Add staticcheck tool

vendor/honnef.co/go/tools/staticcheck/sa4030/sa4030.go

@@ -0,0 +1,70 @@
+package sa4030
+
+import (
+	"fmt"
+
+	"honnef.co/go/tools/analysis/code"
+	"honnef.co/go/tools/analysis/lint"
+	"honnef.co/go/tools/analysis/report"
+	"honnef.co/go/tools/pattern"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
+	Analyzer: &analysis.Analyzer{
+		Name:     "SA4030",
+		Run:      run,
+		Requires: code.RequiredAnalyzers,
+	},
+	Doc: &lint.RawDocumentation{
+		Title: "Ineffective attempt at generating random number",
+		Text: `
+Functions in the \'math/rand\' package that accept upper limits, such
+as \'Intn\', generate random numbers in the half-open interval [0,n). In
+other words, the generated numbers will be \'>= 0\' and \'< n\' – they
+don't include \'n\'. \'rand.Intn(1)\' therefore doesn't generate \'0\'
+or \'1\', it always generates \'0\'.`,
+		Since:    "2022.1",
+		Severity: lint.SeverityWarning,
+		MergeIf:  lint.MergeIfAny,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+var ineffectiveRandIntQ = pattern.MustParse(`
+	(CallExpr
+		(Symbol
+			name@(Or
+				"math/rand.Int31n"
+				"math/rand.Int63n"
+				"math/rand.Intn"
+				"(*math/rand.Rand).Int31n"
+				"(*math/rand.Rand).Int63n"
+				"(*math/rand.Rand).Intn"
+
+				"math/rand/v2.Int32N"
+				"math/rand/v2.Int64N"
+				"math/rand/v2.IntN"
+				"math/rand/v2.N"
+				"math/rand/v2.Uint32N"
+				"math/rand/v2.Uint64N"
+				"math/rand/v2.UintN"
+
+				"(*math/rand/v2.Rand).Int32N"
+				"(*math/rand/v2.Rand).Int64N"
+				"(*math/rand/v2.Rand).IntN"
+				"(*math/rand/v2.Rand).Uint32N"
+				"(*math/rand/v2.Rand).Uint64N"
+				"(*math/rand/v2.Rand).UintN"))
+		[(IntegerLiteral "1")])`)
+
+func run(pass *analysis.Pass) (any, error) {
+	for node, m := range code.Matches(pass, ineffectiveRandIntQ) {
+		report.Report(pass, node,
+			fmt.Sprintf("%s(n) generates a random value 0 <= x < n; that is, the generated values don't include n; %s therefore always returns 0",
+				m.State["name"], report.Render(pass, node)))
+	}
+	return nil, nil
+}