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// run -gcflags=-G=3
// 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.
// Test method calls on type parameters
package main
import (
"fmt"
"reflect"
"strconv"
)
// Simple constraint
type Stringer interface {
String() string
}
func stringify[T Stringer](s []T) (ret []string) {
for _, v := range s {
ret = append(ret, v.String())
}
return ret
}
type myint int
func (i myint) String() string {
return strconv.Itoa(int(i))
}
// Constraint with an embedded interface, but still only requires String()
type Stringer2 interface {
CanBeStringer2() int
SubStringer2
}
type SubStringer2 interface {
CanBeSubStringer2() int
String() string
}
func stringify2[T Stringer2](s []T) (ret []string) {
for _, v := range s {
ret = append(ret, v.String())
}
return ret
}
func (myint) CanBeStringer2() int {
return 0
}
func (myint) CanBeSubStringer2() int {
return 0
}
// Test use of method values that are not called
func stringify3[T Stringer](s []T) (ret []string) {
for _, v := range s {
f := v.String
ret = append(ret, f())
}
return ret
}
func main() {
x := []myint{myint(1), myint(2), myint(3)}
got := stringify(x)
want := []string{"1", "2", "3"}
if !reflect.DeepEqual(got, want) {
panic(fmt.Sprintf("got %s, want %s", got, want))
}
got = stringify2(x)
if !reflect.DeepEqual(got, want) {
panic(fmt.Sprintf("got %s, want %s", got, want))
}
got = stringify3(x)
if !reflect.DeepEqual(got, want) {
panic(fmt.Sprintf("got %s, want %s", got, want))
}
}
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