issue21687.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  // Issue 21687: cmd/compile evaluates x twice in "x op= y", which was
     8  // detectable if evaluating y affects x.
     9  
    10  package main
    11  
    12  func ptrs() (int, int) {
    13  	one := 1
    14  	two := 2
    15  
    16  	x := &one
    17  	*x += func() int {
    18  		x = &two
    19  		return 0
    20  	}()
    21  
    22  	return one, two
    23  }
    24  
    25  func slices() (int, int) {
    26  	one := []int{1}
    27  	two := []int{2}
    28  
    29  	x := one
    30  	x[0] += func() int {
    31  		x = two
    32  		return 0
    33  	}()
    34  
    35  	return one[0], two[0]
    36  }
    37  
    38  func maps() (int, int) {
    39  	one := map[int]int{0: 1}
    40  	two := map[int]int{0: 2}
    41  
    42  	x := one
    43  	x[0] += func() int {
    44  		x = two
    45  		return 0
    46  	}()
    47  
    48  	return one[0], two[0]
    49  }
    50  
    51  var tests = [...]func() (int, int){
    52  	ptrs,
    53  	slices,
    54  	maps,
    55  }
    56  
    57  func main() {
    58  	bad := 0
    59  	for i, f := range tests {
    60  		if a, b := f(); a+b != 3 {
    61  			println(i, a, b)
    62  			bad++
    63  		}
    64  	}
    65  	if bad != 0 {
    66  		panic(bad)
    67  	}
    68  }
    69
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