Add staticcheck tool

vendor/honnef.co/go/tools/simple/s1031/s1031.go

@@ -0,0 +1,71 @@
+package s1031
+
+import (
+	"go/types"
+
+	"honnef.co/go/tools/analysis/code"
+	"honnef.co/go/tools/analysis/facts/generated"
+	"honnef.co/go/tools/analysis/lint"
+	"honnef.co/go/tools/analysis/report"
+	"honnef.co/go/tools/go/types/typeutil"
+	"honnef.co/go/tools/pattern"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
+	Analyzer: &analysis.Analyzer{
+		Name:     "S1031",
+		Run:      run,
+		Requires: append([]*analysis.Analyzer{generated.Analyzer}, code.RequiredAnalyzers...),
+	},
+	Doc: &lint.RawDocumentation{
+		Title: `Omit redundant nil check around loop`,
+		Text: `You can use range on nil slices and maps, the loop will simply never
+execute. This makes an additional nil check around the loop
+unnecessary.`,
+		Before: `
+if s != nil {
+    for _, x := range s {
+        ...
+    }
+}`,
+		After: `
+for _, x := range s {
+    ...
+}`,
+		Since: "2017.1",
+		// MergeIfAll because x might be a channel under some build tags.
+		// you shouldn't write code like that…
+		MergeIf: lint.MergeIfAll,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+var checkNilCheckAroundRangeQ = pattern.MustParse(`
+	(IfStmt
+		nil
+		(BinaryExpr x@(Object _) "!=" (Builtin "nil"))
+		[(RangeStmt _ _ _ x _)]
+		nil)`)
+
+func run(pass *analysis.Pass) (any, error) {
+	for node, m := range code.Matches(pass, checkNilCheckAroundRangeQ) {
+		ok := typeutil.All(m.State["x"].(types.Object).Type(), func(term *types.Term) bool {
+			switch term.Type().Underlying().(type) {
+			case *types.Slice, *types.Map:
+				return true
+			case *types.TypeParam, *types.Chan, *types.Pointer, *types.Signature:
+				return false
+			default:
+				lint.ExhaustiveTypeSwitch(term.Type().Underlying())
+				return false
+			}
+		})
+		if ok {
+			report.Report(pass, node, "unnecessary nil check around range", report.ShortRange(), report.FilterGenerated())
+		}
+	}
+	return nil, nil
+}