This makes it easier to open the messages file while developing on features.
The commit was the result of automatted changes:
for p in compiler/rustc_*; do mv $p/locales/en-US.ftl $p/messages.ftl; rmdir $p/locales; done
for p in compiler/rustc_*; do sed -i "s#\.\./locales/en-US.ftl#../messages.ftl#" $p/src/lib.rs; done
statically guarantee that current error codes are documented
Closes#61137 (that's right!)
Pretty simple refactor (often just a change from `Result<Option<&str>>` to `Result<&str>`)
r? `@GuillaumeGomez` (could you specially look at 53044158eff0d64673a6100f701c57b484232aca? I believe you wrote that in the first place, just want to make sure you're happy with the change)
Add `ErrorGuaranteed` to `hir::{Expr,Ty}Kind::Err` variants
First step in making the `Err` variants of `ExprKind` and `TyKind` require an `ErrorGuaranteed` during parsing. Making the corresponding AST versions require `ErrorGuaranteed` is a bit harder, whereas it was pretty easy to do this for HIR, so let's do that first.
The only weird thing about this PR is that `ErrorGuaranteed` is moved to `rustc_span`. This is *certainly* not the right place to put it, but `rustc_hir` cannot depend on `rustc_error` because the latter already depends on the former. Should I just pull out some of the error machinery from `rustc_error` into an even more minimal crate that `rustc_hir` can depend on? Advice would be appreciated.
Extend `CodegenBackend` trait with a function returning the translation
resources from the codegen backend, which can be added to the complete
list of resources provided to the emitter.
Signed-off-by: David Wood <david.wood@huawei.com>
`run-make/translation` had some targets that weren't listed in `all` and
thus weren't being tested - the behaviour that should have been being
tested was basically correct fortunately.
Signed-off-by: David Wood <david.wood@huawei.com>
Instead of loading the Fluent resources for every crate in
`rustc_error_messages`, each crate generates typed identifiers for its
own diagnostics and creates a static which are pulled together in the
`rustc_driver` crate and provided to the diagnostic emitter.
Signed-off-by: David Wood <david.wood@huawei.com>
Don't recover lifetimes/labels containing emojis as character literals
Fixes#108019.
Note that at the time of this commit, `unic-emoji-char` seems to have data tables only up to Unicode 5.0, but Unicode is already newer than this.
A newer emoji such as `🥺` will not be recognized as an emoji but older emojis such as `🐱` will.
This PR leaves a couple of FIXMEs where `unic_emoji_char::is_emoji` is used.
Note that at the time of this commit, `unic-emoji-char` seems to have
data tables only up to Unicode 5.0, but Unicode is already newer than
this.
A newer emoji such as `🥺` will not be recognized as an emoji
but older emojis such as `🐱` will.
Introduce `-Zterminal-urls` to use OSC8 for error codes
Terminals supporting the OSC8 Hyperlink Extension can support inline anchors where the text is user defineable but clicking on it opens a browser to a specified URLs, just like `<a href="URL">` does in HTML.
https://gist.github.com/egmontkob/eb114294efbcd5adb1944c9f3cb5feda
Terminals supporting the OSC8 Hyperlink Extension can support inline
anchors where the text is user defineable but clicking on it opens a
browser to a specified URLs, just like `<a href="URL">` does in HTML.
https://gist.github.com/egmontkob/eb114294efbcd5adb1944c9f3cb5feda
Implement `IntoDiagnosticArg` for `&'a T` when `T` implements
`IntoDiagnosticArg` and `Clone`. Makes it easier to write diagnostic
structs that borrow something which implements `IntoDiagnosticArg`.
Signed-off-by: David Wood <david.wood@huawei.com>
Support for emission of notes was added in f8ebc72 but `emit_note` and
`create_note` functions weren't added to `Handler`.
Signed-off-by: David Wood <david.wood@huawei.com>
Collect and emit proper backtraces for `delay_span_bug`s
This is a follow-up to #106317, which addresses this comment (https://github.com/rust-lang/rust/issues/106267#issuecomment-1367507507) which notes that `delay_span_bug`s' backtraces are nonsense.
Captures and emits the backtrace of the delayed span bug when it's *created*, rather than using the backtrace of the place where delayed bugs are flushed.
---
To test, I delayed a span bug during HIR typeck, specifically in `typeck_with_fallback`...
Before, note `flush_delayed` on frame 18. This is at the end of the compilation session, far from where the bug is being delayed.
