quote_expr!() can cause early abort

[lilyball]

It seems as though using quote_expr!() in a syntax extension after a span_err() will cause rustc to abort early instead of finishing the macro expansion phase.

I hit this in my bytes!() PR, where I ended up having to track whether I had an error and use DummyResult instead of quote_expr!().

[tamird]

@kballard could you include a small reproduction snippet to help make this issue more concrete?

[lilyball]

@tamird I filed this issue almost a year ago. I don't recall the circumstances surrounding it, beyond what I put in the ticket. From re-reading this, I'm pretty sure that what I was saying is that if a syntax extension uses quote_expr!() after having previously invoked cx.span_err() it aborts immediately, instead of continuing the macro expansion phase (span_err() usually doesn't abort the compilation until the end of the macro expansion phase; I think quote_expr!() is basically recursively invoking the macro expansion phase and therefore aborting after the recursive invocation ends).

[steveklabnik]

Triage: this ticket hasn't had an update in almost two years, and there's no reproduction. As such, I'm going to give it a close. If someone runs into this today and can reproduce, please let me know!