[dev.go2go] test: drop type keyword, always provide constraint

This is a rewrite to drop the type keyword for parameterized functions
and types, and to instead always provide a constraint.

We can revert if we don't like this approach.

Change-Id: If4669fb4e2015067e9f955ff8567ed421be639ea
Reviewed-on: https://go-review.googlesource.com/c/go/+/248880
Reviewed-by: Ian Lance Taylor <iant@golang.org>

test/gen/err001.go2

@@ -6,17 +6,17 @@
 
 package p
 
-func F1[type T comparable]() {}
+func F1[T comparable]() {}
 func F2() { F1[[]int]() } // ERROR "\[\]int does not satisfy comparable$"
 
 type C interface {
 	M()
 }
 
-func F3[type T C]() {}
+func F3[T C]() {}
 func F4() { F3[int]() } // ERROR "int does not satisfy C.*method M"
 
-func F5[type T]() { F3[T]() } // ERROR "T does not satisfy C.*method M"
+func F5[T any]() { F3[T]() } // ERROR "T does not satisfy C.*method M"
 
 type signed interface {
 	type int, int8, int16, int32, int64
@@ -27,9 +27,9 @@ type integer interface {
 		uint, uint8, uint16, uint32, uint64, uintptr
 }
 
-func F6[type T signed](a T) bool { return a < 0 }
-func F7[type T](a T) bool { return F6(a) } // ERROR "T does not satisfy signed.*T has no type constraints"
-func F8[type T integer](a T) bool { return F6(a) } // ERROR "T does not satisfy signed.*T type constraint uint not found in"
+func F6[T signed](a T) bool { return a < 0 }
+func F7[T any](a T) bool { return F6(a) } // ERROR "T does not satisfy signed.*T has no type constraints"
+func F8[T integer](a T) bool { return F6(a) } // ERROR "T does not satisfy signed.*T type constraint uint not found in"
 func F9(a uint) bool { return F6(a) } // ERROR "uint does not satisfy signed.*uint not found in"
 
 type MyInt int
@@ -43,7 +43,7 @@ type C2 interface {
 	signed
 }
 
-func F20[type T C2](a T) bool {
+func F20[T C2](a T) bool {
 	a.M()
 	return a < 0
 }
@@ -57,8 +57,8 @@ func (S) M() {}
 
 func F21() bool { return F20(MyInt(0)) }
 func F22() bool { return F20(0) } // ERROR "int does not satisfy C2.*(missing method M)"
-func F23[type T](a T) bool { return F20(a) } // ERROR "T does not satisfy C2.*(missing method M)"
-func F24[type T integer](a T) bool { return F20(a) } // ERROR "T does not satisfy C2.*(missing method M)"
+func F23[T any](a T) bool { return F20(a) } // ERROR "T does not satisfy C2.*(missing method M)"
+func F24[T integer](a T) bool { return F20(a) } // ERROR "T does not satisfy C2.*(missing method M)"
 func F25(a uint) bool { return F20(a) } // ERROR "uint does not satisfy C2.*(missing method M)"
 func F26(a MyUint) bool { return F20(a) } // ERROR "MyUint does not satisfy C2.*uint not found in"
 func F27(a S) bool { return F20(a) } // ERROR "S does not satisfy C2.*struct{} not found in"

test/gen/err002.dir/b.go2

@@ -6,5 +6,5 @@ package b
 
 import "./a"
 
-func F1[type T a.C]() {}
+func F1[T a.C]() {}
 func F2() { F1(int)() } // ERROR "int does not satisfy a.C.*method M"

test/gen/err003.go2

@@ -10,7 +10,7 @@ type Setter interface {
 	Set(string)
 }
 
-func FromStrings[type T Setter](s []string) []T {
+func FromStrings[T Setter](s []string) []T {
 	result := make([]T, len(s))
 	for i, v := range s {
 		result[i].Set(v)

test/gen/err004.go2

@@ -7,5 +7,5 @@
 package p
 
 func F() {
-     type t[type T] T // ERROR "parameterized type"
+     type t[T any] T // ERROR "parameterized type"
 }

test/gen/err005.go2

@@ -7,7 +7,7 @@
 // Issue 39738.
 package p
 
-func F1[type T]() {}
+func F1[T any]() {}
 
 func F2() {
      type s struct{}

test/gen/err006.go2

@@ -7,7 +7,7 @@
 // Issue 39743.
 package p
 
-type S[type T] struct{}
+type S[T any] struct{}
 
 func (s S[_]) M() {}	// ERROR "_"
 

test/gen/g001.go2

@@ -8,7 +8,7 @@ package main
 
 import "fmt"
 
