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`
Port `dead_code` lints to be translatable.
This adds an additional comma to lists with three or more items, to be consistent with list formatters like `icu4x`.
r? `@davidtwco`
Track where diagnostics were created.
This implements the `-Ztrack-diagnostics` flag, which uses `#[track_caller]` to track where diagnostics are created. It is meant as a debugging tool much like `-Ztreat-err-as-bug`.
For example, the following code...
```rust
struct A;
struct B;
fn main(){
let _: A = B;
}
```
...now emits the following error message:
```
error[E0308]: mismatched types
--> src\main.rs:5:16
|
5 | let _: A = B;
| - ^ expected struct `A`, found struct `B`
| |
| expected due to this
-Ztrack-diagnostics: created at compiler\rustc_infer\src\infer\error_reporting\mod.rs:2275:31
```
translation: eager translation
Part of #100717. See [Zulip thread](https://rust-lang.zulipchat.com/#narrow/stream/336883-i18n/topic/.23100717.20lists!/near/295010720) for additional context.
- **Store diagnostic arguments in a `HashMap`**: Eager translation will enable subdiagnostics to be translated multiple times with different arguments - this requires the ability to replace the value of one argument with a new value, which is better suited to a `HashMap` than the previous storage, a `Vec`.
- **Add `AddToDiagnostic::add_to_diagnostic_with`**: `AddToDiagnostic::add_to_diagnostic_with` is similar to the previous `AddToDiagnostic::add_to_diagnostic` but takes a function that can be used by the caller to modify diagnostic messages originating from the subdiagnostic (such as performing translation eagerly). `add_to_diagnostic` now just calls `add_to_diagnostic_with` with an empty closure.
- **Add `DiagnosticMessage::Eager`**: Add variant of `DiagnosticMessage` for eagerly translated messages
(messages in the target language which don't need translated by the emitter during emission). Also adds `eager_subdiagnostic` function which is intended to be invoked by the diagnostic derive for subdiagnostic fields which are marked as needing eager translation.
- **Support `#[subdiagnostic(eager)]`**: Add support for `eager` argument to the `subdiagnostic` attribute which generates a call to `eager_subdiagnostic`.
- **Finish migrating `rustc_query_system`**: Using eager translation, migrate the remaining repeated cycle stack diagnostic.
- **Split formatting initialization and use in diagnostic derives**: Diagnostic derives have previously had to take special care when ordering the generated code so that fields were not used after a move.
This is unlikely for most fields because a field is either annotated with a subdiagnostic attribute and is thus likely a `Span` and copiable, or is a argument, in which case it is only used once by `set_arg`
anyway.
However, format strings for code in suggestions can result in fields being used after being moved if not ordered carefully. As a result, the derive currently puts `set_arg` calls last (just before emission), such as:
let diag = { /* create diagnostic */ };
diag.span_suggestion_with_style(
span,
fluent::crate::slug,
format!("{}", __binding_0),
Applicability::Unknown,
SuggestionStyle::ShowAlways
);
/* + other subdiagnostic additions */
diag.set_arg("foo", __binding_0);
/* + other `set_arg` calls */
diag.emit();
For eager translation, this doesn't work, as the message being translated eagerly can assume that all arguments are available - so arguments _must_ be set first.
Format strings for suggestion code are now separated into two parts - an initialization line that performs the formatting into a variable, and a usage in the subdiagnostic addition.
By separating these parts, the initialization can happen before arguments are set, preserving the desired order so that code compiles, while still enabling arguments to be set before subdiagnostics are added.
let diag = { /* create diagnostic */ };
let __code_0 = format!("{}", __binding_0);
/* + other formatting */
diag.set_arg("foo", __binding_0);
/* + other `set_arg` calls */
diag.span_suggestion_with_style(
span,
fluent::crate::slug,
__code_0,
Applicability::Unknown,
SuggestionStyle::ShowAlways
);
/* + other subdiagnostic additions */
diag.emit();
- **Remove field ordering logic in diagnostic derive:** Following the approach taken in earlier commits to separate formatting initialization from use in the subdiagnostic derive, simplify the diagnostic derive by removing the field-ordering logic that previously solved this problem.
