issue47740.go

     1  // run
     2  
     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.
     6  
     7  package main
     8  
     9  import "fmt"
    10  
    11  type Exp[Ty any] interface {
    12  	Eval() Ty
    13  }
    14  
    15  // For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
    16  // type Lit[Ty any] Ty
    17  //
    18  // func (lit Lit[Ty]) Eval() Ty       { return Ty(lit) }
    19  // func (lit Lit[Ty]) String() string { return fmt.Sprintf("(lit %v)", Ty(lit)) }
    20  
    21  type Eq[Ty any] struct {
    22  	a Exp[Ty]
    23  	b Exp[Ty]
    24  }
    25  
    26  func (e Eq[Ty]) String() string {
    27  	return fmt.Sprintf("(eq %v %v)", e.a, e.b)
    28  }
    29  
    30  // For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
    31  // var (
    32  // 	e0 = Eq[int]{Lit[int](128), Lit[int](64)}
    33  // 	e1 = Eq[bool]{Lit[bool](true), Lit[bool](true)}
    34  // )
    35  
    36  func main() {
    37  	// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
    38  	// fmt.Printf("%v\n", e0)
    39  	// fmt.Printf("%v\n", e1)
    40  }
    41
View as plain text