feat(lint): W018 — e.kind compared against an out-of-set error kind (#469)#525
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| obj->data.ident.name, (op[0] == '=' ? "==" : op), lit, sugg); | ||
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| static void w018_scan(ASTNode *n, LintContext *ctx, W018Scope *sc) { |
…469) A catch handler comparing a caught error's `.kind` against a string that is a near-miss of a real kind — a case variant ("IO"), a single-character typo ("index_rage"), or a kind renamed out from under the handler — is dead code that silently never fires. W018 warns and suggests the intended kind (the silent-tolerance class the lint train fences). Zero-false-positive by construction, three gates: 1. the `.kind` must be read off a CATCH-BOUND variable (tracked through the walk via trycatch.err_name), so `.kind` on an unrelated user dict never fires; 2. an exactly-valid kind is silent; 3. only a near-miss fires — a case variant, or a bounded-Levenshtein edit distance of 1 — so a genuinely custom `throw {kind: "..."}` value, many edits from every builtin, stays silent. The closed kind set is derived from err_kind_name(EK_INTERNAL..EK_USER) at run time — no hand list to drift, and it already covers the post-#509 `deadlock` kind (verified: a valid `deadlock` comparison stays silent). Runs inside the shared lint_run_checks, so it also flows to the LSP. Calibrated to ZERO hits over lib/, the test corpus, examples/, and the consumer repos (ouroboros/liferaft/tidelog/DMG/Tidepool). Regression: tests/test_lint.sh — fires on index_rage (+ suggests index_range) and the IO case variant; silent on valid kinds incl. deadlock, a far-off custom kind, and .kind off a non-catch var. Full suite green release + ASan (leaks on), 2700/2700, no leak-tally increase. Closes #469 Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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What
A
catchhandler comparing a caught error's.kindagainst a string that is a near-miss of a real kind — a case variant ("IO"), a single-character typo ("index_rage"), or a kind renamed out from under the handler — is dead code that silently never fires.W018warns and suggests the intended kind — the silent-tolerance class the lint train exists to fence.Zero-false-positive by construction
Three gates, all required to fire:
.kindis read off a catch-bound variable (tracked through the walk viatrycatch.err_name) —.kindon an unrelated user dict never fires;throw {kind: "..."}value, many edits from every builtin, stays silent.The closed kind set is derived from
err_kind_name(EK_INTERNAL..EK_USER)at run time — no hand list to drift when a kind is added, and it already covers the post-#509deadlock(verified: a validdeadlockcomparison stays silent). The check lives in the sharedlint_run_checks, so it also flows to the LSP.Calibration: zero hits over
lib/, the test corpus,examples/, and the consumer repos (ouroboros/liferaft/tidelog/DMG/Tidepool).Verification
tests/test_lint.sh(6 new cases): fires onindex_rage(+ suggestsindex_range) and theIOcase variant; silent on valid kinds incl.deadlock, a far-off custom kind, and.kindoff a non-catch var.detect_leaks=1): 2700/2700, 0 failed, no leak-tally increase.Docs
docs/DIAGNOSTICS.md:W018row in the W-code table.CHANGELOG.md: entry under[Unreleased] → Added.Closes #469
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