Source file test/closure2.go

     1  // run
     2  
     3  // Copyright 2015 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  // Check that these do not use "by value" capturing,
     8  // because changes are made to the value during the closure.
     9  
    10  package main
    11  
    12  var never bool
    13  
    14  func main() {
    15  	{
    16  		type X struct {
    17  			v int
    18  		}
    19  		var x X
    20  		func() {
    21  			x.v++
    22  		}()
    23  		if x.v != 1 {
    24  			panic("x.v != 1")
    25  		}
    26  
    27  		type Y struct {
    28  			X
    29  		}
    30  		var y Y
    31  		func() {
    32  			y.v = 1
    33  		}()
    34  		if y.v != 1 {
    35  			panic("y.v != 1")
    36  		}
    37  	}
    38  
    39  	{
    40  		type Z struct {
    41  			a [3]byte
    42  		}
    43  		var z Z
    44  		func() {
    45  			i := 0
    46  			for z.a[1] = 1; i < 10; i++ {
    47  			}
    48  		}()
    49  		if z.a[1] != 1 {
    50  			panic("z.a[1] != 1")
    51  		}
    52  	}
    53  
    54  	{
    55  		w := 0
    56  		tmp := 0
    57  		f := func() {
    58  			if w != 1 {
    59  				panic("w != 1")
    60  			}
    61  		}
    62  		func() {
    63  			tmp = w // force capture of w, but do not write to it yet
    64  			_ = tmp
    65  			func() {
    66  				func() {
    67  					w++ // write in a nested closure
    68  				}()
    69  			}()
    70  		}()
    71  		f()
    72  	}
    73  
    74  	{
    75  		var g func() int
    76  		for i := range [2]int{} {
    77  			if i == 0 {
    78  				g = func() int {
    79  					return i // test that we capture by ref here, i is mutated on every interaction
    80  				}
    81  			}
    82  		}
    83  		if g() != 1 {
    84  			panic("g() != 1")
    85  		}
    86  	}
    87  
    88  	{
    89  		var g func() int
    90  		q := 0
    91  		for range [2]int{} {
    92  			q++
    93  			g = func() int {
    94  				return q // test that we capture by ref here
    95  				// q++ must on a different decldepth than q declaration
    96  			}
    97  		}
    98  		if g() != 2 {
    99  			panic("g() != 2")
   100  		}
   101  	}
   102  
   103  	{
   104  		var g func() int
   105  		var a [2]int
   106  		q := 0
   107  		for a[func() int {
   108  			q++
   109  			return 0
   110  		}()] = range [2]int{} {
   111  			g = func() int {
   112  				return q // test that we capture by ref here
   113  				// q++ must on a different decldepth than q declaration
   114  			}
   115  		}
   116  		if g() != 2 {
   117  			panic("g() != 2")
   118  		}
   119  	}
   120  
   121  	{
   122  		var g func() int
   123  		q := 0
   124  		q, g = 1, func() int { return q }
   125  		if never {
   126  			g = func() int { return 2 }
   127  		}
   128  		if g() != 1 {
   129  			panic("g() != 1")
   130  		}
   131  	}
   132  }
   133  

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