Tracking Issue for `LintDiagnostic` migration

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#153,099 opened on Feb 25, 2026 6 comments 0 reactions 2 assignees View on GitHub

@GuillaumeGomez is already working on this.

Since Feb 25, 2026.

A-lints C-tracking-issue

Dominant language: Rust
Stars: 119k
Forks: 16.1k
PR merge metrics: PR metrics pending

Description

This is a tracking issue for the LintDiagnostic migration that @GuillaumeGomez and I are doing.
Mostly meant to be a place we can put ideas and keep track of what is left to do.

Implementation history

Removing `BuiltinLintDiag`

Removing `AttributeLintKind`

Cleanup

TODO list

See if we can remove the span argument from opt_span_diag_lint https://github.com/rust-lang/rust/pull/153091#discussion_r2854619230
- Possible but because of lint_level, we will need to update Diagnostic::into_diag so that it looks like:
```
fn into_diag<F: FnOnce(Span) -> bool>(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Option<Diag<'a, G>>
```
  That will allow to return early on and in particular skip Ty translation into diagnostic message, which would call DiagCtxt::set_must_produce_diag, forcing the Diag to be emitted. So before it's even possible, we need to ensure that the Diag will actually be emitted, and if not, we return early with None.
See if we can get rid of BuiltinLintDiag in favour of a boxed diagnostic of some kind
See if we can undo the perf regression in decorate_builtin_lint, maybe by using boxed diagnostics everywhere

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