Add linter wastedassign (#1651)

test/testdata/wastedassign.go

@@ -0,0 +1,107 @@
+//args: -Ewastedassign
+package testdata
+
+import (
+	"strings"
+)
+
+func p(x int) int {
+	return x + 1
+}
+
+func typeSwitchNoError(val interface{}, times uint) interface{} {
+	switch hoge := val.(type) {
+	case int:
+		return 12
+	case string:
+		return strings.Repeat(hoge, int(times))
+	default:
+		return nil
+	}
+}
+
+func noUseParamsNoError(params string) int {
+	a := 12
+	println(a)
+	return a
+}
+
+func manyif(param int) int {
+	println(param)
+	useOutOfIf := 1212121 // ERROR "wasted assignment"
+	ret := 0
+	if false {
+		useOutOfIf = 200 // ERROR "reassigned, but never used afterwards"
+		return 0
+	} else if param == 100 {
+		useOutOfIf = 100 // ERROR "wasted assignment"
+		useOutOfIf = 201
+		useOutOfIf = p(useOutOfIf)
+		useOutOfIf += 200 // ERROR "wasted assignment"
+	} else {
+		useOutOfIf = 100
+		useOutOfIf += 100
+		useOutOfIf = p(useOutOfIf)
+		useOutOfIf += 200 // ERROR "wasted assignment"
+	}
+
+	if false {
+		useOutOfIf = 200 // ERROR "reassigned, but never used afterwards"
+		return 0
+	} else if param == 200 {
+		useOutOfIf = 100 // ERROR "wasted assignment"
+		useOutOfIf = 201
+		useOutOfIf = p(useOutOfIf)
+		useOutOfIf += 200
+	} else {
+		useOutOfIf = 100
+		useOutOfIf += 100
+		useOutOfIf = p(useOutOfIf)
+		useOutOfIf += 200
+	}
+	println(useOutOfIf)
+	useOutOfIf = 192
+	useOutOfIf += 100
+	useOutOfIf += 200 // ERROR "reassigned, but never used afterwards"
+	return ret
+}
+
+func checkLoopTest() int {
+	hoge := 12
+	noUse := 1111
+	println(noUse)
+
+	noUse = 1111 // ERROR "reassigned, but never used afterwards"
+	for {
+		if hoge == 14 {
+			break
+		}
+		hoge = hoge + 1
+	}
+	return hoge
+}
+
+func infinity() {
+	var i int
+	var hoge int
+	for {
+		hoge = 5 // ERROR "reassigned, but never used afterwards"
+	}
+
+	println(i)
+	println(hoge)
+	return
+}
+
+func infinity2() {
+	var i int
+	var hoge int
+	for {
+		hoge = 5
+		break
+	}
+
+	println(i)
+	println(hoge)
+	return
+}