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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
1022 B
Go
41 lines
1022 B
Go
// run -gcflags=-G=3
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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import "fmt"
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type Exp[Ty any] interface {
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Eval() Ty
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}
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// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
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// type Lit[Ty any] Ty
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//
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// func (lit Lit[Ty]) Eval() Ty { return Ty(lit) }
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// func (lit Lit[Ty]) String() string { return fmt.Sprintf("(lit %v)", Ty(lit)) }
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type Eq[Ty any] struct {
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a Exp[Ty]
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b Exp[Ty]
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}
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func (e Eq[Ty]) String() string {
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return fmt.Sprintf("(eq %v %v)", e.a, e.b)
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}
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// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
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// var (
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// e0 = Eq[int]{Lit[int](128), Lit[int](64)}
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// e1 = Eq[bool]{Lit[bool](true), Lit[bool](true)}
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// )
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func main() {
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// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
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// fmt.Printf("%v\n", e0)
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// fmt.Printf("%v\n", e1)
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}
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