add preliminary support for generic code

check/check.go

@@ -21,6 +21,7 @@ import (
 	"sort"
 	"strings"
 
+	"golang.org/x/exp/typeparams"
 	"golang.org/x/tools/go/packages"
 	"golang.org/x/tools/go/ssa"
 	"golang.org/x/tools/go/ssa/ssautil"
@@ -44,7 +45,7 @@ func UnusedParams(tests, exported, debug bool, args ...string) ([]string, error)
 	return c.lines(args...)
 }
 
-// Checker finds unused parameterss in a program. You probably want to use
+// Checker finds unused parameters in a program. You probably want to use
 // UnusedParams instead, unless you want to use a *loader.Program and
 // *ssa.Program directly.
 type Checker struct {
@@ -877,8 +878,23 @@ func recvPrefix(recv *ast.FieldList) string {
 		}
 		expr = star.X
 	}
-	id := expr.(*ast.Ident)
-	return id.Name + "."
+	switch expr := expr.(type) {
+	case *ast.Ident:
+		return expr.Name + "."
+	default:
+		x, _, _, _ := typeparams.UnpackIndexExpr(expr)
+		if x == nil {
+			panic(fmt.Sprintf("unexepected receiver AST node: %T", expr))
+		}
+		return x.(*ast.Ident).Name + "."
+		// TODO: remove the use of x/exp/typeparams once we drop Go 1.17
+		// case *ast.IndexExpr:
+		// 	return expr.X.(*ast.Ident).Name + "."
+		// case *ast.IndexListExpr:
+		// 	return expr.X.(*ast.Ident).Name + "."
+		// default:
+		// 	panic(fmt.Sprintf("unexepected receiver AST node: %T", expr))
+	}
 }
 
 // multipleImpls reports whether a function has multiple implementations in the

go.mod

@@ -4,14 +4,14 @@ go 1.17
 
 require (
 	github.com/rogpeppe/go-internal v1.8.1
-	golang.org/x/tools v0.1.10
+	golang.org/x/exp/typeparams v0.0.0-20220613132600-b0d781184e0d
+	golang.org/x/tools v0.1.12-0.20220628192153-7743d1d949f1
 )
 
 require (
 	github.com/pkg/diff v0.0.0-20210226163009-20ebb0f2a09e // indirect
-	golang.org/x/mod v0.6.0-dev.0.20220106191415-9b9b3d81d5e3 // indirect
-	golang.org/x/sys v0.0.0-20220315194320-039c03cc5b86 // indirect
-	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
+	golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4 // indirect
+	golang.org/x/sys v0.0.0-20220627191245-f75cf1eec38b // indirect
 	gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 // indirect
 	gopkg.in/errgo.v2 v2.1.0 // indirect
 )

go.sum

@@ -10,8 +10,10 @@ github.com/rogpeppe/go-internal v1.8.1/go.mod h1:JeRgkft04UBgHMgCIwADu4Pn6Mtm5d4
 github.com/yuin/goldmark v1.4.1/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
-golang.org/x/mod v0.6.0-dev.0.20220106191415-9b9b3d81d5e3 h1:kQgndtyPBW/JIYERgdxfwMYh3AVStj88WQTlNDi2a+o=
-golang.org/x/mod v0.6.0-dev.0.20220106191415-9b9b3d81d5e3/go.mod h1:3p9vT2HGsQu2K1YbXdKPJLVgG5VJdoTa1poYQBtP1AY=
+golang.org/x/exp/typeparams v0.0.0-20220613132600-b0d781184e0d h1:+W8Qf4iJtMGKkyAygcKohjxTk4JPsL9DpzApJ22m5Ic=
+golang.org/x/exp/typeparams v0.0.0-20220613132600-b0d781184e0d/go.mod h1:AbB0pIl9nAr9wVwH+Z2ZpaocVmF5I4GyWCDIsVjR0bk=
+golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4 h1:6zppjxzCulZykYSLyVDYbneBfbaBIQPYMevg0bEwv2s=
+golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/net v0.0.0-20211015210444-4f30a5c0130f/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
@@ -22,21 +24,18 @@ golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20211019181941-9d821ace8654/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220315194320-039c03cc5b86 h1:A9i04dxx7Cribqbs8jf3FQLogkL/CV2YN7hj9KWJCkc=
-golang.org/x/sys v0.0.0-20220315194320-039c03cc5b86/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20220627191245-f75cf1eec38b h1:2n253B2r0pYSmEV+UNCQoPfU/FiaizQEK5Gu4Bq4JE8=
+golang.org/x/sys v0.0.0-20220627191245-f75cf1eec38b/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
-golang.org/x/tools v0.1.10 h1:QjFRCZxdOhBJ/UNgnBZLbNV13DlbnK0quyivTnXJM20=
-golang.org/x/tools v0.1.10/go.mod h1:Uh6Zz+xoGYZom868N8YTex3t7RhtHDBrE8Gzo9bV56E=
+golang.org/x/tools v0.1.12-0.20220628192153-7743d1d949f1 h1:NHLFZ56qCjD+0hYY3kE5Wl40Z7q4Gn9Ln/7YU0lsGko=
+golang.org/x/tools v0.1.12-0.20220628192153-7743d1d949f1/go.mod h1:SgwaegtQh8clINPpECJMqnxLv9I09HLqnW3RMqW0CA4=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
-golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=

