Autofix verification-parity gap: 3 of 9 SuggestedFix linters (stringsindexcontains, sprintfint, stringreplaceminusone) have zero [Content truncated due to length]

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Summary

9 custom analyzers emit analysis.SuggestedFix text edits (batch-applied under -fix), but only 6 verify the emitted fix output via analysistest.RunWithSuggestedFixes + a .golden file. 3 emit fixes whose generated source is never checked by any test:

Linter	Emits SuggestedFix	Fix builder	Test entrypoint	.golden?
stringsindexcontains (new, R56 registry 40→41)	yes	buildContainsFix (stringsindexcontains.go:226-242)	analysistest.Run (stringsindexcontains_test.go:15)	none
sprintfint	yes	buildItoaFix (sprintfint.go:94-107)	analysistest.Run (sprintfint_test.go:16)	none
stringreplaceminusone	yes	buildReplaceAllFix (stringreplaceminusone.go:96-116)	analysistest.Run (stringreplaceminusone_test.go:15)	none

The 6 that DO verify: ctxbackground, execcommandwithoutcontext, fprintlnsprintf, lenstringsplit, lenstringzero, tolowerequalfold (8 .golden files total under pkg/linters/).

Why this matters

analysistest.Run only checks diagnostic positions/messages (the // want comments). It never applies the TextEdits, so the reconstructed replacement string is completely unexercised. For an autofix linter that is -fix-applied in batch, a defect in the fix builder ships silently — the diagnostic still lands on the right line, but the rewritten code is wrong.

This is not hypothetical: R55 found a real semantic-change bug in a fix builder (fprintlnsprintf buildFprintfFix dropped a trailing newline). That linter did have golden coverage, which is how such regressions are meant to be caught. The 3 linters above have no such safety net, so any future edit to their fix builders (or a latent defect today) would not be detected.

Concrete latent-risk examples in the uncovered set:

• sprintfint documents in its own Analyzer.Doc that fixes "may require goimports to add/remove imports" — the strconv.Itoa(...) rewrite (sprintfint.go:105) leaves strconv unimported / fmt possibly unused. Import-management behavior is precisely the kind of thing a golden file pins.
• stringsindexcontains reconstructs the replacement from astutil.NodeText (go/printer reprint of the arg AST, astutil.go:117), e.g. "!" + pkg + ".Contains(" + sText + ", " + subText + ")" (stringsindexcontains.go:229). The reprinted-arg + negation path is untested.

(Note: I audited stringsindexcontains's detection and fix logic and both are semantically correct today — all 6 comparison forms + yoda variants map correctly to strings.Contains/!strings.Contains, args preserved in call order. This issue is about the missing verification harness, not a known miscompile.)

Evidence

Grep reconciliation

# emit SuggestedFix (non-test):
pkg/linters/{ctxbackground,execcommandwithoutcontext,fprintlnsprintf,lenstringsplit,
            lenstringzero,sprintfint,stringreplaceminusone,stringsindexcontains,
            tolowerequalfold}/*.go   → 9 linters

# use RunWithSuggestedFixes (test):
pkg/linters/{ctxbackground,execcommandwithoutcontext,fprintlnsprintf,lenstringsplit,
            lenstringzero,tolowerequalfold}/*_test.go   → 6 linters

# *.golden under pkg/linters/ → 8 files (all belong to the 6 verified linters)
# stringsindexcontains / sprintfint / stringreplaceminusone → 0 golden, analysistest.Run only

Recommended fix (uniform, per linter)

For each of the 3 linters:

1. Add a testdata/src/<name>/<name>.go.golden capturing the expected post-fix source for each // want case (contains + negated + yoda variants; for sprintfint, the strconv.Itoa rewrite).
2. Switch the test from analysistest.Run(...) to analysistest.RunWithSuggestedFixes(t, testdata, <pkg>.Analyzer, "<name>") — matching the pattern already used by fprintlnsprintf_test.go, lenstringzero_test.go, etc.

Validation checklist

• go test ./pkg/linters/stringsindexcontains/... ./pkg/linters/sprintfint/... ./pkg/linters/stringreplaceminusone/... passes with RunWithSuggestedFixes.
• Each .golden reflects the exact reprinted replacement (verify sprintfint golden documents the import-management caveat, or gate the linter out of -fix batches until goimports is wired).
• All 9 SuggestedFix linters now covered → grep parity: RunWithSuggestedFixes count == SuggestedFix-emitting count.

Effort: small–medium (test-only; 3 golden files + 3 one-line test swaps). No production analyzer changes required.

References: run §28695406176

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