Don't spin expanding stmt macros.

[goffrie]

If we can't make progress when parsing a macro expansion as a statement then we should just bail.

This alleviates the symptoms shown in e.g. #37113 and #37234 but it doesn't fix the problem that parsing invalid enum bodies (and others) leaves the parser in a crappy state.

I'm not sold on this strategy (checking tokens_consumed), so if anyone has a better idea, I'm all ears!

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[nrc]

I agree that checking consumed tokens does not seem ideal, but I don't have a better idea off the top of my head. cc @jseyfried and @eddyb - any ideas here?

[jseyfried]

I believe we could just change this line to

whileself.token != token::Eof && self.token != token::CloseDelim(token::Brace){

instead of checking token_consumed for progress.

[alexcrichton]

This seems like it may have accidentally stalled out, @nrc is this perhaps ready to go now? Or @jseyfried/@eddyb were there reservations?

[eddyb]

r? @jseyfried

[jseyfried]

@goffrie Looks good, thanks!
Sorry for the delay -- Github doesn't notify people subscribed to PR on force push.

@bors r+

[bors]

📌 Commit eed86fa has been approved by jseyfried

[bors]

⌛ Testing commit eed86fa with merge 4da129d...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-cargotest, auto-linux-64-cross-freebsd, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-opt, auto-mac-64-opt-rustbuild, auto-mac-cross-ios-opt, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-cargotest, auto-win-msvc-64-opt, auto-win-msvc-64-opt-rustbuild
Approved by: jseyfried
Pushing 4da129d to master...