crash at `>>`

[nrc]

#[derive(Copy, Clone)]
pub struct StdCounter<T: Zero + Add<T, Output = T> + Sub<T, Output = T>> {
    pub value: T
}

error is

thread '<main>' panicked at 'called `Result::unwrap()` on an `Err` value: IllFormedSpan(Span { lo: BytePos(190), hi: BytePos(189), expn_id: ExpnId(4294967295) })', ../src/libcore/result.rs:734

Pretty sure this is due to a libsyntax error (rust-lang/rust#28158), but in case it isn't lets track it here too.

[ben0x539]

I get the a similar IllFormedSpan error on this snippet, which compiles fine with rustc itself. Does that mean it's not a libsyntax error?

fn main() {
    match () {_ => () }
}

Similarly inserting a space between the { and the _ fixes it.

[nrc]

@ben0x539 No, we use more spans than rustc and (more importantly) use them in more interesting ways.

[nrc]

And another example (from liballoc):

fn homura<T: Deref<Target=i32>>(_: T) { }

[nrc]

Should be fixed by rust-lang/rust#28291