TranslateError could have better formatting

[matthiaskrgr]

I'm not sure if this is intentional

error: expected expression, found `,`
 --> /home/matthias/vcs/github/glacier2/fixed/94629.rs:2:40
  |
2 |     fn a(){{{{({{{ExprKind::Use {});(]),}}
  |                                        ^ expected expression

thread 'rustc' panicked at 'called `Result::unwrap()` on an `Err` value: failed while formatting fluent string `parse_mismatched_closing_delimiter`:
message was missing
', compiler/rustc_errors/src/emitter.rs:1391:84
stack backtrace:
   0:     0x7f9840cf51e1 - std::backtrace_rs::backtrace::libunwind::trace::hd0b11c0adaab3249
                               at /home/matthias/vcs/github/rust_debug_assertions/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7f9840cf51e1 - std::backtrace_rs::backtrace::trace_unsynchronized::h700e400a91d91fde
                               at /home/matthias/vcs/github/rust_debug_assertions/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f9840cf51e1 - std::sys_common::backtrace::_print_fmt::hc78435809ad4efce
                               at /home/matthias/vcs/github/rust_debug_assertions/library/std/src/sys_common/backtrace.rs:65:5
   3:     0x7f9840cf51e1 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::ha735a792fef532f5
                               at /home/matthias/vcs/github/rust_debug_assertions/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f9840d6bae8 - core::fmt::write::h4891dd9bd07e2ad5

Looks like we print `{stringname}`:\n{message}\n', ....
Might be better to just put everything in one line..?

You might need debug assertion to repro these ICEs in the first place.

[mejrs]

The relevant code is here

Might be better to just put everything in one line..?

I'm not sure. Some variants of the error have much longer messages and I wouldn't like to squash everything to one line.

[matthiaskrgr]

Yeah, I saw it would writeLN everyhing which might be part of the problem 😅
Maybe we could oneline the error if it has less than 20 chars or something? 🤷

[ts0yu]

can i take this as my first contribution? i might need some guidance but i think i have a good idea of where to start.

[ts0yu]

@rustbot claim

[mejrs]

can i take this as my first contribution? i might need some guidance but i think i have a good idea of where to start.

If you think this is worth changing (personally I am neither for or against), then sure!

You probably want to change some of the writeln!s to write!. Then you can update/add to the tests at https://github.com/rust-lang/rust/blob/5e37043d63bfe2f3be8fa5a05b07d6c0dad5775d/compiler/rustc_errors/src/tests.rs

Something to keep in mind is that Report is used

rust/compiler/rustc_errors/src/translation.rs

Lines 49 to 51 in 5e37043

	.iter()
	.map(|(m, _)| self.translate_message(m, args).map_err(Report::new).unwrap())
	.collect::<String>(),

to forward from its Debug impl (that's what unwrap uses) to Display. You might want to keep that in mind if you decide to customize the Debug impl rather than changing Display