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// This file is part of ICU4X. For terms of use, please see the file
// called LICENSE at the top level of the ICU4X source tree
/// Make a forking data provider with an arbitrary number of inner providers
/// that are known at build time.
///
/// # Examples
///
/// ```
/// use icu_provider_adapters::fork::ForkByKeyProvider;
///
/// // Some empty example providers:
/// #[derive(PartialEq, Debug)]
/// struct Provider1;
/// #[derive(PartialEq, Debug)]
/// struct Provider2;
/// #[derive(PartialEq, Debug)]
/// struct Provider3;
///
/// // Combine them into one:
/// let forking1 = icu_provider_adapters::make_forking_provider!(
/// ForkByKeyProvider::new,
/// [Provider1, Provider2, Provider3,]
/// );
///
/// // This is equivalent to:
/// let forking2 = ForkByKeyProvider::new(
/// Provider1,
/// ForkByKeyProvider::new(Provider2, Provider3),
/// );
///
/// assert_eq!(forking1, forking2);
/// ```
#[macro_export]
macro_rules! make_forking_provider {
// Base case:
($combo_p:path, [ $a:expr, $b:expr, ]) => {
$combo_p($a, $b)
};
// General list:
($combo_p:path, [ $a:expr, $b:expr, $($c:expr),+, ]) => {
$combo_p($a, $crate::make_forking_provider!($combo_p, [ $b, $($c),+, ]))
};
}
#[cfg(test)]
mod test {
struct Provider1;
struct Provider2;
struct Provider3;
#[test]
fn test_make_forking_provider() {
make_forking_provider!(
crate::fork::ForkByKeyProvider::new,
[Provider1, Provider2, Provider3,]
);
}
}