Rustc compiler panic prints to stdout - breaks RLS comms

[alexheretic]

With this bug I'm less interested in the rustc bugs themselves rather that they can cause output to stdout. Doing so is unacceptable for the Rls as it breaks jsonrpc, and in a way that is not currently recoverable by vscode-jsonrpc library (used by atom & vscode RLS clients).

Is there any way we can minimise the possibility of rustc printing stdout in RLS usage?

Rustc stdout after panic

Usage: rustc [OPTIONS] INPUT
Options:
     -h, --help          Display this message
...etc...

For example, printing the help instead to stderr would be enough to prevent jsonrpc abuse in RLS.

Atom console

[nrc]

This looks like we're printing the --help message after a panic, which is kind of weird. @rust-lang/compiler any idea why that would happen? @alexheretic does that look like what is happening?

[alexheretic]

@nrc that's exactly what it looks like. I'm getting this consistently too, with the stdout each panic now requires an Rls & Rls client restart :(. The panic themselves seem to occur at certain situations when the code won't compile, ie I encounter it eventually by editing code.

[michaelwoerister]

This looks like we're printing the --help message after a panic

Weird indeed :)

@alexheretic, maybe the full stack trace of the panic might help diagnose the problem. Can you provide a screenshot showing the stack frames above 12?

[alexheretic]

The traces themselves seemed very similar to those reported in rust-lang/rls#754. I'll add my trace next time I encounter one.

[nikomatsakis]

(What is a "RI"?)

[oli-obk]

rls 😆 I wondered the same thing when I first saw the title

[alexheretic]

That is something I can clarify easily.

[nikomatsakis]

Can we reproduce this running from the command line?

[nikomatsakis]

Should be plenty of ICEs to pick from in the repo :)