Macro delegate_providers 

macro_rules! delegate_providers {
    (
        $target:ident {
            $($method:ident -> $return:ty)*
        }
    ) => { ... };
    (
        $target:ident ($state:expr) {
            $($method:ident -> $return:ty)*
        }
    ) => { ... };
}

Available on crate feature formatting only.