Macro features_macro 

macro_rules! features_macro {
    (
        @TARGET: $target:ident;
        @CFG: $cfg:meta;
        @MACRO_NAME: $macro_name:ident;
        @MACRO_ATTRS: $(#[$macro_attrs:meta])*
        $(@BIND_FEATURE_NAME: $bind_feature:tt; $feature_impl:tt;)*
        $(@FEATURE: $feature:ident: $feature_lit:tt: $feature_doc:tt;)*
    ) => { ... };
}

Available on crate feature full only.