mirror of https://github.com/rust-lang/rust
55 lines
1.2 KiB
Rust
55 lines
1.2 KiB
Rust
//@ check-pass
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use std::marker::PhantomData;
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pub struct Id<'id>(PhantomData<fn(&'id ()) -> &'id ()>);
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fn new_id() -> Id<'static> {
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Id(PhantomData)
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}
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pub trait HasLifetime where {
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type AtLifetime<'a>;
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}
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pub struct ExistentialLifetime<S: HasLifetime>(S::AtLifetime<'static>);
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impl<S: HasLifetime> ExistentialLifetime<S> {
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pub fn new<F>(f: F) -> ExistentialLifetime<S>
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where for<'id> F: FnOnce(Id<'id>) -> S::AtLifetime<'id> {
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ExistentialLifetime(f(new_id()))
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}
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}
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struct ExampleS<'id>(Id<'id>);
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struct ExampleMarker;
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impl HasLifetime for ExampleMarker {
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type AtLifetime<'id> = ExampleS<'id>;
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}
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fn broken0() -> ExistentialLifetime<ExampleMarker> {
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fn new_helper<'id>(id: Id<'id>) -> ExampleS<'id> {
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ExampleS(id)
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}
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ExistentialLifetime::<ExampleMarker>::new(new_helper)
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}
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fn broken1() -> ExistentialLifetime<ExampleMarker> {
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fn new_helper<'id>(id: Id<'id>) -> <ExampleMarker as HasLifetime>::AtLifetime<'id> {
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ExampleS(id)
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}
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ExistentialLifetime::<ExampleMarker>::new(new_helper)
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}
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fn broken2() -> ExistentialLifetime<ExampleMarker> {
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ExistentialLifetime::<ExampleMarker>::new(|id| ExampleS(id))
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}
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fn main() {}
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