Macros can have multiple pattern to match the syntax, so you have to write a seperate pattern for every case seperatly like this:
macro_rules! default(
($t:ident, $($n:ident, $v:expr),*) => {
$t { $($n: $v),*, ..Default::default() }
};
($t:ident, $($n:ident: $v:expr),*) => {
default!($t, $($n, $v),*)
};
)
As you can see there are two patterns, the first matching pairs seperated by comma and the second one pairs seperated by colon.