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sortslice: match stdlib sort calls by type identity, not identifier text #38053

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Merged
pelikhan merged 5 commits into from
Jun 9, 2026
+38 −1
Merged

sortslice: match stdlib sort calls by type identity, not identifier text #38053

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cbcd509
Initial plan
Copilot Jun 9, 2026
2c43a51
Fix sortslice to match stdlib sort by package identity
Copilot Jun 9, 2026
135db56
Guard sortslice package-object lookup against nil types info
Copilot Jun 9, 2026
669902f
Document nil types-info guard in sortslice analyzer
Copilot Jun 9, 2026
43099fe
Add TypesInfo nil guard in sortslice analyzer
Copilot Jun 9, 2026
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16 changes: 15 additions & 1 deletion pkg/linters/sortslice/sortslice.go
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ package sortslice
import (
"fmt"
"go/ast"
"go/types"

"golang.org/x/tools/go/analysis"
"golang.org/x/tools/go/analysis/passes/inspect"
Expand Down Expand Up @@ -52,12 +53,25 @@ func run(pass *analysis.Pass) (any, error) {
return
}
pkgIdent, ok := sel.X.(*ast.Ident)
if !ok || pkgIdent.Name != "sort" {
if !ok {
return
}
if pass.TypesInfo == nil {
return
}
obj := pass.TypesInfo.ObjectOf(pkgIdent)

@github-actions github-actions Bot Jun 9, 2026

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Missing nil guard on pass.TypesInfo itself: the code calls pass.TypesInfo.ObjectOf(...) without first checking pass.TypesInfo != nil, so a non-standard or embedded driver that omits type info would panic here rather than skip gracefully.

💡 Suggested fix

Add an early guard before the ObjectOf call:

if pass.TypesInfo == nil {
    return
}
obj := pass.TypesInfo.ObjectOf(pkgIdent)

The existing if obj == nil check (line 61) only protects against ObjectOf returning nil on an initialised TypesInfo — it does not prevent a nil-pointer dereference on pass.TypesInfo itself. Standard drivers (go vet, golangci-lint, analysistest) always populate TypesInfo, so this will not trigger in normal CI; but it is a latent panic for any embedded or custom driver that skips type-checking. Adding the guard is a one-liner and is consistent with the defensive style already present in this function.

// ObjectOf can be nil when type information is incomplete.
if obj == nil {
return
}
pkgName, ok := obj.(*types.PkgName)
if !ok || pkgName.Imported().Path() != "sort" {

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[/tdd] The ReportRangef calls a few lines below use hardcoded "sort.Slice" / "sort.SliceStable" strings, so aliased-import users see sort.Slice is not type-safe for code that says s.Slice(...). The alias_import.go testdata validates this as intentional. If so, a short comment in the switch block explaining the design choice would protect future contributors from accidentally "fixing" it to the local alias name.

💡 Alternative: dynamic message using the local alias

If you prefer the message to match the user's actual code:

case "Slice":
    pass.ReportRangef(call, "%s.Slice is not type-safe; use slices.SortFunc instead", pkgIdent.Name)
case "SliceStable":
    pass.ReportRangef(call, "%s.SliceStable is not type-safe; use slices.SortStableFunc instead", pkgIdent.Name)

With import s "sort" the diagnostic would then read s.Slice is not type-safe, which maps directly to the code the user wrote. The alias_import.go // want annotations would need updating accordingly.

return
}

switch sel.Sel.Name {
case "Slice":
// Keep diagnostics on canonical stdlib names even for aliased imports.
pass.ReportRangef(call, "sort.Slice is not type-safe; use slices.SortFunc instead")
case "SliceStable":
pass.ReportRangef(call, "sort.SliceStable is not type-safe; use slices.SortStableFunc instead")
Expand Down
11 changes: 11 additions & 0 deletions pkg/linters/sortslice/testdata/src/sortslice/alias_import.go
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@@ -0,0 +1,11 @@
package sortslice

import s "sort"

func BadSliceAliasedImport(items []string) {
s.Slice(items, func(i, j int) bool { return items[i] < items[j] }) // want `sort\.Slice is not type-safe`

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[/diagnose] The // want annotation documents that the expected diagnostic text is sort\.Slice even though the call is s.Slice. This is a useful precision signal: when type-info resolution was added, the message string was intentionally left as the canonical package name rather than the local alias. A short comment here (or at the switch in sortslice.go) would make this boundary explicit and prevent a future refactor from "fixing" the message to s.Slice and breaking this expectation.

}

func BadSliceStableAliasedImport(items []string) {
s.SliceStable(items, func(i, j int) bool { return items[i] < items[j] }) // want `sort\.SliceStable is not type-safe`
}
12 changes: 12 additions & 0 deletions pkg/linters/sortslice/testdata/src/sortslice/shadowed_identifier.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
package sortslice

type customSort struct{}

func (customSort) Slice(_ []string, _ func(i, j int) bool) {}
func (customSort) SliceStable(_ []string, _ func(i, j int) bool) {}

func GoodShadowedSortIdentifier(items []string) {
sort := customSort{}
sort.Slice(items, func(i, j int) bool { return items[i] < items[j] })
sort.SliceStable(items, func(i, j int) bool { return items[i] < items[j] })
}
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