Values parsed inside span

[Kile-Asmussen]

It would be really convenient to be able to do something like this:

rule with_span<T>(thing: rule<T>) -> (T, &'input str)
= span:$( val:thing() ) { (val, span) } ;

As it stands I've made this kludge:

rule with_span<T>(thing: rule<T>) -> (T, &'input str)
= span:&( $( thing() ) ) ) val:thing() { (val, span) } ;

Which apparently parses thing() twice.

[Mingun]

Probably it is better to return Spanned<T> from $(), where

struct Spanned<T> {
  pub value: T,
  pub span: Span,
}

[Kile-Asmussen]

@Mingun Sure, but how?

[Mingun]

I mean, that currently rust-peg returns just Span in that case and it should be modified to return Spanned<T> (if I all understand correctly... I've not looked at the code).

[kevinmehall]

Duplicate of #283. There's a potential wokaround there, but I think it might be worth adding syntax for this.