How to match and return a one char?

[Mingun]

I'm tries to write parser, that will return one matched char and I do not see, how I can achieve that in simple way:

rule quotedChar() -> char = ['a'|'b'|'t'|'n'|'v'|'f'|'r'|'e'|'\''|'"'|'\\'];
rule quotedChar() -> char = ch:['a'|'b'|'t'|'n'|'v'|'f'|'r'|'e'|'\''|'"'|'\\'] { ch };

Both infers return type as (). For now I found only such solution:

rule quotedChar() -> char = ch:$['a'|'b'|'t'|'n'|'v'|'f'|'r'|'e'|'\''|'"'|'\\'] { ch.chars().next().unwrap() };

Is there any better solution?

[kevinmehall]

I think that's the best that exists right now. I don't remember the reason why [] doesn't return a reference to the matched item from the input. I'll leave this open to see if that can be added or document the reason why not.

[kevinmehall]

This requires generic associated types to do the right way for parsers over [T] -- ParseElem::Elem should be a reference to avoid having to clone the element to both use it in the pattern and return it. This would also be a breaking change, so deferring until at least 0.7.

[wlott]

ch.chars().next().unwrap()

Is there any better solution?

I personally have found:

char::from_str(s).unwrap()

to read slightly better. Granted, it will panic if the matched string isn't one character while the .chars().unwrap() will only panic if there are zero characters in the string. That may be a good thing or a bad thing depending on your views towards fault tolerance vs rigorous consistency checking.