```
error: internal compiler error: test
--> /home/ubuntu/test.rs:1:1
|
1 | fn main() {}
| ^^^^^^^^^
|
= note: delayed at compiler/rustc_hir_typeck/src/lib.rs:196:14
thread 'rustc' panicked at 'Box<dyn Any>', compiler/rustc_errors/src/lib.rs:1634:13
stack backtrace:
0: 0x7f9c3ec69dd1 - std::backtrace_rs::backtrace::libunwind::trace::h26056f81198c6594
at /home/ubuntu/rust2/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
1: 0x7f9c3ec69dd1 - std::backtrace_rs::backtrace::trace_unsynchronized::hacfb345a0c6d5bb1
at /home/ubuntu/rust2/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
2: 0x7f9c3ec69dd1 - std::sys_common::backtrace::_print_fmt::h18ea6016ac8030f3
at /home/ubuntu/rust2/library/std/src/sys_common/backtrace.rs:65:5
3: 0x7f9c3ec69dd1 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::he35dde201d0c2d09
at /home/ubuntu/rust2/library/std/src/sys_common/backtrace.rs:44:22
4: 0x7f9c3ecee308 - core::fmt::write::h094ad263467a053c
at /home/ubuntu/rust2/library/core/src/fmt/mod.rs:1208:17
5: 0x7f9c3ec8aaf1 - std::io::Write::write_fmt::hd47b4e2324b4d9b7
at /home/ubuntu/rust2/library/std/src/io/mod.rs:1682:15
6: 0x7f9c3ec69bfa - std::sys_common::backtrace::_print::h43044162653a17fc
at /home/ubuntu/rust2/library/std/src/sys_common/backtrace.rs:47:5
7: 0x7f9c3ec69bfa - std::sys_common::backtrace::print::hc8605da258fa5aeb
at /home/ubuntu/rust2/library/std/src/sys_common/backtrace.rs:34:9
8: 0x7f9c3ec4db87 - std::panicking::default_hook::{{closure}}::h9e37f23f75122a15
9: 0x7f9c3ec4d97b - std::panicking::default_hook::h602873a063f84da2
at /home/ubuntu/rust2/library/std/src/panicking.rs:286:9
10: 0x7f9c3f6672b2 - <alloc[48d7b30605060536]::boxed::Box<dyn for<'a, 'b> core[672e3947e150d6c6]::ops::function::Fn<(&'a core[672e3947e150d6c6]::panic::panic_info::PanicInfo<'b>,), Output = ()> + core[672e3947e150d6c6]::marker::Send + core[672e3947e150d6c6]::marker::Sync> as core[672e3947e150d6c6]::ops::function::Fn<(&core[672e3947e150d6c6]::panic::panic_info::PanicInfo,)>>::call
at /home/ubuntu/rust2/library/alloc/src/boxed.rs:2002:9
11: 0x7f9c3f6672b2 - rustc_driver[f5b6d32d8905ecdd]::DEFAULT_HOOK::{closure#0}::{closure#0}
at /home/ubuntu/rust2/compiler/rustc_driver/src/lib.rs:1204:17
12: 0x7f9c3ec4e0d3 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hfd13333ca953ae8e
at /home/ubuntu/rust2/library/alloc/src/boxed.rs:2002:9
13: 0x7f9c3ec4e0d3 - std::panicking::rust_panic_with_hook::h45753e10264ebe7e
at /home/ubuntu/rust2/library/std/src/panicking.rs:692:13
14: 0x7f9c422a1aa3 - std[3330b4673efabfce]::panicking::begin_panic::<rustc_errors[1b15f4e7e49d1fd5]::ExplicitBug>::{closure#0}
at /home/ubuntu/rust2/library/std/src/panicking.rs:608:9
15: 0x7f9c422a1a46 - std[3330b4673efabfce]::sys_common::backtrace::__rust_end_short_backtrace::<std[3330b4673efabfce]::panicking::begin_panic<rustc_errors[1b15f4e7e49d1fd5]::ExplicitBug>::{closure#0}, !>
at /home/ubuntu/rust2/library/std/src/sys_common/backtrace.rs:137:18
16: 0x7f9c3f63a996 - std[3330b4673efabfce]::panicking::begin_panic::<rustc_errors[1b15f4e7e49d1fd5]::ExplicitBug>
at /home/ubuntu/rust2/library/std/src/panicking.rs:607:12
17: 0x7f9c4227a496 - std[3330b4673efabfce]::panic::panic_any::<rustc_errors[1b15f4e7e49d1fd5]::ExplicitBug>
at /home/ubuntu/rust2/library/std/src/panic.rs:61:5
18: 0x7f9c4227cdf7 - <rustc_errors[1b15f4e7e49d1fd5]::HandlerInner>::flush_delayed::<alloc[48d7b30605060536]::vec::Vec<rustc_errors[1b15f4e7e49d1fd5]::diagnostic::Diagnostic>, &str, rustc_errors[1b15f4e7e49d1fd5]::ExplicitBug>
at /home/ubuntu/rust2/compiler/rustc_errors/src/lib.rs:1634:13
19: 0x7f9c422498cf - <rustc_errors[1b15f4e7e49d1fd5]::Handler>::flush_delayed
at /home/ubuntu/rust2/compiler/rustc_errors/src/lib.rs:1225:9
[ FRAMES INTENTIONALLY OMITTED ]
