pub macro cfg_match {
(
$(cfg($initial_meta:meta) => { $($initial_tokens:tt)* })+
_ => { $($extra_tokens:tt)* }
) => { ... },
(
$(cfg($extra_meta:meta) => { $($extra_tokens:tt)* })*
) => { ... },
(@__items ($($_:meta,)*);) => { ... },
(
@__items ($($no:meta,)*);
(($($yes:meta)?) ($($tokens:tt)*)),
$($rest:tt,)*
) => { ... },
(@__identity $($tokens:tt)*) => { ... },
}🔬This is a nightly-only experimental API. (
cfg_match #115585)Expand description
A macro for defining #[cfg] match-like statements.
It 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.
Trailing _ wildcard match arms are optional and they indicate a fallback branch when
all previous declarations do not evaluate to true.