1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
|
// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
func a() (r string) {
s := "initial"
var p *struct{ i int }
defer func() {
recover()
r = s
}()
s, p.i = "set", 2 // s must be set before p.i panics
return "unreachable"
}
func b() (r string) {
s := "initial"
fn := func() []int { panic("") }
defer func() {
recover()
r = s
}()
s, fn()[0] = "set", 2 // fn() panics before any assignment occurs
return "unreachable"
}
func c() (r string) {
s := "initial"
var p map[int]int
defer func() {
recover()
r = s
}()
s, p[0] = "set", 2 //s must be set before p[0] index panics"
return "unreachable"
}
func d() (r string) {
s := "initial"
var p map[int]int
defer func() {
recover()
r = s
}()
fn := func() int { panic("") }
s, p[0] = "set", fn() // fn() panics before s is set
return "unreachable"
}
func e() (r string) {
s := "initial"
p := map[int]int{}
defer func() {
recover()
r = s
}()
fn := func() int { panic("") }
s, p[fn()] = "set", 0 // fn() panics before any assignment occurs
return "unreachable"
}
func f() (r string) {
s := "initial"
p := []int{}
defer func() {
recover()
r = s
}()
s, p[1] = "set", 0 // p[1] panics after s is set
return "unreachable"
}
func g() (r string) {
s := "initial"
p := map[any]any{}
defer func() {
recover()
r = s
}()
var i any = func() {}
s, p[i] = "set", 0 // p[i] panics after s is set
return "unreachable"
}
func h() (r string) {
fail := false
defer func() {
recover()
if fail {
r = "fail"
} else {
r = "success"
}
}()
type T struct{ f int }
var p *struct{ *T }
// The implicit "p.T" operand should be evaluated in phase 1 (and panic),
// before the "fail = true" assignment in phase 2.
fail, p.f = true, 0
return "unreachable"
}
func main() {
for _, test := range []struct {
fn func() string
want string
desc string
}{
{a, "set", "s must be set before p.i panics"},
{b, "initial", "p() panics before s is set"},
{c, "set", "s must be set before p[0] index panics"},
{d, "initial", "fn() panics before s is set"},
{e, "initial", "fn() panics before s is set"},
{f, "set", "p[1] panics after s is set"},
{g, "set", "p[i] panics after s is set"},
{h, "success", "p.T panics before fail is set"},
} {
if test.fn() != test.want {
panic(test.desc)
}
}
}
|