-func Print[type T](s []T) {
+func Print[T any](s []T) {
 	for _, v := range s {
 		fmt.Println(v)
 	}

test/gen/g002.go2

@@ -8,13 +8,13 @@ package main
 
 import "fmt"
 
-func Print1[type T](s []T) {
+func Print1[T any](s []T) {
 	for _, v := range s {
 		fmt.Println(v)
 	}
 }
 
-func Print2[type T](s []T) {
+func Print2[T any](s []T) {
 	Print1(T)(s)
 }
 

test/gen/g003.go2

@@ -11,7 +11,7 @@ import (
 	"unsafe"
 )
 
-type Pair[type F1, F2] struct {
+type Pair[F1, F2 any] struct {
 	f1 F1
 	f2 F2
 }

test/gen/g004.go2

@@ -8,7 +8,7 @@ package main
 
 import "fmt"
 
-type Value[type T] struct {
+type Value[T any] struct {
 	val T
 }
 

test/gen/g005.dir/a.go2

@@ -4,7 +4,7 @@
 
 package a
 
-type Stack[type E] []E
+type Stack[E any] []E
 
 func (s *Stack[E]) Push(e E) {
 	*s = append(*s, e)

test/gen/g006.go2

@@ -20,7 +20,7 @@ type Ordered interface {
 		string
 }
 
-type orderedSlice[type Elem Ordered] []Elem
+type orderedSlice[Elem Ordered] []Elem
 
 func (s orderedSlice[Elem]) Len() int           { return len(s) }
 func (s orderedSlice[Elem]) Less(i, j int) bool {
@@ -35,7 +35,7 @@ func (s orderedSlice[Elem]) Less(i, j int) bool {
 }
 func (s orderedSlice[Elem]) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
 
-func OrderedSlice[type Elem Ordered](s []Elem) {
+func OrderedSlice[Elem Ordered](s []Elem) {
 	sort.Sort(orderedSlice[Elem](s))
 }
 
@@ -55,7 +55,7 @@ func TestSortOrderedStrings() bool {
 	return testOrdered("strings", strings, sort.Strings)
 }
 
-func testOrdered[type Elem Ordered](name string, s []Elem, sorter func([]Elem)) bool {
+func testOrdered[Elem Ordered](name string, s []Elem, sorter func([]Elem)) bool {
 	s1 := make([]Elem, len(s))
 	copy(s1, s)
 	s2 := make([]Elem, len(s))
@@ -76,7 +76,7 @@ func testOrdered[type Elem Ordered](name string, s []Elem, sorter func([]Elem))
 	return ok
 }
 
-func sliceEq[type Elem Ordered](s1, s2 []Elem) bool {
+func sliceEq[Elem Ordered](s1, s2 []Elem) bool {
 	for i, v1 := range s1 {
 		v2 := s2[i]
 		if v1 != v2 {

test/gen/g007.go2

@@ -9,11 +9,11 @@
 
 package p
 
-type S[type T] struct {
+type S[T any] struct {
 	f T
 }
 
-func SliceS[type T]() S[[]T] {
+func SliceS[T any]() S[[]T] {
 	return S[[]T]{nil}
 }
 

test/gen/g008.go2

@@ -10,7 +10,7 @@ type Setter interface {
 	Set(string)
 }
 
-func FromStrings[type T Setter](s []string) []T {
+func FromStrings[T Setter](s []string) []T {
 	result := make([]T, len(s))
 	for i, v := range s {
 		result[i].Set(v)

test/gen/g009.go2

@@ -11,12 +11,12 @@ import (
 	"strconv"
 )
 
-type Setter2[type B] interface {
+type Setter2[B any] interface {
 	Set(string)
 	type *B
 }
 
-func FromStrings2[type T interface{}, PT Setter2[T]](s []string) []T {
+func FromStrings2[T any, PT Setter2[T]](s []string) []T {
 	result := make([]T, len(s))
 	for i, v := range s {
 		p := PT(&result[i])

test/gen/g010.go2

@@ -11,7 +11,7 @@ import (
 	"strconv"
 )
 
