3 // Copyright 2021 The Go Authors. All rights reserved.
4 // Use of this source code is governed by a BSD-style
5 // license that can be found in the LICENSE file.
9 type I[T any] interface {
13 type J[T any] interface {
19 func f[T J[T]](x T, g func(T) T) I[T] {
20 // contains a cast between two nonempty interfaces
21 // Also make sure we don't evaluate g(x) twice.
22 return I[T](J[T](g(x)))
45 panic("multiple calls")