codekingpro/portable-devtools

1// run2 3// Copyright 2021 The Go Authors. All rights reserved.4// Use of this source code is governed by a BSD-style5// license that can be found in the LICENSE file.6 7// This test illustrates how a type bound method (String below) can be implemented8// either by a concrete type (myint below) or an instantiated generic type9// (StringInt[myint] below).10 11package main12 13import (14	"fmt"15	"reflect"16	"strconv"17)18 19type myint int20 21//go:noinline22func (m myint) String() string {23	return strconv.Itoa(int(m))24}25 26type Stringer interface {27	String() string28}29 30func stringify[T Stringer](s []T) (ret []string) {31	for _, v := range s {32		// Test normal bounds method call on type param33		x1 := v.String()34 35		// Test converting type param to its bound interface first36		v1 := Stringer(v)37		x2 := v1.String()38 39		// Test method expression with type param type40		f1 := T.String41		x3 := f1(v)42 43		// Test creating and calling closure equivalent to the method expression44		f2 := func(v1 T) string {45			return Stringer(v1).String()46		}47		x4 := f2(v)48 49		if x1 != x2 || x2 != x3 || x3 != x4 {50			panic(fmt.Sprintf("Mismatched values %v, %v, %v, %v\n", x1, x2, x3, x4))51		}52 53		ret = append(ret, v.String())54	}55	return ret56}57 58type Ints interface {59	~int32 | ~int60}61 62// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).63// type StringInt[T Ints] T64//65// //go:noinline66// func (m StringInt[T]) String() string {67// 	return strconv.Itoa(int(m))68// }69 70type StringStruct[T Ints] struct {71	f T72}73 74func (m StringStruct[T]) String() string {75	return strconv.Itoa(int(m.f))76}77 78func main() {79	x := []myint{myint(1), myint(2), myint(3)}80 81	// stringify on a normal type, whose bound method is associated with the base type.82	got := stringify(x)83	want := []string{"1", "2", "3"}84	if !reflect.DeepEqual(got, want) {85		panic(fmt.Sprintf("got %s, want %s", got, want))86	}87 88	// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).89	// x2 := []StringInt[myint]{StringInt[myint](5), StringInt[myint](7), StringInt[myint](6)}90	//91	// // stringify on an instantiated type, whose bound method is associated with92	// // the generic type StringInt[T], which maps directly to T.93	// got2 := stringify(x2)94	// want2 := []string{"5", "7", "6"}95	// if !reflect.DeepEqual(got2, want2) {96	// 	panic(fmt.Sprintf("got %s, want %s", got2, want2))97	// }98 99	// stringify on an instantiated type, whose bound method is associated with100	// the generic type StringStruct[T], which maps to a struct containing T.101	x3 := []StringStruct[myint]{StringStruct[myint]{f: 11}, StringStruct[myint]{f: 10}, StringStruct[myint]{f: 9}}102 103	got3 := stringify(x3)104	want3 := []string{"11", "10", "9"}105	if !reflect.DeepEqual(got3, want3) {106		panic(fmt.Sprintf("got %s, want %s", got3, want3))107	}108}109