Discrepancy in closure modes

[kyledj]

The following code compiles and works as expected:

let a = &"something".all(|c: char| -> bool { c == 'a' });

This code, however:

let char_is_a = fn&(c: char) -> bool { c == 'a' };
let b = &"something".all(char_is_a);

gives the following error:

str_tut.rs:28:26: 28:35 error: mismatched types: expected `fn&(++:char) -> bool` but found `fn&(char) -> bool` (expected argument mode ++, but found +)
str_tut.rs:28   let b = &"something".all(char_is_a);
                                        ^~~~~~~~~
error: aborting due to previous error

If I add the mode to the char_is_a definition, it works. It just seems odd to have this discrepancy.

[nikomatsakis]

What version of rustc are you using? I would not expect this to be true on the most recent incoming, but earlier versions and master may still exhibit this behavior.

[nikomatsakis]

In particular this commit 9284179 most likely fixes this issue.

[kyledj]

I originally had this issue on master. I compiled incoming (73b2a93), and had the same issue, so not sure if it is resolved.

[nikomatsakis]

So more specifically, with the latest incoming, this test works for me:

fn main() {
    fn foo(c: char) -> bool { c == 'a' }
    let a = &"something".all(foo);
}

[nikomatsakis]

As did this:

fn main() {
    let foo = fn&(c: char) -> bool { c == 'a' };
    let a = &"something".all(foo);
}

[kyledj]

Ugh. I'm not sure what was up with my environment when I was running rustc this morning, but recompiling incoming seemed to have fixed it. The latest does fix these issues.