rustc should suggest using .to_owned() for ~str

[limeburst]

rustc gives

error: mismatched types: expected `core::result::Result<int,~str>` but found `core::result::Result<<generic integer #0>,&'static str>` (expected box but found &-ptr)

for

fn example() -> Result<int, ~str> {
    match Some("") {
        Some("") => Ok(0),
        _ => Err("")
    }
}

rustc could suggest using to_owned().

[Ryman]

It's hard to get suggestions like this to be useful. If rustc were to give a suggestion, it would be best to give a list of all fields and methods that would resolve the type error. Although, that would probably be considered spammy.

I'm not in favor of hardcoding this behavior for &str.

[limeburst]

cc @cmr

[huonw]

(FWIW, if this were implemented, it should be suggesting .to_strbuf or (in future) .to_string, since ~str is gone.)

[limeburst]

Sure, anything less cryptic would be better.

[japaric]

FWIW, for this particular example, I would prefer rustc to recommend changing the signature to -> Result<int, &'static str>, since the "to_owned()" allocation is not needed.

[alexcrichton]

~str is no longer a type and I think our bases are pretty well covered here today, so closing