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// 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 file shows some examples of constraint literals with elided interfaces.
// These examples are permitted if proposal issue #48424 is accepted.
package p
// Constraint type sets of the form T, ~T, or A|B may omit the interface.
type (
_[T int] struct{}
_[T ~int] struct{}
_[T int | string] struct{}
_[T ~int | ~string] struct{}
)
func min[T int | string](x, y T) T {
if x < y {
return x
}
return y
}
func lookup[M ~map[K]V, K comparable, V any](m M, k K) V {
return m[k]
}
func deref[P ~*E, E any](p P) E {
return *p
}
func _() int {
p := new(int)
return deref(p)
}
func addrOfCopy[V any, P *V](v V) P {
return &v
}
func _() *int {
return addrOfCopy(0)
}
// A type parameter may not be embedded in an interface;
// so it can also not be used as a constraint.
func _[A any, B A /* ERROR "cannot use a type parameter as constraint" */]() {}
func _[A any, B, C A /* ERROR "cannot use a type parameter as constraint" */]() {}
// Error messages refer to the type constraint as it appears in the source.
// (No implicit interface should be exposed.)
func _[T string](x T) T {
return x /* ERROR "constrained by string" */ * x
}
func _[T int | string](x T) T {
return x /* ERROR "constrained by int | string" */ * x
}