95 lines
1.7 KiB
Rust
95 lines
1.7 KiB
Rust
// run-pass
|
|
|
|
#![feature(trait_upcasting)]
|
|
|
|
trait Foo: PartialEq<i32> + std::fmt::Debug + Send + Sync {
|
|
fn a(&self) -> i32 {
|
|
10
|
|
}
|
|
|
|
fn z(&self) -> i32 {
|
|
11
|
|
}
|
|
|
|
fn y(&self) -> i32 {
|
|
12
|
|
}
|
|
}
|
|
|
|
trait Bar: Foo {
|
|
fn b(&self) -> i32 {
|
|
20
|
|
}
|
|
|
|
fn w(&self) -> i32 {
|
|
21
|
|
}
|
|
}
|
|
|
|
trait Baz: Bar {
|
|
fn c(&self) -> i32 {
|
|
30
|
|
}
|
|
}
|
|
|
|
impl Foo for i32 {
|
|
fn a(&self) -> i32 {
|
|
100
|
|
}
|
|
}
|
|
|
|
impl Bar for i32 {
|
|
fn b(&self) -> i32 {
|
|
200
|
|
}
|
|
}
|
|
|
|
impl Baz for i32 {
|
|
fn c(&self) -> i32 {
|
|
300
|
|
}
|
|
}
|
|
|
|
// Note: upcast lifetime means a shorter lifetime.
|
|
fn upcast_baz<'a: 'b, 'b, T>(v: Box<dyn Baz + 'a>, _l: &'b T) -> Box<dyn Baz + 'b> {
|
|
v
|
|
}
|
|
fn upcast_bar<'a: 'b, 'b, T>(v: Box<dyn Bar + 'a>, _l: &'b T) -> Box<dyn Bar + 'b> {
|
|
v
|
|
}
|
|
fn upcast_foo<'a: 'b, 'b, T>(v: Box<dyn Foo + 'a>, _l: &'b T) -> Box<dyn Foo + 'b> {
|
|
v
|
|
}
|
|
|
|
fn main() {
|
|
let v = Box::new(1);
|
|
let l = &(); // dummy lifetime (shorter than `baz`)
|
|
|
|
let baz: Box<dyn Baz> = v.clone();
|
|
let u = upcast_baz(baz, &l);
|
|
assert_eq!(*u, 1);
|
|
assert_eq!(u.a(), 100);
|
|
assert_eq!(u.b(), 200);
|
|
assert_eq!(u.c(), 300);
|
|
|
|
let baz: Box<dyn Baz> = v.clone();
|
|
let bar: Box<dyn Bar> = baz;
|
|
let u = upcast_bar(bar, &l);
|
|
assert_eq!(*u, 1);
|
|
assert_eq!(u.a(), 100);
|
|
assert_eq!(u.b(), 200);
|
|
|
|
let baz: Box<dyn Baz> = v.clone();
|
|
let foo: Box<dyn Foo> = baz;
|
|
let u = upcast_foo(foo, &l);
|
|
assert_eq!(*u, 1);
|
|
assert_eq!(u.a(), 100);
|
|
|
|
let baz: Box<dyn Baz> = v.clone();
|
|
let bar: Box<dyn Bar> = baz;
|
|
let foo: Box<dyn Foo> = bar;
|
|
let u = upcast_foo(foo, &l);
|
|
assert_eq!(*u, 1);
|
|
assert_eq!(u.a(), 100);
|
|
}
|