testdata/scripts/build_tags.txt

@@ -3,6 +3,8 @@ cmp stdout stdout.golden
 
 -- go.mod --
 module testdata.tld/foo
+
+go 1.18
 -- stdout.golden --
 foo_main.go:5:23: oneUnusedMain - b is unused
 foo_main.go:24:22: multImplsMethod - f is unused
@@ -12,6 +14,7 @@ package foo
 var DoWork func()
 
 type FooType int
+
 -- foo_main.go --
 //+build !other
 
@@ -40,6 +43,7 @@ func multImplsMethod(f int) uint64 {
 	DoWork()
 	return 3
 }
+
 -- foo_other.go --
 //+build other
 

testdata/scripts/typeparams.txt

@@ -0,0 +1,91 @@
+[!go1.18] skip
+
+# TODO: catch unusedGeneric.
+unparam .
+
+-- stdout.golden --
+-- go.mod --
+module testdata.tld/foo
+
+go 1.18
+-- foo.go --
+package foo
+
+var DoWork func()
+
+func GenericFunc[GenericParamA, B any](x GenericParamA, y B) {}
+
+type GenericVector[GenericParamT any] []GenericParamT
+
+type GenericGraph[T any] struct {
+	Content T
+	Edges []GenericGraph[T]
+}
+
+type PredeclaredSignedInteger interface {
+	int | int8 | int16 | int32 | int64
+}
+
+type StringableSignedInteger interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64
+
+	String() string
+}
+
+type CombineEmbeds interface {
+	string | int
+
+	interface { EmbeddedMethod() }
+	RegularMethod()
+}
+
+type Tuple[T1 any, T2 any] struct {
+	left  T1
+	right T2
+}
+
+func (t Tuple[T1, T2]) Left() T1  { return t.left }
+func (t Tuple[T1, T2]) Right() T2 { return t.right }
+
+func (t Tuple[T1, T2]) unusedGeneric(t1 T1, t2 T2) T2 {
+	DoWork()
+	return t2
+}
+
+// otherwise Tuple isn't reachable.
+var Sink interface{} = new(Tuple[int, string])
+
+// The different number of type parameters result in different receiver AST
+// nodes on methods: IndexExpr and IndexListExpr.
+type GenericType1[T1 any] []T1
+type GenericType2[T1 any, T2 any] struct {
+	t1 T1
+	t2 T2
+}
+
+-- foo_main.go --
+//+build !other
+
+package foo
+
+func (g *GenericType1[T1]) multImplsMethodGeneric(f1 T1) {
+	DoWork()
+}
+
+func (g GenericType2[T1, T2]) multImplsMethodGeneric(f1 T1, f2 T2) T2 {
+	DoWork()
+	return f2
+}
+-- foo_other.go --
+//+build other
+
+package foo
+
+func (g *GenericType1[T1]) multImplsMethodGeneric(f1 T1) {
+	DoWork()
+}
+
+func (g GenericType2[T1, T2]) multImplsMethodGeneric(f1 T1, f2 T2) T2 {
+	DoWork()
+	return f2
+}