issue18595.go

     1  // run
     2  
     3  // Copyright 2017 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  // This test makes sure that itabs are unique.
     8  // More explicitly, we require that only one itab structure exists for the pair of
     9  // a given compile-time interface type and underlying concrete type.
    10  // Ensuring this invariant enables fixes for 18492 (improve type switch code).
    11  
    12  package main
    13  
    14  type I interface {
    15  	M()
    16  }
    17  type J interface {
    18  	M()
    19  }
    20  
    21  type T struct{}
    22  
    23  func (*T) M() {}
    24  
    25  func main() {
    26  	test1()
    27  	test2()
    28  }
    29  
    30  func test1() {
    31  	t := new(T)
    32  	var i1, i2 I
    33  	var j interface {
    34  		M()
    35  	}
    36  	i1 = t
    37  	j = t
    38  	i2 = j
    39  	if i1 != i2 {
    40  		panic("interfaces not equal")
    41  	}
    42  }
    43  
    44  func test2() {
    45  	t := new(T)
    46  	i1 := (I)(t)
    47  	i2 := (I)((interface {
    48  		M()
    49  	})((J)(t)))
    50  	if i1 != i2 {
    51  		panic("interfaces not equal")
    52  	}
    53  }
    54
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