Add linter wastedassign (#1651)

go.mod

@@ -54,6 +54,7 @@ require (
 	github.com/polyfloyd/go-errorlint v0.0.0-20201127212506-19bd8db6546f
 	github.com/ryancurrah/gomodguard v1.2.0
 	github.com/ryanrolds/sqlclosecheck v0.3.0
+	github.com/sanposhiho/wastedassign v0.1.3
 	github.com/securego/gosec/v2 v2.6.1
 	github.com/shazow/go-diff v0.0.0-20160112020656-b6b7b6733b8c
 	github.com/shirou/gopsutil/v3 v3.21.1

go.sum

@@ -353,6 +353,8 @@ github.com/ryancurrah/gomodguard v1.2.0/go.mod h1:rNqbC4TOIdUDcVMSIpNNAzTbzXAZa6
 github.com/ryanrolds/sqlclosecheck v0.3.0 h1:AZx+Bixh8zdUBxUA1NxbxVAS78vTPq4rCb8OUZI9xFw=
 github.com/ryanrolds/sqlclosecheck v0.3.0/go.mod h1:1gREqxyTGR3lVtpngyFo3hZAgk0KCtEdgEkHwDbigdA=
 github.com/ryanuber/columnize v0.0.0-20160712163229-9b3edd62028f/go.mod h1:sm1tb6uqfes/u+d4ooFouqFdy9/2g9QGwK3SQygK0Ts=
+github.com/sanposhiho/wastedassign v0.1.3 h1:qIMpTh4NGZYRbFJ+DSpLoVn8F4SLciX2afRvXPefC7w=
+github.com/sanposhiho/wastedassign v0.1.3/go.mod h1:LGpq5Hsv74QaqM47WtIsRSF/ik9kqk07kchgv66tLVE=
 github.com/sean-/seed v0.0.0-20170313163322-e2103e2c3529/go.mod h1:DxrIzT+xaE7yg65j358z/aeFdxmN0P9QXhEzd20vsDc=
 github.com/securego/gosec/v2 v2.6.1 h1:+KCw+uz16FYfFyJ/A5aU6uP7mnrL+j1TbDnk1yN+8R0=
 github.com/securego/gosec/v2 v2.6.1/go.mod h1:I76p3NTHBXsGhybUW+cEQ692q2Vp+A0Z6ZLzDIZy+Ao=

pkg/golinters/wastedassign.go

@@ -0,0 +1,21 @@
+package golinters
+
+import (
+	"github.com/sanposhiho/wastedassign"
+	"golang.org/x/tools/go/analysis"
+
+	"github.com/golangci/golangci-lint/pkg/golinters/goanalysis"
+)
+
+func NewWastedAssign() *goanalysis.Linter {
+	analyzers := []*analysis.Analyzer{
+		wastedassign.Analyzer,
+	}
+
+	return goanalysis.NewLinter(
+		"wastedassign",
+		"wastedassign finds wasted assignment statements.",
+		analyzers,
+		nil,
+	).WithLoadMode(goanalysis.LoadModeTypesInfo)
+}

pkg/lint/lintersdb/manager.go

@@ -374,6 +374,10 @@ func (m Manager) GetAllSupportedLinterConfigs() []*linter.Config {
 			WithPresets(linter.PresetBugs).
 			WithLoadForGoAnalysis().
 			WithURL("https://github.com/charithe/durationcheck"),
+		linter.NewConfig(golinters.NewWastedAssign()).
+			WithPresets(linter.PresetStyle).
+			WithLoadForGoAnalysis().
+			WithURL("https://github.com/sanposhiho/wastedassign"),
 
 		// nolintlint must be last because it looks at the results of all the previous linters for unused nolint directives
 		linter.NewConfig(golinters.NewNoLintLint()).

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
+}