r? ```@compiler-errors```
Migrate rustc_passes diagnostics
Picks up abandoned work from https://github.com/rust-lang/rust/pull/100870
I would like to do this collaboratively, as there is a lot of work! Here's the process:
- Comment below that you are willing to help and I will add you as a collaborator to my `rust` fork (that gives you write access)
- Indicate which file/task you would like to work on (so we don't duplicate work) from the list below
- Do the work, push up a commit, comment that you're done with that file/task
- Repeat until done 😄
### Files to Migrate (in `compiler/rustc_passes/src/`)
- [x] check_attr.rs ``@CleanCut``
- [x] check_const.rs ``@CleanCut``
- [x] dead.rs ``@CleanCut``
- [x] debugger_visualizer.rs ``@CleanCut``
- [x] diagnostic_items.rs ``@CleanCut``
- [x] entry.rs ``@CleanCut``
- [x] lang_items.rs ``@CleanCut``
- [x] layout_test.rs ``@CleanCut``
- [x] lib_features.rs ``@CleanCut``
- [x] ~liveness.rs~ ``@CleanCut`` Nothing to do
- [x] loops.rs ``@CleanCut``
- [x] naked_functions.rs ``@CleanCut``
- [x] stability.rs ``@CleanCut``
- [x] weak_lang_items.rs ``@CleanCut``
### Tasks
- [x] Rebase on current `master` ``@CleanCut``
- [x] Review work from [the earlier PR](https://github.com/rust-lang/rust/pull/100870) and make sure it all looks good
- [x] compiler/rustc_error_messages/locales/en-US/passes.ftl ``@CleanCut``
- [x] compiler/rustc_passes/src/check_attr.rs ``@CleanCut``
- [x] compiler/rustc_passes/src/errors.rs ``@CleanCut``
- [x] compiler/rustc_passes/src/lang_items.rs ``@CleanCut``
- [x] compiler/rustc_passes/src/lib.rs ``@CleanCut``
- [x] compiler/rustc_passes/src/weak_lang_items.rs ``@CleanCut``
Add variant of `DiagnosticMessage` for eagerly translated messages
(messages in the target language which don't need translated by the
emitter during emission). Also adds `eager_subdiagnostic` function which
is intended to be invoked by the diagnostic derive for subdiagnostic
fields which are marked as needing eager translation.
Signed-off-by: David Wood <david.wood@huawei.com>
Add `Noted` marker struct that implements `EmissionGuarantee` so that
`emit_note` and `create_note` can be implemented for struct diagnostics.
Signed-off-by: David Wood <david.wood@huawei.com>
Move lint level source explanation to the bottom
So, uhhhhh
r? `@estebank`
## User-facing change
"note: `#[warn(...)]` on by default" and such are moved to the bottom of the diagnostic:
```diff
- = note: `#[warn(unsupported_calling_conventions)]` on by default
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #87678 <https://github.com/rust-lang/rust/issues/87678>
+ = note: `#[warn(unsupported_calling_conventions)]` on by default
```
Why warning is enabled is the least important thing, so it shouldn't be the first note the user reads, IMO.
## Developer-facing change
`struct_span_lint` and similar methods have a different signature.
Before: `..., impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>)`
After: `..., impl Into<DiagnosticMessage>, impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>) -> &'b mut DiagnosticBuilder<'a, ()>`
The reason for this is that `struct_span_lint` needs to edit the diagnostic _after_ `decorate` closure is called. This also makes lint code a little bit nicer in my opinion.
Another option is to use `impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>) -> DiagnosticBuilder<'a, ()>` altough I don't _really_ see reasons to do `let lint = lint.build(message)` everywhere.
## Subtle problem
By moving the message outside of the closure (that may not be called if the lint is disabled) `format!(...)` is executed earlier, possibly formatting `Ty` which may call a query that trims paths that crashes the compiler if there were no warnings...
I don't think it's that big of a deal, considering that we move from `format!(...)` to `fluent` (which is lazy by-default) anyway, however this required adding a workaround which is unfortunate.
## P.S.
I'm sorry, I do not how to make this PR smaller/easier to review. Changes to the lint API affect SO MUCH 😢
Group together more size assertions.
Also add a few more assertions for some relevant token-related types.
And fix an erroneous comment in `rustc_errors`.
r? `@lqd`
Flush delayed bugs before codegen
Sometimes it can happen that invalid code like a TyKind::Error makes its way through the compiler without triggering any errors (this is always a bug in rustc but bugs do happen sometimes :)). These ICEs will manifest in the backend like as cg_llvm not being able to get the layout of `[type error]`, which makes it hard to debug. By flushing before codegen, we display all the delayed bugs, making it easier to trace it to the root of the problem.
