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
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
use std::alloc::Layout;
use std::collections::HashMap;
use std::collections::HashSet;
use std::marker::PhantomData;
pub use gazebo_derive::Coerce;
use crate::cast::transmute_unchecked;
pub unsafe trait Coerce<To: ?Sized> {}
pub unsafe trait CoerceKey<To: ?Sized>: Coerce<To> {}
unsafe impl<'a, From: ?Sized, To: ?Sized> Coerce<&'a To> for &'a From where From: Coerce<To> {}
unsafe impl<'a, From: ?Sized, To: ?Sized> CoerceKey<&'a To> for &'a From where From: CoerceKey<To> {}
unsafe impl<From, To> Coerce<[To]> for [From] where From: Coerce<To> {}
unsafe impl<From, To> CoerceKey<[To]> for [From] where From: CoerceKey<To> {}
unsafe impl<From, To> Coerce<Vec<To>> for Vec<From> where From: Coerce<To> {}
unsafe impl<From, To> CoerceKey<Vec<To>> for Vec<From> where From: CoerceKey<To> {}
unsafe impl<From: ?Sized, To: ?Sized> CoerceKey<Box<To>> for Box<From> where From: CoerceKey<To> {}
unsafe impl<From: ?Sized, To: ?Sized> Coerce<Box<To>> for Box<From> where From: Coerce<To> {}
unsafe impl<From, To> Coerce<HashSet<To>> for HashSet<From> where From: CoerceKey<To> {}
unsafe impl<FromK, FromV, ToK, ToV> Coerce<HashMap<ToK, ToV>> for HashMap<FromK, FromV>
where
FromK: CoerceKey<ToK>,
FromV: Coerce<ToV>,
{
}
unsafe impl<From1: Coerce<To1>, To1> Coerce<(To1,)> for (From1,) {}
unsafe impl<From1: CoerceKey<To1>, To1> CoerceKey<(To1,)> for (From1,) {}
unsafe impl<From1: Coerce<To1>, From2: Coerce<To2>, To1, To2> Coerce<(To1, To2)>
for (From1, From2)
{
}
unsafe impl<From1: CoerceKey<To1>, From2: CoerceKey<To2>, To1, To2> CoerceKey<(To1, To2)>
for (From1, From2)
{
}
unsafe impl<From: Coerce<To>, To, const N: usize> Coerce<[To; N]> for [From; N] {}
unsafe impl<From: CoerceKey<To>, To, const N: usize> CoerceKey<[To; N]> for [From; N] {}
unsafe impl<From, To> Coerce<PhantomData<To>> for PhantomData<From> {}
unsafe impl Coerce<String> for String {}
unsafe impl CoerceKey<String> for String {}
unsafe impl Coerce<str> for str {}
unsafe impl CoerceKey<str> for str {}
unsafe impl Coerce<()> for () {}
unsafe impl CoerceKey<()> for () {}
#[inline]
pub fn coerce<From, To>(x: From) -> To
where
From: Coerce<To>,
{
assert_eq!(Layout::new::<From>(), Layout::new::<To>());
unsafe { transmute_unchecked(x) }
}
#[cfg(test)]
mod tests {
use std::marker;
use super::*;
use crate as gazebo;
#[test]
fn test_ptr_coerce() {
fn f<'v>(x: (&'static str,)) -> (&'v str,) {
coerce(x)
}
let x = "test".to_owned();
assert_eq!(f(("test",)), (x.as_str(),))
}
#[test]
fn test_coerce_lifetime() {
#[derive(Coerce)]
#[repr(transparent)]
struct NewtypeWithLifetime<'v>(&'v [usize]);
let newtype = NewtypeWithLifetime(&[1, 2]);
assert_eq!(&[1, 2], coerce(newtype))
}
#[test]
fn test_coerce_type_and_lifetime_params() {
#[derive(Coerce)]
#[repr(C)]
struct Aaa<'a>(&'a u32);
#[derive(Coerce)]
#[repr(C)]
struct Bbb<'a>(&'a u32);
unsafe impl<'a> Coerce<Bbb<'a>> for Aaa<'a> {}
#[derive(Coerce)]
#[repr(C)]
struct StructWithLifetimeAndTypeParams<'a, X> {
x: X,
_marker: marker::PhantomData<&'a u32>,
}
let ten = 10;
let old = StructWithLifetimeAndTypeParams::<Aaa> {
x: Aaa(&ten),
_marker: marker::PhantomData,
};
let new: StructWithLifetimeAndTypeParams<Bbb> = coerce(old);
assert_eq!(10, *new.x.0);
}
}