Weird compiler reporting when `for` is forgotten

[Seldaek]

I don't know if it's fixable, but it would be nice if the ... || {} syntax created an error when it doesn't make sense (or does it and I am confused?)

To reproduce, try to compile:

fn main() {
    let test = [0, 1];
    test.iter().advance |val| {
        println(arg);
    }
}

As you see for is missing at line 3, but the compiler reports:

test.rs:3:25: 3:28 error: unresolved name `val`. Did you mean `test`?
test.rs:3     test.iter().advance |val| {
                                   ^~~
test.rs:4:16: 4:19 error: unresolved name `arg`. Did you mean `test`?
test.rs:4         println(arg);
                          ^~~

Which is very misleading.

[thestinger]

The old for syntax is gone, but the error reporting here could still likely be improved. I don't really understand why that's making it past the parser to resolve.

[huonw]

Triage: still the same message.

It's parsing it as (test.iter().advance) BIT_OR val BIT_OR ({ println(arg); }), since blocks are expressions, and all that.

[alexcrichton]

This bug is quite old at this point, and for loops have progressed quite a bit since that point, so I'm going to close this for now as we definitely shouldn't be recommending for there any more!