mirror of https://github.com/rust-lang/rust
45 lines
1.5 KiB
Rust
45 lines
1.5 KiB
Rust
// Well-formedness of nested opaque types, i.e. `impl Sized` in
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// `type Outer = impl Trait<Assoc = impl Sized>`. We check that
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// the nested type is well-formed, even though this would also
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// be implied by the item bounds of the opaque being
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// well-formed. See the comments below.
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#![feature(type_alias_impl_trait)]
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struct IsStatic<T: 'static>(T);
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trait Trait<In> {
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type Out;
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fn get(&self) -> Result<Self::Out, ()> {
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Err(())
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}
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}
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impl<T> Trait<&'static T> for () {
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type Out = IsStatic<T>;
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}
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// We could theoretically allow this (and previously did), as even
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// though the nested opaque is not well-formed, it can only be
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// used by normalizing the projection
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// <OuterOpaque1<T> as Trait<&'static T>>::Out
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// Assuming that we check that this projection is well-formed, the wf
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// of the nested opaque is implied.
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type OuterOpaque1<T> = impl Trait<&'static T, Out = impl Sized>;
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fn define<T>() -> OuterOpaque1<T> {}
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//~^ ERROR `T` may not live long enough
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fn define_rpit<T>() -> impl Trait<&'static T, Out = impl Sized> {}
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//~^ ERROR the parameter type `T` may not live long enough
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// Similar to `define` but here `impl Sized` can be referenced directly as
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// InnerOpaque<T>, so the `'static` bound is definitely required for
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// soundness.
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type InnerOpaque<T> = impl Sized;
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type OuterOpaque2<T> = impl Trait<&'static T, Out = InnerOpaque<T>>;
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fn define_nested_rpit<T>() -> OuterOpaque2<T> {}
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//~^ ERROR the parameter type `T` may not live long enough
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fn main() {}
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