rustc stack exhaustion with RUST_LOG=rustc

[thomaslee]

Reproducable vs. the incoming branch using the following source file:

https://gist.github.com/thomaslee/5522568#file-foo-rs

Exact invocation:

RUST_LOG=rustc rustc --out-dir . foo.rs

Dies with:

rust: task 12dc140 ran out of stack

Had a bit of trouble getting a copy of the resulting gdb backtrace because of some technical issues with my desktop, but seems to be easily reproducible. I'll try to get that stack trace in the next day or so if nobody beats me to it.

[thomaslee]

May also be worth noting that I encountered this while digging into issue 4202. I don't think they're related, but I'm not familiar enough with the code base to be certain.

[sanxiyn]

Same as #5958?

[Aatch]

@sanxiyn yes, closing.