-func FromStrings3[type T](s []string, set func(*T, string)) []T {
+func FromStrings3[T any](s []string, set func(*T, string)) []T {
 	results := make([]T, len(s))
 	for i, v := range s {
 		set(&results[i], v)

test/gen/g011.go2

@@ -15,7 +15,7 @@ type Setter interface {
 	Set(string)
 }
 
-func FromStrings[type *T Setter](s []string) []T {
+func FromStrings[*T Setter](s []string) []T {
 	result := make([]T, len(s))
 	for i, v := range s {
 		// result[i] is an addressable value of type T,

test/gen/g012.go2

@@ -16,14 +16,14 @@ type Numeric interface {
 }
 
 // NumericAbs matches numeric types with an Abs method.
-type NumericAbs[type T] interface {
+type NumericAbs[T any] interface {
 	Numeric
 	Abs() T
 }
 
 // AbsDifference computes the absolute value of the difference of
 // a and b, where the absolute value is determined by the Abs method.
-func AbsDifference[type T NumericAbs](a, b T) T {
+func AbsDifference[T NumericAbs](a, b T) T {
 	d := a - b
 	return d.Abs()
 }
@@ -42,7 +42,7 @@ type Complex interface {
 
 // OrderedAbs is a helper type that defines an Abs method for
 // ordered numeric types.
-type OrderedAbs[type T OrderedNumeric] T
+type OrderedAbs[T OrderedNumeric] T
 
 func (a OrderedAbs[T]) Abs() OrderedAbs[T] {
 	if a < 0 {
@@ -53,7 +53,7 @@ func (a OrderedAbs[T]) Abs() OrderedAbs[T] {
 
 // ComplexAbs is a helper type that defines an Abs method for
 // complex types.
-type ComplexAbs[type T Complex] T
+type ComplexAbs[T Complex] T
 
 func (a ComplexAbs[T]) Abs() ComplexAbs[T] {
 	r := float64(real(a))
@@ -64,13 +64,13 @@ func (a ComplexAbs[T]) Abs() ComplexAbs[T] {
 
 // OrderedAbsDifference returns the absolute value of the difference
 // between a and b, where a and b are of an ordered type.
-func OrderedAbsDifference[type T OrderedNumeric](a, b T) T {
+func OrderedAbsDifference[T OrderedNumeric](a, b T) T {
 	return T(AbsDifference(OrderedAbs(T)(a), OrderedAbs(T)(b)))
 }
 
 // ComplexAbsDifference returns the absolute value of the difference
 // between a and b, where a and b are of a complex type.
-func ComplexAbsDifference[type T Complex](a, b T) T {
+func ComplexAbsDifference[T Complex](a, b T) T {
 	return T(AbsDifference(ComplexAbs(T)(a), ComplexAbs(T)(b)))
 }
 

test/gen/g013.go2

@@ -6,9 +6,9 @@
 
 package main
 
-type Gen[type A] func() (A, bool)
+type Gen[A any] func() (A, bool)
 
-func combine[type T1, T2, T](g1 Gen[T1], g2 Gen[T2], join func(T1, T2) T) Gen[T] {
+func combine[T1, T2, T any](g1 Gen[T1], g2 Gen[T2], join func(T1, T2) T) Gen[T] {
     return func() (T, bool) {
         var t T
         t1, ok := g1()
@@ -23,14 +23,14 @@ func combine[type T1, T2, T](g1 Gen[T1], g2 Gen[T2], join func(T1, T2) T) Gen[T]
     }
 }
 
-type Pair[type A, B] struct {
+type Pair[A, B any] struct {
 	A A
 	B B
 }
 
-func NewPair[type A, B](a A, b B) Pair[A, B] { return Pair[A, B]{a, b} }
+func NewPair[A, B any](a A, b B) Pair[A, B] { return Pair[A, B]{a, b} }
 
-func Combine2[type A, B](ga Gen[A], gb Gen[B]) Gen[Pair[A, B]] {
+func Combine2[A, B any](ga Gen[A], gb Gen[B]) Gen[Pair[A, B]] {
     return combine(ga, gb, NewPair(A, B))
 }
 

test/gen/g014.go2

@@ -6,7 +6,7 @@
 
 package main
 
-type T[type A] struct {
+type T[A any] struct {
 	V A
 }
 

test/gen/g015.go2

@@ -6,7 +6,7 @@
 
 package p
 
-func F1[type T](x T) {}
+func F1[T any](x T) {}
 
 func F2(c <-chan int) {
 	F1(c)

test/gen/g016.go2

@@ -10,7 +10,7 @@ import "fmt"
 
 type Any interface{}
 
-type Function[type a Any, b Any] interface {
+type Function[a, b any] interface {
 	Apply(x a) b
 }
 
