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
|
#![feature(unsized_locals)]
pub trait Foo {
fn foo(self) -> String;
}
struct A;
impl Foo for A {
fn foo(self) -> String {
format!("hello")
}
}
struct B(i32);
impl Foo for B {
fn foo(self) -> String {
format!("{}", self.0)
}
}
struct C(String);
impl Foo for C {
fn foo(self) -> String {
self.0
}
}
struct D(Box<String>);
impl Foo for D {
fn foo(self) -> String {
*self.0
}
}
fn main() {
let x = *(Box::new(A) as Box<dyn Foo>);
assert_eq!(x.foo(), format!("hello"));
let x = *(Box::new(B(42)) as Box<dyn Foo>);
assert_eq!(x.foo(), format!("42"));
let x = *(Box::new(C(format!("jumping fox"))) as Box<dyn Foo>);
assert_eq!(x.foo(), format!("jumping fox"));
let x = *(Box::new(D(Box::new(format!("lazy dog")))) as Box<dyn Foo>);
assert_eq!(x.foo(), format!("lazy dog"));
}
|
