Impl Try for bool

[scottmcm]

Some previous places this has come up:

[Pre-RFC] Elvis/coalesce + ternary operator

Well, speaking of ?, we could spitball using the Try trait for A || B: if let Ok(v) = Try::into_result(A) { Try::from_ok(v), } else { B } This would be consistent with the current bool behaviour given an implementation like this: struct True; struct False; impl Try for bool { type Success = True; type Error = False; fn into_result(self) -> Result<Self::Ok, Self::Error> { if self { Ok(True) } else { Err(False) } } fn from_error(False: Self::Error) -> Self {…

Something for coalescing; aka generalized/improved `or_else`

I think the only operator that would make sense is ||. It’s already lazy, as this one would be, and currently isn’t overloadable so it wouldn’t break anything. (And you can imagine a impl Try for bool where b? short-circuits on false which would be perfectly consistent with this definition, though I suspect we don’t actually want to allow ? on bool.) OTOH, maybe just the macro would be enough. A bunch of the try{} discussions have talked about “what if I just want to return the first success…

Idea: Early returns and irrefutability

I don’t think you have to do any of this trickery. Parse it as let <pat> = (<expr> || <expr>);. Have a transformation that depending on context makes the || expand to { let temp = <lhs>; if temp { temp } else { <rhs> } or let <pat> = match <lhs> { <pat> => <pat>, _ => <rhs>. Or if we’re ok with || only working with Try types rather than with refutable patterns, add impl Try for bool and desugar || to (approx) match <lhs>.as_result() { Ok(t) => typeof::<lhs>::from_ok(t), => <rhs> }. We have a …

And of course there's

boolinator

I'd personally have no complaints with bool: Try.