mirror of
https://github.com/golang/go
synced 2024-09-05 16:04:50 +00:00
a91d0b649c
We may revisit this decision in a future release. By disallowing this for Go 1.18 we are ensuring that we don't lock in the generics design in a place that may need to change later. (Type declarations are the primary construct where it crucially matters what the underlying type of a type parameter is.) Comment out all tests that rely on this feature; add comments referring to issue so we can find all places easily should we change our minds. Fixes #45639. Change-Id: I730510e4da66d3716d455a9071c7778a1e4a1152 Reviewed-on: https://go-review.googlesource.com/c/go/+/359177 Trust: Robert Griesemer <gri@golang.org> Trust: Dan Scales <danscales@google.com> Reviewed-by: Dan Scales <danscales@google.com>
41 lines
1,022 B
Go
41 lines
1,022 B
Go
// 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 Exp[Ty any] interface {
|
|
Eval() Ty
|
|
}
|
|
|
|
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
|
|
// type Lit[Ty any] Ty
|
|
//
|
|
// func (lit Lit[Ty]) Eval() Ty { return Ty(lit) }
|
|
// func (lit Lit[Ty]) String() string { return fmt.Sprintf("(lit %v)", Ty(lit)) }
|
|
|
|
type Eq[Ty any] struct {
|
|
a Exp[Ty]
|
|
b Exp[Ty]
|
|
}
|
|
|
|
func (e Eq[Ty]) String() string {
|
|
return fmt.Sprintf("(eq %v %v)", e.a, e.b)
|
|
}
|
|
|
|
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
|
|
// var (
|
|
// e0 = Eq[int]{Lit[int](128), Lit[int](64)}
|
|
// e1 = Eq[bool]{Lit[bool](true), Lit[bool](true)}
|
|
// )
|
|
|
|
func main() {
|
|
// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
|
|
// fmt.Printf("%v\n", e0)
|
|
// fmt.Printf("%v\n", e1)
|
|
}
|