I tried this on #102366 and it showed tons of of delayed bugs and no error in cg_llvm, so it seems to be working.
Sometimes it can happen that invalid code like a TyKind::Error makes
its way through the compiler without triggering any errors (this is
always a bug in rustc but bugs do happen sometimes :)). These ICEs
will manifest in the backend like as cg_llvm not being able to get
the layout of `[type error]`, which makes it hard to debug. By flushing
before codegen, we display all the delayed bugs, making it easier to
trace it to the root of the problem.
`parse_token_tree` is basically a match with four arms: `Eof`,
`OpenDelim`, `CloseDelim`, and "other". It has two call sites, and at
each call site one of the arms is unreachable. It's also not inlined.
This commit removes `parse_token_tree` by splitting it into four
functions and inlining them. This avoids some repeated conditional
tests and also some non-inlined function calls on the hot path.
FIX - ambiguous Diagnostic link in docs
UPDATE - rename diagnostic_items to IntoDiagnostic and AddToDiagnostic
[Gardening] FIX - formatting via `x fmt`
FIX - rebase conflicts. NOTE: Confirm wheather or not we want to handle TargetDataLayoutErrorsWrapper this way
DELETE - unneeded allow attributes in Handler method
FIX - broken test
FIX - Rebase conflict
UPDATE - rename residual _SessionDiagnostic and fix LintDiag link
On later stages, the feature is already stable.
Result of running:
rg -l "feature.let_else" compiler/ src/librustdoc/ library/ | xargs sed -s -i "s#\\[feature.let_else#\\[cfg_attr\\(bootstrap, feature\\(let_else\\)#"
Make call suggestions more general and more accurate
Cleans up some suggestions that have to do with adding `()` to make typeck happy.
1. Drive-by rename of `expr_t` to `base_ty` since it's the type of the `base_expr`
1. Autoderef until we get to a callable type in `suggest_fn_call`.
1. Don't erroneously suggest calling constructor when a method/field does not exist on it.
1. Suggest calling a method receiver if its function output has a method (e.g. `fn.method()` => `fn().method()`)
1. Extend call suggestions to type parameters, fn pointers, trait objects where possible
1. Suggest calling in operators too (fixes#101054)
1. Use `/* {ty} */` as argument placeholder instead of just `_`, which is confusing and makes suggestions look less like `if let` syntax.
Reenable disabled early syntax gates as future-incompatibility lints
- MCP: https://github.com/rust-lang/compiler-team/issues/535
The approach taken by this PR is
- Introduce a new lint, `unstable_syntax_pre_expansion`, and reenable the early syntax gates to emit it
- Use the diagnostic stashing mechanism to stash warnings the early warnings
- When the hard error occurs post expansion, steal and cancel the early warning
- Don't display any stashed warnings if errors are present to avoid the same noise problem that hiding type ascription errors is avoiding
Commits are working commits, but in a coherent steps-to-implement manner. Can be squashed if desired.
The preexisting `soft_unstable` lint seems like it would've been a good fit, but it is deny-by-default (appropriate for `#[bench]`) and these gates should be introduced as warn-by-default.
It may be desirable to change the stash mechanism's behavior to not flush lint errors in the presence of other errors either (like is done for warnings here), but upgrading a stash-using lint from warn to error perhaps is enough of a request to see the lint that they shouldn't be hidden; additionally, fixing the last error to get new errors thrown at you always feels bad, so if we know the lint errors are present, we should show them.
Using a new flag/mechanism for a "weak diagnostic" which is suppressed by other errors may also be desirable over assuming any stashed warnings are "weak," but this is the first user of stashing warnings and seems an appropriate use of stashing (it follows the "know more later to refine the diagnostic" pattern; here we learn that it's in a compiled position) so we get to define what it means to stash a non-hard-error diagnostic.
cc `````@petrochenkov````` (seconded MCP)
triagebot: add translation-related mention groups
- Move some code around so that triagebot can ping relevant parties when translation logic is modified.
- Add mention groups to triagebot for translation-related files/folders.
