Macro punc 

macro_rules! punc {
    (
        pairs $first:expr;
        $punctuation:expr => $second:expr
        $(, $rest_punctuation:expr => $rest_value:expr)*
        $(,)?
    ) => { ... };
    ($value:ty) => { ... };
}

Names or constructs a comma-punctuated sequence.

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