// 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.

package main

import (
	"fmt"
)

type FooType[T any] interface {
	Foo(BarType[T])string
}
type BarType[T any] interface {
	Bar(FooType[T])string
}

type Baz[T any] T
func (l Baz[T]) Foo(v BarType[T]) string {
	return v.Bar(l)
}
type Bob[T any] T
func (l Bob[T]) Bar(v FooType[T]) string {
	if v,ok := v.(Baz[T]);ok{
		return fmt.Sprintf("%v%v",v,l)
	}
	return ""
}


func main() {
	var baz Baz[int] = 123
	var bob Bob[int] = 456

	if got, want := baz.Foo(bob), "123456"; got != want {
		panic(fmt.Sprintf("got %s want %s", got, want))
	}
}