44: 0x7f9c3f6f3584 - <std[3330b4673efabfce]:🧵:Builder>::spawn_unchecked_::<rustc_interface[947706ead88047d0]::util::run_in_thread_pool_with_globals<rustc_interface[947706ead88047d0]::interface::run_compiler<core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>, rustc_driver[f5b6d32d8905ecdd]::run_compiler::{closure#1}>::{closure#0}, core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>>::{closure#1}
at /home/ubuntu/rust2/library/std/src/thread/mod.rs:549:30
45: 0x7f9c3f6f3584 - <<std[3330b4673efabfce]:🧵:Builder>::spawn_unchecked_<rustc_interface[947706ead88047d0]::util::run_in_thread_pool_with_globals<rustc_interface[947706ead88047d0]::interface::run_compiler<core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>, rustc_driver[f5b6d32d8905ecdd]::run_compiler::{closure#1}>::{closure#0}, core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>>::{closure#1} as core[672e3947e150d6c6]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
at /home/ubuntu/rust2/library/core/src/ops/function.rs:250:5
46: 0x7f9c3ec81968 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::he8b26fc22c6f51ec
at /home/ubuntu/rust2/library/alloc/src/boxed.rs:1988:9
47: 0x7f9c3ec81968 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h5cf9cbe75a8c3ddc
at /home/ubuntu/rust2/library/alloc/src/boxed.rs:1988:9
48: 0x7f9c3ec5f99c - std::sys::unix:🧵:Thread:🆕:thread_start::h2d6dd4455e97d031
at /home/ubuntu/rust2/library/std/src/sys/unix/thread.rs:108:17
49: 0x7f9c37c69609 - start_thread
50: 0x7f9c3ead0133 - clone
51: 0x0 - <unknown>
```
After, note `typeck_with_fallback` on the 5th frame, that's where we *actually* need to be pointed to:
```
error: internal compiler error: no errors encountered even though `delay_span_bug` issued
error: internal compiler error: test
--> /home/ubuntu/test.rs:1:1
|
1 | fn main() {}
| ^^^^^^^^^
|
= note: delayed at 0: <rustc_errors::HandlerInner>::emit_diagnostic
at ./compiler/rustc_errors/src/lib.rs:1279:29
1: <rustc_errors::HandlerInner>::delay_span_bug::<rustc_span::span_encoding::Span, &str>
at ./compiler/rustc_errors/src/lib.rs:1553:9
2: <rustc_errors::Handler>::delay_span_bug::<rustc_span::span_encoding::Span, &str>
at ./compiler/rustc_errors/src/lib.rs:995:9
3: <rustc_session::session::Session>::delay_span_bug::<rustc_span::span_encoding::Span, &str>
at ./compiler/rustc_session/src/session.rs:600:9
4: rustc_hir_typeck::typeck_with_fallback::<rustc_hir_typeck::typeck::{closure#0}>::{closure#0}
at ./compiler/rustc_hir_typeck/src/lib.rs:196:5
5: rustc_hir_typeck::typeck_with_fallback::<rustc_hir_typeck::typeck::{closure#0}>
at ./compiler/rustc_hir_typeck/src/lib.rs:185:36
6: rustc_hir_typeck::typeck
at ./compiler/rustc_hir_typeck/src/lib.rs:166:9
[ FRAMES INTENTIONALLY OMITTED ]
108: std::panicking::try::<core::result::Result<(), rustc_errors::ErrorGuaranteed>, core::panic::unwind_safe::AssertUnwindSafe<<std:🧵:Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#1}::{closure#0}>>
at ./library/std/src/panicking.rs:447:19
109: std::panic::catch_unwind::<core::panic::unwind_safe::AssertUnwindSafe<<std:🧵:Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#1}::{closure#0}>, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
at ./library/std/src/panic.rs:140:14
110: <std:🧵:Builder>::spawn_unchecked_::<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#1}
at ./library/std/src/thread/mod.rs:549:30
111: <<std:🧵:Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
at ./library/core/src/ops/function.rs:250:5
112: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
at ./library/alloc/src/boxed.rs:1988:9
113: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
at ./library/alloc/src/boxed.rs:1988:9
114: std::sys::unix:🧵:Thread:🆕:thread_start
at ./library/std/src/sys/unix/thread.rs:108:17
115: start_thread
116: clone
```
Migrate `codegen_ssa` to diagnostics structs - [Part 3]
Completes migrating `codegen_ssa` module except 2 outstanding errors that depend on other crates:
1. [`rustc_middle::mir::interpret::InterpError`](b6097f2e1b/compiler/rustc_middle/src/mir/interpret/error.rs (L475)): I saw `rustc_middle` is unassigned, I am open to take this work.
