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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 generic constraint interfaces.
package p
type (
// Type lists are processed as unions but an error is reported.
// TODO(gri) remove this once the parser doesn't accept type lists anymore.
_ interface{
type /* ERROR use generalized embedding syntax instead of a type list */ int
}
_ interface{
type /* ERROR use generalized embedding syntax instead of a type list */ int
type float32
}
)
type (
// Arbitrary types may be embedded like interfaces.
_ interface{int}
_ interface{~int}
// Types may be combined into a union.
_ interface{int|~string}
// Union terms must be unique independent of whether they are ~ or not.
_ interface{int|int /* ERROR duplicate term int */ }
_ interface{int|~ /* ERROR duplicate term int */ int }
_ interface{~int|~ /* ERROR duplicate term int */ int }
// For now we do not permit interfaces with methods in unions.
_ interface{~ /* ERROR invalid use of ~ */ interface{}}
_ interface{int|interface /* ERROR cannot use .* in union */ { m() }}
)
type (
// Tilde is not permitted on defined types or interfaces.
foo int
bar interface{}
_ interface{foo}
_ interface{~ /* ERROR invalid use of ~ */ foo }
_ interface{~ /* ERROR invalid use of ~ */ bar }
)
// Multiple embedded union elements are intersected. The order in which they
// appear in the interface doesn't matter since intersection is a symmetric
// operation.
type myInt1 int
type myInt2 int
func _[T interface{ myInt1|myInt2; ~int }]() T { return T(0) }
func _[T interface{ ~int; myInt1|myInt2 }]() T { return T(0) }
// Here the intersections are empty - there's no type that's in the type set of T.
func _[T interface{ myInt1|myInt2; int }]() T { return T(0 /* ERROR cannot convert */ ) }
func _[T interface{ int; myInt1|myInt2 }]() T { return T(0 /* ERROR cannot convert */ ) }
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