- Auto-label pull requests with changes to translation-related files/folders with `A-translation`.
r? `@Mark-Simulacrum`
Just moving code around so that triagebot can ping relevant parties when
translation logic is modified.
Signed-off-by: David Wood <david.wood@huawei.com>
If a primary bundle doesn't contain a message then the fallback bundle
is used. However, if the primary bundle's message is broken (e.g. it
refers to a interpolated variable that the compiler isn't providing)
then this would just result in a compiler panic. While there aren't any
primary bundles right now, this is the type of issue that could come up
once translation is further along.
Signed-off-by: David Wood <david.wood@huawei.com>
Stabilize backtrace
This PR stabilizes the std::backtrace module. As of #99431, the std::Error::backtrace item has been removed, and so the rest of the backtrace feature is set to be stabilized.
Previous discussion can be found in #72981, #3156.
Stabilized API summary:
```rust
pub mod std {
pub mod backtrace {
pub struct Backtrace { }
pub enum BacktraceStatus {
Unsupported,
Disabled,
Captured,
}
impl fmt::Debug for Backtrace {}
impl Backtrace {
pub fn capture() -> Backtrace;
pub fn force_capture() -> Backtrace;
pub const fn disabled() -> Backtrace;
pub fn status(&self) -> BacktraceStatus;
}
impl fmt::Display for Backtrace {}
}
}
```
`@yaahc`
Hide irrelevant lines in suggestions to allow for suggestions that are far from each other to be shown
This is an attempt to fix suggestions one part of which is 6 lines or more far from the first. I've noticed "the problem" (of not showing some parts of the suggestion) here: https://github.com/rust-lang/rust/pull/97759#discussion_r889689230.
I'm not sure about the implementation (this big closure is just bad and makes already complicated code even more so), but I want to at least discuss the result.
Here is an example of how this changes the output:
Before:
```text
help: consider enclosing expression in a block
|
3 ~ 'l: { match () { () => break 'l,
4 |
5 |
6 |
7 |
8 |
...
```
After:
```text
help: consider enclosing expression in a block
|
3 ~ 'l: { match () { () => break 'l,
4 |
...
31|
32~ } };
|
```
r? `@estebank`
`@rustbot` label +A-diagnostics +A-suggestion-diagnostics
Support lint expectations for `--force-warn` lints (RFC 2383)
Rustc has a `--force-warn` flag, which overrides lint level attributes and forces the diagnostics to always be warn. This means, that for lint expectations, the diagnostic can't be suppressed as usual. This also means that the expectation would not be fulfilled, even if a lint had been triggered in the expected scope.
This PR now also tracks the expectation ID in the `ForceWarn` level. I've also made some minor adjustments, to possibly catch more bugs and make the whole implementation more robust.
This will probably conflict with https://github.com/rust-lang/rust/pull/97718. That PR should ideally be reviewed and merged first. The conflict itself will be trivial to fix.
---
r? `@wesleywiser`
cc: `@flip1995` since you've helped with the initial review and also discussed this topic with me. 🙃
Follow-up of: https://github.com/rust-lang/rust/pull/87835
Issue: https://github.com/rust-lang/rust/issues/85549
Yeah, and that's it.
lint: add diagnostic translation migration lints
Introduce allow-by-default lints for checking whether diagnostics are written in
`SessionDiagnostic` or `AddSubdiagnostic` impls and whether diagnostics are translatable. These lints can be denied for modules once they are fully migrated to impls and translation.
These lints are intended to be temporary - once all diagnostics have been changed then we can just change the APIs we have and that will enforce these constraints thereafter.
r? `````@oli-obk`````
Introduce allow-by-default lints for checking whether diagnostics are
written in `SessionDiagnostic`/`AddSubdiagnostic` impls and whether
diagnostics are translatable. These lints can be denied for modules once
they are fully migrated to impls and translation.
Signed-off-by: David Wood <david.wood@huawei.com>
Fix `delayed_good_path_bug` ice for expected diagnostics (RFC 2383)
Fixes a small ICE with the `delayed_good_path_bug` check.