@@ -26,7 +26,7 @@ func (this pos) Apply(x int) bool {
 	return x > 0
 }
 
-type compose[type a Any, b Any, c Any] struct {
+type compose[a, b, c any] struct {
 	f Function[a, b]
 	g Function[b, c]
 }
@@ -35,7 +35,7 @@ func (this compose[a, b, c]) Apply(x a) c {
 	return this.g.Apply(this.f.Apply(x))
 }
 
-type Eq[type a] interface {
+type Eq[a any] interface {
 	Equal(a) bool
 }
 
@@ -45,17 +45,17 @@ func (this Int) Equal(that int) bool {
 	return int(this) == that
 }
 
-type List[type a Any] interface {
+type List[a any] interface {
 	Match(casenil Function[Nil[a], Any], casecons Function[Cons[a], Any]) Any
 }
 
-type Nil[type a Any] struct{}
+type Nil[a any] struct{}
 
 func (xs Nil[a]) Match(casenil Function[Nil[a], Any], casecons Function[Cons[a], Any]) Any {
 	return casenil.Apply(xs)
 }
 
-type Cons[type a Any] struct {
+type Cons[a any] struct {
 	Head a
 	Tail List[a]
 }
@@ -64,13 +64,13 @@ func (xs Cons[a]) Match(casenil Function[Nil[a], Any], casecons Function[Cons[a]
 	return casecons.Apply(xs)
 }
 
-type mapNil[type a Any, b Any] struct{}
+type mapNil[a, b any] struct{}
 
 func (m mapNil[a, b]) Apply(_ Nil[a]) Any {
 	return Nil[b]{}
 }
 
-type mapCons[type a Any, b Any] struct {
+type mapCons[a, b any] struct {
 	f Function[a, b]
 }
 
@@ -78,7 +78,7 @@ func (m mapCons[a, b]) Apply(xs Cons[a]) Any {
 	return Cons[b]{m.f.Apply(xs.Head), Map[a, b](m.f, xs.Tail)}
 }
 
-func Map[type a, b Any](f Function[a, b], xs List[a]) List[b] {
+func Map[a, b any](f Function[a, b], xs List[a]) List[b] {
 	return xs.Match(mapNil[a, b]{}, mapCons[a, b]{f}).(List[b])
 }
 

test/gen/g017.go2

@@ -8,11 +8,11 @@ package main
 
 type Recv <-chan int
 
-type sliceOf[type E] interface {
+type sliceOf[E any] interface {
 	type []E
 }
 
-func Append[type S sliceOf[T], T interface{}](s S, t ...T) S {
+func Append[S sliceOf[T], T any](s S, t ...T) S {
 	return append(s, t...)
 }
 

test/gen/g019.go2

@@ -13,7 +13,7 @@ func (*S1) M() {}
 type S2 struct{}
 func (S2) M() {}
 
-func F1[type T interface{ M() }](t T) {
+func F1[T interface{ M() }](t T) {
 	_ = T.M
 }
 

test/gen/g020.go2

@@ -9,12 +9,12 @@ package p
 
 type E struct{}
 
-type N[type T] struct {
+type N[T any] struct {
 	i int
 	n T
 }
 
-func F1[type T](i int, n T) N[T] {
+func F1[T any](i int, n T) N[T] {
 	return N[T]{i: i, n: n}
 }
 

test/gen/g021.go2

@@ -10,7 +10,7 @@ import "sync"
 
 // A Lockable is a value that may be safely simultaneously accessed
 // from multiple goroutines via the Get and Set methods.
-type Lockable[type T] struct {
+type Lockable[T any] struct {
 	T
 	mu sync.Mutex
 }

test/gen/g022.go2

@@ -6,6 +6,6 @@
 
 package p
 
-type F[type T] func(T) error
+type F[T any] func(T) error
 
 type instF = F[int]

test/gen/g023.go2

@@ -8,7 +8,7 @@ package p
 
 import "net/url"
 
-type S[type T] struct {
+type S[T any] struct {
 	f T
 }
 

test/gen/g024.go2

@@ -7,7 +7,7 @@
 // Issue 39672
 package p
 
-type S[type T] T
+type S[T any] T
 
 func (r S[T]) M()
 
@@ -16,7 +16,7 @@ func F() {
 	_ = x
 }
 
-func G[type T](v T)
+func G[T any](v T)
 
 func F2() {
 	G(0)

test/gen/g025.go2

@@ -7,17 +7,17 @@
 // Issue 39692
 package p
 
-type S1[type T1, T2] struct {
+type S1[T1, T2 any] struct {
 	f1 T1
 	f2 T2
 }
 
-type S2[type T1, T2] struct {
+type S2[T1, T2 any] struct {
 	f1 T1
 	f2 T2
 }
 
-func F1[type T](v T) T {
+func F1[T any](v T) T {
 	return v
 }
 

test/gen/g026.go2

@@ -9,7 +9,7 @@ package main
 
 import "io/ioutil"
 