2. `codegen_llvm`'s use of `fn span_invalid_monomorphization_error`, which I started to replace in the [last commit](9a31b3cdda) of this PR, but would like to know the team's preference on how we should keep replacing the other macros:
2.1. Update macros to expect a `Diagnostic`
2.2. Remove macros and expand the code on each use.
See [some examples of the different options in this experimental commit](64aee83e80)
_Part 2 - https://github.com/rust-lang/rust/pull/103792_
r? ``@davidtwco``
Cc ``@compiler-errors``
Encode spans relative to the enclosing item -- enable on nightly
Follow-up to #84373 with the flag `-Zincremental-relative-spans` set by default.
This PR seeks to remove one of the main shortcomings of incremental: the handling of spans.
Changing the contents of a function may require redoing part of the compilation process for another function in another file because of span information is changed.
Within one file: all the spans in HIR change, so typechecking had to be re-done.
Between files: spans of associated types/consts/functions change, so type-based resolution needs to be re-done (hygiene information is stored in the span).
The flag `-Zincremental-relative-spans` encodes local spans relative to the span of an item, stored inside the `source_span` query.
Trap: stashed diagnostics are referenced by the "raw" span, so stealing them requires to remove the span's parent.
In order to avoid too much traffic in the span interner, span encoding uses the `ctxt_or_tag` field to encode:
- the parent when the `SyntaxContext` is 0;
- the `SyntaxContext` when the parent is `None`.
Even with this, the PR creates a lot of traffic to the Span interner, when a Span has both a LocalDefId parent and a non-root SyntaxContext. They appear in lowering, when we add a parent to all spans, including those which come from macros, and during inlining when we mark inlined spans.
The last commit changes how queries of `LocalDefId` manage their cache. I can put this in a separate PR if required.
Possible future directions:
- validate that all spans are marked in HIR validation;
- mark macro-expanded spans relative to the def-site and not the use-site.
compiler: remove unnecessary imports and qualified paths
Some of these imports were necessary before Edition 2021, others were already in the prelude.
I hope it's fine that this PR is so spread-out across files :/
This migrates everything but the `mbe` and `proc_macro` modules. It also
contains a few cleanups and drive-by/accidental diagnostic improvements
which can be seen in the diff for the UI tests.
make `error_reported` check for delayed bugs
Fixes#104768
`error_reported()` was only checking if there were errors emitted, not for `delay_bug`s which can also be a source of `ErrorGuaranteed`. I assume the same is true of `lint_err_count` but i dont know
Use `as_deref` in compiler (but only where it makes sense)
This simplifies some code :3
(there are some changes that are not exacly `as_deref`, but more like "clever `Option`/`Result` method use")
Add a detailed note for missing comma typo w/ FRU syntax
Thanks to `@pierwill` for working on this with me!
Fixes#104373, perhaps `@alice-i-cecile` can comment on the new error for the example provided on that issue -- feedback is welcome.
```
error[E0063]: missing field `defaulted` in initializer of `Outer`
--> $DIR/multi-line-fru-suggestion.rs:14:5
|
LL | Outer {
| ^^^^^ missing `defaulted`
|
note: this expression may have been misinterpreted as a `..` range expression
--> $DIR/multi-line-fru-suggestion.rs:16:16
|
LL | inner: Inner {
| ________________^
LL | | a: 1,
LL | | b: 2,
LL | | }
| |_________^ this expression does not end in a comma...
LL | ..Default::default()
| ^^^^^^^^^^^^^^^^^^^^ ... so this is interpreted as a `..` range expression, instead of functional record update syntax
help: to set the remaining fields from `Default::default()`, separate the last named field with a comma
|
LL | },
| +
error: aborting due to previous error
For more information about this error, try `rustc --explain E0063`.
