mirror of
https://github.com/golang/go
synced 2024-11-15 01:00:29 -07:00
81c5d92f52
Change-Id: I8787458f9ccd3b5cdcdda820d8a45deb4f77eade
GitHub-Last-Rev: be865d67ef
GitHub-Pull-Request: golang/go#63165
Reviewed-on: https://go-review.googlesource.com/c/go/+/530120
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
109 lines
2.7 KiB
Go
109 lines
2.7 KiB
Go
// run
|
|
|
|
// Copyright 2021 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
// This test illustrates how a type bound method (String below) can be implemented
|
|
// either by a concrete type (myint below) or an instantiated generic type
|
|
// (StringInt[myint] below).
|
|
|
|
package main
|
|
|
|
import (
|
|
"fmt"
|
|
"reflect"
|
|
"strconv"
|
|
)
|
|
|
|
type myint int
|
|
|
|
//go:noinline
|
|
func (m myint) String() string {
|
|
return strconv.Itoa(int(m))
|
|
}
|
|
|
|
type Stringer interface {
|
|
String() string
|
|
}
|
|
|
|
func stringify[T Stringer](s []T) (ret []string) {
|
|
for _, v := range s {
|
|
// Test normal bounds method call on type param
|
|
x1 := v.String()
|
|
|
|
// Test converting type param to its bound interface first
|
|
v1 := Stringer(v)
|
|
x2 := v1.String()
|
|
|
|
// Test method expression with type param type
|
|
f1 := T.String
|
|
x3 := f1(v)
|
|
|
|
// Test creating and calling closure equivalent to the method expression
|
|
f2 := func(v1 T) string {
|
|
return Stringer(v1).String()
|
|
}
|
|
x4 := f2(v)
|
|
|
|
if x1 != x2 || x2 != x3 || x3 != x4 {
|
|
panic(fmt.Sprintf("Mismatched values %v, %v, %v, %v\n", x1, x2, x3, x4))
|
|
}
|
|
|
|
ret = append(ret, v.String())
|
|
}
|
|
return ret
|
|
}
|
|
|
|
type Ints interface {
|
|
~int32 | ~int
|
|
}
|
|
|
|
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
|
|
// type StringInt[T Ints] T
|
|
//
|
|
// //go:noinline
|
|
// func (m StringInt[T]) String() string {
|
|
// return strconv.Itoa(int(m))
|
|
// }
|
|
|
|
type StringStruct[T Ints] struct {
|
|
f T
|
|
}
|
|
|
|
func (m StringStruct[T]) String() string {
|
|
return strconv.Itoa(int(m.f))
|
|
}
|
|
|
|
func main() {
|
|
x := []myint{myint(1), myint(2), myint(3)}
|
|
|
|
// stringify on a normal type, whose bound method is associated with the base type.
|
|
got := stringify(x)
|
|
want := []string{"1", "2", "3"}
|
|
if !reflect.DeepEqual(got, want) {
|
|
panic(fmt.Sprintf("got %s, want %s", got, want))
|
|
}
|
|
|
|
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
|
|
// x2 := []StringInt[myint]{StringInt[myint](5), StringInt[myint](7), StringInt[myint](6)}
|
|
//
|
|
// // stringify on an instantiated type, whose bound method is associated with
|
|
// // the generic type StringInt[T], which maps directly to T.
|
|
// got2 := stringify(x2)
|
|
// want2 := []string{"5", "7", "6"}
|
|
// if !reflect.DeepEqual(got2, want2) {
|
|
// panic(fmt.Sprintf("got %s, want %s", got2, want2))
|
|
// }
|
|
|
|
// stringify on an instantiated type, whose bound method is associated with
|
|
// the generic type StringStruct[T], which maps to a struct containing T.
|
|
x3 := []StringStruct[myint]{StringStruct[myint]{f: 11}, StringStruct[myint]{f: 10}, StringStruct[myint]{f: 9}}
|
|
|
|
got3 := stringify(x3)
|
|
want3 := []string{"11", "10", "9"}
|
|
if !reflect.DeepEqual(got3, want3) {
|
|
panic(fmt.Sprintf("got %s, want %s", got3, want3))
|
|
}
|
|
}
|