-func F[type T1, T2](f func(T1) (T2, error)) {}
+func F[T1, T2 any](f func(T1) (T2, error)) {}
 
 func main() {
 	F(ioutil.ReadAll)

test/gen/g027.go2

@@ -7,7 +7,7 @@
 // Issue 39678, 39881.
 package p
 
-type B[type T] struct {
+type B[T any] struct {
 	T
 }
 
@@ -21,7 +21,7 @@ func F(s BC) {
 	s.F = 7
 }
 
-type Pair[type T, U] struct {
+type Pair[T, U any] struct {
 	T
 	U
 }

test/gen/g028.go2

@@ -7,7 +7,7 @@
 // Issue 39688.
 package p
 
-type S[type T] T
+type S[T any] T
 
 func (*S[T]) M() {}
 

test/gen/g029.go2

@@ -7,7 +7,7 @@
 // Issue 39741.
 package p
 
-func F[type T]() {
+func F[T any]() {
 	type S struct{}
 }
 

test/gen/g030.dir/a.go2

@@ -4,7 +4,7 @@
 
 package main
 
-func Len[type T](s []T) int {
+func Len[T any](s []T) int {
 	return len(s)
 }
 

test/gen/g031.go2

@@ -7,7 +7,7 @@
 // Issue 39737.
 package p
 
-func F1[type T]() {}
+func F1[T any]() {}
 
 func F2() {
 	F1(struct { F string `json:"f"` })()

test/gen/g032.go2

@@ -9,7 +9,7 @@ package p
 
 import "net/http"
 
-func F1[type T](f func() T) { f() }
+func F1[T any](f func() T) { f() }
 
 func F2() {
 	F1(func() *http.Request { return nil })

test/gen/g033.dir/a.go2

@@ -4,6 +4,6 @@
 
 package a
 
-type S[type T] struct {
+type S[T any] struct {
 	F T
 }

test/gen/g034.go2

@@ -8,7 +8,7 @@ package p
 
 type I interface{}
 
-type S[type T] struct {
+type S[T any] struct {
 	*T
 }
 

test/gen/g035.dir/a.go2

@@ -4,6 +4,6 @@
 
 package a
 
-type S[type T] struct {
+type S[T any] struct {
 	f T
 }

test/gen/g035.dir/b.go2

@@ -8,7 +8,7 @@ import "./a"
 
 type S = a.S
 
-func F1[type T](T) {}
+func F1[T any](T) {}
 
 func F2() { F1(S[string]{}) }
 

test/gen/g036.dir/a.go2

@@ -4,10 +4,10 @@
 
 package a
 
-type S[type T] struct {
+type S[T any] struct {
 	F T
 }
 
-func NewS[type T](v T) S[T] {
+func NewS[T any](v T) S[T] {
 	return S[T]{F: v}
 }

test/gen/g036.dir/b.go2

@@ -6,11 +6,11 @@ package main
 
 import "./a"
 
-type S[type T] struct {
+type S[T any] struct {
 	F T
 }
 
-func NewS[type T](v T) S[T] {
+func NewS[T any](v T) S[T] {
 	return S[T]{F: v}
 }
 

test/gen/g037.dir/a.go2

@@ -6,6 +6,6 @@ package a
 
 func F() {}
 
-func G[type T]() {
+func G[T any]() {
 	F()
 }

test/gen/g038.go2

@@ -6,7 +6,7 @@
 
 package main
 
-func F[type T comparable](a T) bool {
+func F[T comparable](a T) bool {
 	return a == a
 }
 

test/gen/g039.go2

@@ -6,15 +6,15 @@
 
 package p
 
-type top[type T, T2] struct {
+type top[T, T2 any] struct {
 	p *parent[T, T2]
 }
 
-type parent[type T, T2] struct {
+type parent[T, T2 any] struct {
 	child[T, T2]
 }
 
-type child[type T, T2] struct {
+type child[T, T2 any] struct {
 	T2
 }
 

test/gen/g040.go2

@@ -6,11 +6,11 @@
 
 package p
 
-type S1[type T] struct{}
+type S1[T any] struct{}
 
-type S2[type K comparable] struct{}
+type S2[K comparable] struct{}
 
-type S3[type K comparable] struct {
+type S3[K comparable] struct {
 	f map[K]*S1[*S2[K]]
 }