fix: Emit diagnostic for rest array patterns without fixed-length arrays#22424
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lnicola merged 1 commit intoMay 23, 2026
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Add a new inference diagnostic for rest array patterns on arrays whose length is not known to be fixed, plumb it through hir and ide-diagnostics, and add handler tests. AI-assisted: Changes were prepared with GitHub Copilot (GPT-5.3-Codex), then reviewed and validated with local tests.
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Emit a diagnostic when pattern-matching on arrays without a fixed length. This adds an
InferenceDiagnostic::ArrayPatternWithoutFixedLength, converts it into a hir-level diagnostic, and renders it in ide-diagnostics.Why
The codebase contains a FIXME in
crates/hir-ty/src/infer/pat.rsdescribing this missingdiagnostic. Producing a user-facing error clarifies the analyzer's behavior and prevents
surprising inference results.
Refs: rust-analyzer issue #22140
How
ArrayPatternWithoutFixedLengthtocrates/hir-ty/src/infer.rs.crates/hir-ty/src/infer/pat.rs.AnyDiagnosticincrates/hir/src/diagnostics.rs.crates/ide-diagnostics/src/handlers/array_pattern_without_fixed_length.rsand registered it incrates/ide-diagnostics/src/lib.rs.crates/ide-diagnosticscovering both non-fixed-length (error) and fixed-length (no error) cases.Notes for reviewers
CONTRIBUTING.md.