70 | } else { |
| 71 | fn works2() -> bool { false } |
| 72 | } |
| 73 | } |
| 74 | |
| 75 | cfg_if! { |
| 76 | if #[cfg(foo)] { |
| 77 | fn works3() -> bool { false } |
| 78 | } else { |
| 79 | fn works3() -> bool { true } |
| 80 | } |
| 81 | } |
| 82 | |
| 83 | #[test] |
| 84 | fn it_works() { |
| 85 | assert!(works1().is_some()); |
| 86 | assert!(works2()); |
| 87 | assert!(works3()); |
| 88 | } |
| 89 | } |