Macro uri 

macro_rules! uri {
    ($(  $name:ident  $(  : $t:ty := $l:literal)?   $( = $lb:literal )?  ),* $(,)?) => { ... };
    (@go $name:ident = $l:literal) => { ... };
    (@go $name:ident : $t:ty := $l:literal) => { ... };
}