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|
/// A macro for defining #[cfg] if-else statements.
///
/// This is similar to the `if/elif` C preprocessor macro by allowing definition
/// of a cascade of `#[cfg]` cases, emitting the implementation which matches
/// first.
///
/// This allows you to conveniently provide a long list #[cfg]'d blocks of code
/// without having to rewrite each clause multiple times.
macro_rules! cfg_if {
($(
if #[cfg($($meta:meta),*)] { $($it:item)* }
) else * else {
$($it2:item)*
}) => {
__cfg_if_items! {
() ;
$( ( ($($meta),*) ($($it)*) ), )*
( () ($($it2)*) ),
}
}
}
macro_rules! __cfg_if_items {
(($($not:meta,)*) ; ) => {};
(($($not:meta,)*) ; ( ($($m:meta),*) ($($it:item)*) ), $($rest:tt)*) => {
__cfg_if_apply! { cfg(all($($m,)* not(any($($not),*)))), $($it)* }
__cfg_if_items! { ($($not,)* $($m,)*) ; $($rest)* }
}
}
macro_rules! __cfg_if_apply {
($m:meta, $($it:item)*) => {
$(#[$m] $it)*
}
}
macro_rules! s {
($($(#[$attr:meta])* pub struct $i:ident { $($field:tt)* })*) => ($(
__item! {
#[repr(C)]
$(#[$attr])*
pub struct $i { $($field)* }
}
impl ::dox::Copy for $i {}
impl ::dox::Clone for $i {
fn clone(&self) -> $i { *self }
}
)*)
}
macro_rules! f {
($(pub fn $i:ident($($arg:ident: $argty:ty),*) -> $ret:ty {
$($body:stmt);*
})*) => ($(
#[inline]
#[cfg(not(dox))]
pub unsafe extern fn $i($($arg: $argty),*) -> $ret {
$($body);*
}
#[cfg(dox)]
#[allow(dead_code)]
pub unsafe extern fn $i($($arg: $argty),*) -> $ret {
loop {}
}
)*)
}
macro_rules! __item {
($i:item) => ($i)
}
#[cfg(test)]
mod tests {
cfg_if! {
if #[cfg(test)] {
use std::option::Option as Option2;
fn works1() -> Option2<u32> { Some(1) }
} else {
fn works1() -> Option<u32> { None }
}
}
cfg_if! {
if #[cfg(foo)] {
fn works2() -> bool { false }
} else if #[cfg(test)] {
fn works2() -> bool { true }
} else {
fn works2() -> bool { false }
}
}
cfg_if! {
if #[cfg(foo)] {
fn works3() -> bool { false }
} else {
fn works3() -> bool { true }
}
}
#[test]
fn it_works() {
assert!(works1().is_some());
assert!(works2());
assert!(works3());
}
}
|