```
Use `IsTerminal` in place of `atty`
In any crate that can use nightly features, use `IsTerminal` rather than
`atty`:
- Use `IsTerminal` in `rustc_errors`
- Use `IsTerminal` in `rustc_driver`
- Use `IsTerminal` in `rustc_log`
- Use `IsTerminal` in `librustdoc`
Rollup of 8 pull requests
Successful merges:
- #102977 (remove HRTB from `[T]::is_sorted_by{,_key}`)
- #103378 (Fix mod_inv termination for the last iteration)
- #103456 (`unchecked_{shl|shr}` should use `u32` as the RHS)
- #103701 (Simplify some pointer method implementations)
- #104047 (Diagnostics `icu4x` based list formatting.)
- #104338 (Enforce that `dyn*` coercions are actually pointer-sized)
- #104498 (Edit docs for `rustc_errors::Handler::stash_diagnostic`)
- #104556 (rustdoc: use `code-header` class to format enum variants)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Edit docs for `rustc_errors::Handler::stash_diagnostic`
Clarify that the diagnostic can be retrieved with `steal_diagnostic`.
r? ```@compiler-errors```
Don't print full paths in overlap errors
We don't print the full path in other diagnostics -- I don't think it particularly helps with the error message. I also delayed the printing until actually needing to render the error message.
r? diagnostics
implement binding_shadows
migrate till self-in-generic-param-default
use braces in fluent message as suggested by @compiler-errors.
to fix lock file issue reported by CI
migrate 'unreachable label' error
run formatter
name the variables correctly in fluent file
SessionDiagnostic -> Diagnostic
test "pattern/pat-tuple-field-count-cross.rs" passed
test "resolve/bad-env-capture2.rs" passed
test "enum/enum-in-scope.rs" and other depended on "resolve_binding_shadows_something_unacceptable" should be passed now.
fix crash errors while running test-suite. there might be more.
then_some(..) suits better here.
all tests passed
convert TraitImpl and InvalidAsm. TraitImpl is buggy yet. will fix after receiving help from Zulip
migrate "Ralative-2018"
migrate "ancestor only"
migrate "expected found"
migrate "Indeterminate"
migrate "module only"
revert to the older implementation for now. since this is failing at the moment.
follow the convension for fluent variable
order the diag attribute as suggested in review comment
fix merge error. migrate trait-impl-duplicate
make the changes compatible with "Flatten diagnostic slug modules #103345"
fix merge
remove commented code
merge issues
fix review comments
fix tests
Display help message when fluent arg was referenced incorrectly
The fluent argument syntax is a little special and easy to get wrong, so we emit a small help message when someone gets it wrong.
Example:
```
parser_mismatched_closing_delimiter = mismatched closing delimiter: `${delimiter}`
```
panics with
```
thread 'rustc' panicked at 'Encountered errors while formatting message for `parser_mismatched_closing_delimiter`
help: Argument `delimiter` exists but was not referenced correctly. Try using `{$delimiter}` instead
attr: `None`
args: `FluentArgs([("delimiter", String("}"))])`
errors: `[ResolverError(Reference(Message { id: "delimiter", attribute: None }))]`', compiler/rustc_errors/src/translation.rs:123:21
```
fixes#103539
Some diagnostic-related nits
1. Use `&mut Diagnostic` instead of `&mut DiagnosticBuilder<'_, T>`
2. Make `diag.span_suggestions` take an `IntoIterator` instead of `Iterator`, just to remove some `.into_iter` calls on the caller.
idk if I should add a lint to make sure people use `&mut Diagnostic` instead of `&mut DiagnosticBuilder<'_, T>` in cases where we're just, e.g., adding subdiagnostics to the diagnostic... maybe a followup.
The fluent argument syntax is a little special and easy to get wrong, so
we emit a small help message when someone gets it wrong.
Example:
```
parser_mismatched_closing_delimiter = mismatched closing delimiter: `${delimiter}`
```
panics with
```
thread 'rustc' panicked at 'Encountered errors while formatting message for `parser_mismatched_closing_delimiter`
help: Argument `delimiter` exists but was not referenced correctly. Try using `{$delimiter}` instead
attr: `None`
args: `FluentArgs([("delimiter", String("}"))])`
errors: `[ResolverError(Reference(Message { id: "delimiter", attribute: None }))]`', compiler/rustc_errors/src/translation.rs:123:21
```
