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