---
r? ``@wesleywiser``
cc: ``@eddyb`` this might be interesting, since you've added a `FIXME` comment above the modified check which kind of discusses a case like this
closes: https://github.com/rust-lang/rust/issues/95540
cc: https://github.com/rust-lang/rust/issues/85549
To render the message of a Fluent attribute, the identifier of the
Fluent message must be known. `DiagnosticMessage::FluentIdentifier`
contains both the message's identifier and optionally the identifier of
an attribute. Generated constants for each attribute would therefore
need to be named uniquely (amongst all error messages) or be able to
refer to only the attribute identifier which will be combined with a
message identifier later. In this commit, the latter strategy is
implemented as part of the `Diagnostic` type's functions for adding
subdiagnostics of various kinds.
Signed-off-by: David Wood <david.wood@huawei.com>
Adds a new `fluent_messages` macro which performs compile-time
validation of the compiler's Fluent resources (i.e. that the resources
parse and don't multiply define the same messages) and generates
constants that make using those messages in diagnostics more ergonomic.
For example, given the following invocation of the macro..
```ignore (rust)
fluent_messages! {
typeck => "./typeck.ftl",
}
```
..where `typeck.ftl` has the following contents..
```fluent
typeck-field-multiply-specified-in-initializer =
field `{$ident}` specified more than once
.label = used more than once
.label-previous-use = first use of `{$ident}`
```
...then the macro parse the Fluent resource, emitting a diagnostic if it
fails to do so, and will generate the following code:
```ignore (rust)
pub static DEFAULT_LOCALE_RESOURCES: &'static [&'static str] = &[
include_str!("./typeck.ftl"),
];
mod fluent_generated {
mod typeck {
pub const field_multiply_specified_in_initializer: DiagnosticMessage =
DiagnosticMessage::fluent("typeck-field-multiply-specified-in-initializer");
pub const field_multiply_specified_in_initializer_label_previous_use: DiagnosticMessage =
DiagnosticMessage::fluent_attr(
"typeck-field-multiply-specified-in-initializer",
"previous-use-label"
);
}
}
```
When emitting a diagnostic, the generated constants can be used as
follows:
```ignore (rust)
let mut err = sess.struct_span_err(
span,
fluent::typeck::field_multiply_specified_in_initializer
);
err.span_default_label(span);
err.span_label(
previous_use_span,
fluent::typeck::field_multiply_specified_in_initializer_label_previous_use
);
err.emit();
```
Signed-off-by: David Wood <david.wood@huawei.com>
Add a new derive, `#[derive(SessionSubdiagnostic)]`, which enables
deriving structs for labels, notes, helps and suggestions.
Signed-off-by: David Wood <david.wood@huawei.com>
Since Cargo wants to do its own fatal error handling for unused
dependencies, add the option `--json unused-externs-silent` which
has the original behaviour of not indicating non-zero exit status for
`deny`/`forbid`-level unused dependencies.
Remove `--extern-location` and all associated code
`--extern-location` was an experiment to investigate the best way to
generate useful diagnostics for unused dependency warnings by enabling a
build system to identify the corresponding build config.
While I did successfully use this, I've since been convinced the
alternative `--json unused-externs` mechanism is the way to go, and
there's no point in having two mechanisms with basically the same
functionality.
This effectively reverts https://github.com/rust-lang/rust/pull/72603
`--extern-location` was an experiment to investigate the best way to
generate useful diagnostics for unused dependency warnings by enabling a
build system to identify the corresponding build config.
While I did successfully use this, I've since been convinced the
alternative `--json unused-externs` mechanism is the way to go, and
there's no point in having two mechanisms with basically the same
functionality.
This effectively reverts https://github.com/rust-lang/rust/pull/72603
Loading the fallback bundle in compilation sessions that won't go on to
emit any errors unnecessarily degrades compile time performance, so
lazily create the Fluent bundle when it is first required.
Signed-off-by: David Wood <david.wood@huawei.com>
Non-subdiagnostic fields (i.e. those that don't have `#[label]`
attributes or similar and are just additional context) have to be added
as arguments for Fluent messages to refer them. This commit extends the
`SessionDiagnostic` derive to do this for all fields that do not have
attributes and introduces an `IntoDiagnosticArg` trait that is
implemented on all types that can be converted to a argument for Fluent.
Signed-off-by: David Wood <david.wood@huawei.com>
Extend loading of Fluent bundles so that bundles can be loaded from the
sysroot based on the language requested by the user, or using a nightly
flag.
Sysroot bundles are loaded from `$sysroot/share/locale/$locale/*.ftl`.
