// run

// Copyright 2020 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.

// Issue 41216.

package main

func main() {
	ps := FromStrings2[X]([]string{"x", "y"})
	if len(ps) != 2 || ps[0] != (X{"x"}) || ps[1] != (X{"y"}) {
		panic(ps)
	}
}

type X struct {
	s string
}

func (x *X) Set(s string) {
	x.s = s
}

// Setter2 is a type constraint that requires that the type
// implement a Set method that sets the value from a string,
// and also requires that the type be a pointer to its type parameter.
type Setter2[B any] interface {
	Set(string)
	type *B
}

// FromStrings2 takes a slice of strings and returns a slice of T,
// calling the Set method to set each returned value.
//
// We use two different type parameters so that we can return
// a slice of type T but call methods on *T aka PT.
// The Setter2 constraint ensures that PT is a pointer to T.
func FromStrings2[T any, PT Setter2[T]](s []string) []T {
	result := make([]T, len(s))
	for i, v := range s {
		// The type of &result[i] is *T which is in the type list
		// of Setter2, so we can convert it to PT.
		p := PT(&result[i])
		// PT has a Set method.
		p.Set(v)
	}
	return result
}