Macro entries 

macro_rules! entries {
    (
        $( $key:literal => $variant:ident $( { $( $field:ident : $value:expr ),* $(,)? } )? ),* $(,)?
    ) => { ... };
    (@build Flag $({})?) => { ... };
    (@build Text $({})?) => { ... };
    (@build Text { default: $val:expr }) => { ... };
    (@build Int $({})?) => { ... };
    (@build Int { default: $val:expr }) => { ... };
    (@build Count $({})?) => { ... };
    (@build List $({})?) => { ... };
    (@build List { sep: $val:expr }) => { ... };
    (@build Alias { target: $val:expr }) => { ... };
    (@build $unknown:ident $($rest:tt)*) => { ... };
}