Signed-off-by: David Wood <david.wood@huawei.com>
This commit updates the signatures of all diagnostic functions to accept
types that can be converted into a `DiagnosticMessage`. This enables
existing diagnostic calls to continue to work as before and Fluent
identifiers to be provided. The `SessionDiagnostic` derive just
generates normal diagnostic calls, so these APIs had to be modified to
accept Fluent identifiers.
In addition, loading of the "fallback" Fluent bundle, which contains the
built-in English messages, has been implemented.
Each diagnostic now has "arguments" which correspond to variables in the
Fluent messages (necessary to render a Fluent message) but no API for
adding arguments has been added yet. Therefore, diagnostics (that do not
require interpolation) can be converted to use Fluent identifiers and
will be output as before.
`MultiSpan` contains labels, which are more complicated with the
introduction of diagnostic translation and will use types from
`rustc_errors` - however, `rustc_errors` depends on `rustc_span` so
`rustc_span` cannot use types like `DiagnosticMessage` without
dependency cycles. Introduce a new `rustc_error_messages` crate that can
contain `DiagnosticMessage` and `MultiSpan`.
Signed-off-by: David Wood <david.wood@huawei.com>
Introduce a `DiagnosticMessage` type that will enable diagnostic
messages to be simple strings or Fluent identifiers.
`DiagnosticMessage` is now used in the implementation of the standard
`DiagnosticBuilder` APIs.
Signed-off-by: David Wood <david.wood@huawei.com>
There are a few places were we have to construct it, though, and a few
places that are more invasive to change. To do this, we create a
constructor with a long obvious name.
Improve `expect` impl and handle `#[expect(unfulfilled_lint_expectations)]` (RFC 2383)
This PR updates unstable `ExpectationIds` in stashed diagnostics and adds some asserts to ensure that the stored expectations are really empty in the end. Additionally, it handles the `#[expect(unfulfilled_lint_expectations)]` case.
According to the [Errors and lints docs](https://rustc-dev-guide.rust-lang.org/diagnostics.html#diagnostic-levels) the `error` level should only be used _"when the compiler detects a problem that makes it unable to compile the program"_. As this isn't the case with `#[expect(unfulfilled_lint_expectations)]` I decided to only create a warning. To avoid adding a new lint only for this case, I simply emit a `unfulfilled_lint_expectations` diagnostic with an additional note.
---
r? `@wesleywiser` I'm requesting a review from you since you reviewed the previous PR https://github.com/rust-lang/rust/pull/87835. You are welcome to reassign it if you're busy 🙃
rfc: [RFC-2383](https://rust-lang.github.io/rfcs/2383-lint-reasons.html)
tracking issue: https://github.com/rust-lang/rust/issues/85549
cc: `@flip1995` In case you're also interested in this :)
This updates the standard library's documentation to use the new syntax. The
documentation is worthwhile to update as it should be more idiomatic
(particularly for features like this, which are nice for users to get acquainted
with). The general codebase is likely more hassle than benefit to update: it'll
hurt git blame, and generally updates can be done by folks updating the code if
(and when) that makes things more readable with the new format.
A few places in the compiler and library code are updated (mostly just due to
already having been done when this commit was first authored).
Implementation of the `expect` attribute (RFC 2383)
This is an implementation of the `expect` attribute as described in [RFC-2383](https://rust-lang.github.io/rfcs/2383-lint-reasons.html). The attribute allows the suppression of lint message by expecting them. Unfulfilled lint expectations (meaning no expected lint was caught) will emit the `unfulfilled_lint_expectations` lint at the `expect` attribute.
### Example
#### input
```rs
// required feature flag
#![feature(lint_reasons)]
#[expect(unused_mut)] // Will warn about an unfulfilled expectation
#[expect(unused_variables)] // Will be fulfilled by x
fn main() {
let x = 0;
}
```
#### output
```txt
warning: this lint expectation is unfulfilled
--> $DIR/trigger_lint.rs:3:1
|
LL | #[expect(unused_mut)] // Will warn about an unfulfilled expectation
| ^^^^^^^^^^
|
= note: `#[warn(unfulfilled_lint_expectations)]` on by default
```
### Implementation
This implementation introduces `Expect` as a new lint level for diagnostics, which have been expected. All lint expectations marked via the `expect` attribute are collected in the [`LintLevelsBuilder`] and assigned an ID that is stored in the new lint level. The `LintLevelsBuilder` stores all found expectations and the data needed to emit the `unfulfilled_lint_expectations` in the [`LintLevelsMap`] which is the result of the [`lint_levels()`] query.
