Add staticcheck tool

vendor/honnef.co/go/tools/staticcheck/sa1024/sa1024.go

@@ -0,0 +1,75 @@
+package sa1024
+
+import (
+	"go/constant"
+	"sort"
+
+	"honnef.co/go/tools/analysis/callcheck"
+	"honnef.co/go/tools/analysis/lint"
+	"honnef.co/go/tools/internal/passes/buildir"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
+	Analyzer: &analysis.Analyzer{
+		Name:     "SA1024",
+		Requires: []*analysis.Analyzer{buildir.Analyzer},
+		Run:      callcheck.Analyzer(rules),
+	},
+	Doc: &lint.RawDocumentation{
+		Title: `A string cutset contains duplicate characters`,
+		Text: `The \'strings.TrimLeft\' and \'strings.TrimRight\' functions take cutsets, not
+prefixes. A cutset is treated as a set of characters to remove from a
+string. For example,
+
+    strings.TrimLeft("42133word", "1234")
+
+will result in the string \'"word"\' – any characters that are 1, 2, 3 or
+4 are cut from the left of the string.
+
+In order to remove one string from another, use \'strings.TrimPrefix\' instead.`,
+		Since:    "2017.1",
+		Severity: lint.SeverityWarning,
+		MergeIf:  lint.MergeIfAny,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+var rules = map[string]callcheck.Check{
+	"strings.Trim":      check,
+	"strings.TrimLeft":  check,
+	"strings.TrimRight": check,
+}
+
+func check(call *callcheck.Call) {
+	arg := call.Args[1]
+	if !isUniqueStringCutset(arg.Value) {
+		const MsgNonUniqueCutset = "cutset contains duplicate characters"
+		arg.Invalid(MsgNonUniqueCutset)
+	}
+}
+
+func isUniqueStringCutset(v callcheck.Value) bool {
+	if c := callcheck.ExtractConstExpectKind(v, constant.String); c != nil {
+		s := constant.StringVal(c.Value)
+		rs := runeSlice(s)
+		if len(rs) < 2 {
+			return true
+		}
+		sort.Sort(rs)
+		for i, r := range rs[1:] {
+			if rs[i] == r {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+type runeSlice []rune
+
+func (rs runeSlice) Len() int               { return len(rs) }
+func (rs runeSlice) Less(i int, j int) bool { return rs[i] < rs[j] }
+func (rs runeSlice) Swap(i int, j int)      { rs[i], rs[j] = rs[j], rs[i] }