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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(not(any($($not),*)), $($m,)*)), $($it)* }
__cfg_if_items! { ($($not,)* $($m,)*) ; $($rest)* }
}
}
macro_rules! __cfg_if_apply {
($m:meta, $($it:item)*) => {
$(#[$m] $it)*
}
}
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