The [`rustc_errors::HandlerInner`] is the central error handler in rustc and handles the emission of all diagnostics. Lint message with the level `Expect` are suppressed during this emission, while the expectation ID is stored in a set which marks them as fulfilled. The last step is then so simply check if all expectations collected by the [`LintLevelsBuilder`] in the [`LintLevelsMap`] have been marked as fulfilled in the [`rustc_errors::HandlerInner`]. Otherwise, a new lint message will be emitted.
The implementation of the `LintExpectationId` required some special handling to make it stable between sessions. Lints can be emitted during [`EarlyLintPass`]es. At this stage, it's not possible to create a stable identifier. The level instead stores an unstable identifier, which is later converted to a stable `LintExpectationId`.
### Followup TO-DOs
All open TO-DOs have been marked with `FIXME` comments in the code. This is the combined list of them:
* [ ] The current implementation doesn't cover cases where the `unfulfilled_lint_expectations` lint is actually expected by another `expect` attribute.
* This should be easily possible, but I wanted to get some feedback before putting more work into this.
* This could also be done in a new PR to not add to much more code to this one
* [ ] Update unstable documentation to reflect this change.
* [ ] Update unstable expectation ids in [`HandlerInner::stashed_diagnostics`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_errors/struct.HandlerInner.html#structfield.stashed_diagnostics)
### Open questions
I also have a few open questions where I would like to get feedback on:
1. The RFC discussion included a suggestion to change the `expect` attribute to something else. (Initiated by `@Ixrec` [here](https://github.com/rust-lang/rfcs/pull/2383#issuecomment-378424091), suggestion from `@scottmcm` to use `#[should_lint(...)]` [here](https://github.com/rust-lang/rfcs/pull/2383#issuecomment-378648877)). No real conclusion was drawn on that point from my understanding. Is this still open for discussion, or was this discarded with the merge of the RFC?
2. How should the expect attribute deal with the new `force-warn` lint level?
---
This approach was inspired by a discussion with `@LeSeulArtichaut.`
RFC tracking issue: #54503
Mentoring/Implementation issue: #85549
[`LintLevelsBuilder`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/levels/struct.LintLevelsBuilder.html
[`LintLevelsMap`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/lint/struct.LintLevelMap.html
[`lint_levels()`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/context/struct.TyCtxt.html#method.lint_levels
[`rustc_errors::HandlerInner`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_errors/struct.HandlerInner.html
[`EarlyLintPass`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/trait.EarlyLintPass.html
`Decoder` has two impls:
- opaque: this impl is already partly infallible, i.e. in some places it
currently panics on failure (e.g. if the input is too short, or on a
bad `Result` discriminant), and in some places it returns an error
(e.g. on a bad `Option` discriminant). The number of places where
either happens is surprisingly small, just because the binary
representation has very little redundancy and a lot of input reading
can occur even on malformed data.
- json: this impl is fully fallible, but it's only used (a) for the
`.rlink` file production, and there's a `FIXME` comment suggesting it
should change to a binary format, and (b) in a few tests in
non-fundamental ways. Indeed #85993 is open to remove it entirely.
And the top-level places in the compiler that call into decoding just
abort on error anyway. So the fallibility is providing little value, and
getting rid of it leads to some non-trivial performance improvements.
Much of this commit is pretty boring and mechanical. Some notes about
a few interesting parts:
- The commit removes `Decoder::{Error,error}`.
- `InternIteratorElement::intern_with`: the impl for `T` now has the same
optimization for small counts that the impl for `Result<T, E>` has,
because it's now much hotter.
- Decodable impls for SmallVec, LinkedList, VecDeque now all use
`collect`, which is nice; the one for `Vec` uses unsafe code, because
that gave better perf on some benchmarks.
This was a regression from https://github.com/rust-lang/rust/pull/87337;
the `panic_if_treat_err_as_bug` function only checked the number of hard
errors, not the number of lint errors.
The only reason to use `abort_if_errors` is when the program is so broken that either:
1. later passes get confused and ICE
2. any diagnostics from later passes would be noise
This is never the case for lints, because the compiler has to be able to deal with `allow`-ed lints.
So it can continue to lint and compile even if there are lint errors.
