Summary
pkg/linters/tolowerequalfold is a CI-enforced linter, but its package-identity check matches the strings package by the syntactic identifier name rather than by type information. This is the same syntactic_stdlib_match antipattern already migrated to astutil.IsPkgSelector in sortslice (#38029), rawloginlib (#39981), and regexpcompileinfunction (#39733), and currently tracked for the CI-enforced trio in #40243 (osexitinlibrary / fprintlnsprintf / errstringmatch).
tolowerequalfold was missed by the #40243 sweep — it is a distinct, additional CI-enforced holdout.
Location
pkg/linters/tolowerequalfold/tolowerequalfold.go:255 (in caseConvArg):
ident, ok := sel.X.(*ast.Ident)
if !ok {
return nil, false
}
if ident.Name != "strings" { // <-- syntactic name match, no TypesInfo
return nil, false
}
if sel.Sel.Name != "ToLower" && sel.Sel.Name != "ToUpper" {
return nil, false
}Both detection paths funnel through this function: isCaseConvCall (line 212) delegates directly to caseConvArg, so line 255 is the single chokepoint for the whole analyzer.
Why this is wrong
- False positive (shadowing): a local variable, parameter, or field named
strings whose type has ToLower/ToUpper methods is falsely flagged as the stdlib strings package.
- False negative (alias import):
import str "strings" → str.ToLower(x) escapes detection entirely.
The linter already has full type information available and uses it correctly elsewhere — sameOperand at line 271 calls pass.TypesInfo.ObjectOf. Only the package-identity check was left syntactic.
Recommendation
Replace the manual *ast.Ident extraction + ident.Name != "strings" check (lines 251–257) with the canonical helper, which is already imported (pkg/linters/internal/astutil, line 15):
sel, ok := call.Fun.(*ast.SelectorExpr)
if !ok {
return nil, false
}
if !astutil.IsPkgSelector(pass, sel, "strings") {
return nil, false
}
if sel.Sel.Name != "ToLower" && sel.Sel.Name != "ToUpper" {
return nil, false
}Impact / current state
Latent: a repo-wide grep shows no aliased strings import and no shadowing strings variable in production today, so there is no live miss right now. The fix is a consistency / future-proofing change that aligns the last CI-enforced holdout with the team's active migration, preventing a silent build pass/fail divergence the moment such code is introduced.
Validation checklist
Effort
Small — single-file, ~6 lines, helper already imported, existing test scaffold.
Not a duplicate of #40243 (which enumerates osexitinlibrary, fprintlnsprintf, errstringmatch) or #40435 (fileclosenotdeferred, contextcancelnotdeferred). tolowerequalfold is a separate CI-enforced analyzer.
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Summary
pkg/linters/tolowerequalfoldis a CI-enforced linter, but its package-identity check matches thestringspackage by the syntactic identifier name rather than by type information. This is the samesyntactic_stdlib_matchantipattern already migrated toastutil.IsPkgSelectorinsortslice(#38029),rawloginlib(#39981), andregexpcompileinfunction(#39733), and currently tracked for the CI-enforced trio in #40243 (osexitinlibrary / fprintlnsprintf / errstringmatch).tolowerequalfoldwas missed by the #40243 sweep — it is a distinct, additional CI-enforced holdout.Location
pkg/linters/tolowerequalfold/tolowerequalfold.go:255(incaseConvArg):Both detection paths funnel through this function:
isCaseConvCall(line 212) delegates directly tocaseConvArg, so line 255 is the single chokepoint for the whole analyzer.Why this is wrong
stringswhose type hasToLower/ToUppermethods is falsely flagged as the stdlibstringspackage.import str "strings"→str.ToLower(x)escapes detection entirely.The linter already has full type information available and uses it correctly elsewhere —
sameOperandat line 271 callspass.TypesInfo.ObjectOf. Only the package-identity check was left syntactic.Recommendation
Replace the manual
*ast.Identextraction +ident.Name != "strings"check (lines 251–257) with the canonical helper, which is already imported (pkg/linters/internal/astutil, line 15):Impact / current state
Latent: a repo-wide grep shows no aliased
stringsimport and no shadowingstringsvariable in production today, so there is no live miss right now. The fix is a consistency / future-proofing change that aligns the last CI-enforced holdout with the team's active migration, preventing a silent build pass/fail divergence the moment such code is introduced.Validation checklist
import str "strings"; str.ToLower(a) == str.ToLower(b)→ expect diagnostic (FN fix).stringsvalue type exposingToLower→ expect no diagnostic (FP fix).go test ./pkg/linters/tolowerequalfold/...).pkg/lintersforName (==|!=) "strings"→ only intended sites remain.Effort
Small — single-file, ~6 lines, helper already imported, existing test scaffold.
Not a duplicate of #40243 (which enumerates osexitinlibrary, fprintlnsprintf, errstringmatch) or #40435 (fileclosenotdeferred, contextcancelnotdeferred).
tolowerequalfoldis a separate CI-enforced analyzer.