checkers: add new checker stringsCompare

checkers/rules/rules.go

@@ -736,3 +736,34 @@ func dynamicFmtString(m dsl.Matcher) {
 		Suggest("errors.New($f($*args))").
 		Report(`use errors.New($f($*args)) or fmt.Errorf("%s", $f($*args)) instead`)
 }
+
+//doc:summary Detects strings.Compare usage
+//doc:tags    performance experimental
+//doc:before  strings.Compare(x, y)
+//doc:after   x < y
+func stringsCompare(m dsl.Matcher) {
+	m.Match(`strings.Compare($s1, $s2) == 0`).
+		Report(`don't use strings.Compare on hot path, change it to built-in operators`).
+		Suggest(`$s1 == $s2`).
+		At(m["s1"])
+
+	m.Match(`strings.Compare($s1, $s2) < 0`,
+		`strings.Compare($s1, $s2) == -1`).
+		Report(`don't use strings.Compare on hot path, change it to built-in operators`).
+		Suggest(`$s1 < $s2`).
+		At(m["s1"])
+
+	m.Match(`strings.Compare($s1, $s2) > 0`,
+		`strings.Compare($s1, $s2) == 1`).
+		Report(`don't use strings.Compare on hot path, change it to built-in operators`).
+		Suggest(`$s1 > $s2`).
+		At(m["s1"])
+
+	m.Match(`$_ = strings.Compare($s1, $_)`,
+		`$_ := strings.Compare($s1, $_)`,
+		`var $_ = strings.Compare($s1, $_)`,
+		`var $_ $_ = strings.Compare($s1, $_)`,
+		`switch strings.Compare($s1, $_) { $*_ }`).
+		Report(`don't use strings.Compare on hot path, change it to built-in operators`).
+		At(m["s1"])
+}

checkers/testdata/stringsCompare/negative_tests.go

@@ -0,0 +1,21 @@
+package checker_test
+
+import (
+	"bytes"
+)
+
+type s []string
+
+func (s) Compare(x, y string) int {
+	if x < y {
+		return 1
+	}
+	return 0
+}
+
+func negative() {
+	bytes.Compare([]byte{}, []byte{})
+
+	strings := s{}
+	_ = strings.Compare("1", "3") == 0
+}

checkers/testdata/stringsCompare/positive_tests.go

@@ -0,0 +1,36 @@
+package checker_test
+
+import (
+	"strings"
+)
+
+func foo() {
+	f, b := "aaa", "bbb"
+
+	/*! don't use strings.Compare on hot path, change it to built-in operators */
+	if strings.Compare(f, b) == 0 {
+	}
+
+	/*! don't use strings.Compare on hot path, change it to built-in operators */
+	switch strings.Compare(f, b) {
+	case 0:
+		print(0)
+	case 1:
+		print(1)
+	case -1:
+		print(-1)
+	}
+
+	/*! don't use strings.Compare on hot path, change it to built-in operators */
+	switch dd := strings.Compare(f, b); dd {
+	case 0:
+		print(0)
+	case 1:
+		print(1)
+	case -1:
+		print(-1)
+	}
+
+	/*! don't use strings.Compare on hot path, change it to built-in operators */
+	_ = strings.Compare("s", "ww")
+}