Use references for &[T]s token type

[yyy33]

Let users decide if they want to clone or not when they use it

where an &T is returned instead of a T:
code

[epage]

Are you meaning to change type Token = T; to type Token = &T;?

If we did then that would first be a breaking change and require waiting until we feel its appropriate to make one.

Also, that signature I gave is incomplete. We'd need that to be type Token<'t> = &'t T. I've not dealt much with GATs, I'm unsure if we can do type Token<'static> = char in other cases. &str streams with a token of char is an example of where we can't use a reference.

It'd be good to experiment with this to see how feasible it is to do something like this before we get to 0.7

[yyy33]

Are you meaning to change type Token = T; to type Token = &T;?

yes

[epage]

Also started #591 to discuss this and other needs.