Macro punct 

macro_rules! punct {
    () => { ... };
    (value $value:expr) => { ... };
    (pairs $first:expr; $($punctuation:expr => $next:expr),+ $(,)?) => { ... };
    ($value:ty) => { ... };
}

Names or constructs a comma-punctuated sequence.

• punct!(T) names Punctuated<T>.
• punct!() constructs an empty sequence.
• punct!(value first) constructs one value.
• punct!(pairs first; comma => second, ...) constructs a sequence while retaining every supplied typed comma and its span.