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86ab2b60cd
Opting-out of `Sized` with `?Sized` is now equivalent to adding a `MetaSized` bound, and adding a `MetaSized` or `PointeeSized` bound is equivalent to removing the default `Sized` bound - this commit implements this change in `rustc_hir_analysis::hir_ty_lowering`. `MetaSized` is also added as a supertrait of all traits, as this is necessary to preserve backwards compatibility. Unfortunately, non-global where clauses being preferred over item bounds (where `PointeeSized` bounds would be proven) - which can result in errors when a `PointeeSized` supertrait/bound/predicate is added to some items. Rather than `PointeeSized` being a bound on everything, it can be the absence of a bound on everything, as `?Sized` was.
62 lines
1.7 KiB
Rust
62 lines
1.7 KiB
Rust
//@ check-fail
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#![feature(sized_hierarchy)]
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use std::marker::{MetaSized, PointeeSized};
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trait Sized_: Sized { }
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trait NegSized: ?Sized { }
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//~^ ERROR `?Trait` is not permitted in supertraits
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trait MetaSized_: MetaSized { }
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trait NegMetaSized: ?MetaSized { }
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//~^ ERROR `?Trait` is not permitted in supertraits
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trait PointeeSized_: PointeeSized { }
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trait NegPointeeSized: ?PointeeSized { }
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//~^ ERROR `?Trait` is not permitted in supertraits
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trait Bare {}
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fn requires_sized<T: Sized>() {}
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fn requires_metasized<T: MetaSized>() {}
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fn requires_pointeesized<T: PointeeSized>() {}
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fn with_sized_supertrait<T: PointeeSized + Sized_>() {
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requires_sized::<T>();
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requires_metasized::<T>();
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requires_pointeesized::<T>();
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}
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fn with_metasized_supertrait<T: PointeeSized + MetaSized_>() {
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requires_sized::<T>();
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//~^ ERROR the size for values of type `T` cannot be known at compilation time
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requires_metasized::<T>();
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requires_pointeesized::<T>();
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}
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// It isn't really possible to write this one..
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fn with_pointeesized_supertrait<T: PointeeSized + PointeeSized_>() {
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requires_sized::<T>();
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//~^ ERROR the size for values of type `T` cannot be known
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requires_metasized::<T>();
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//~^ ERROR the size for values of type `T` cannot be known
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requires_pointeesized::<T>();
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}
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// `T` won't inherit the `const MetaSized` implicit supertrait of `Bare`, so there is an error on
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// the bound, which is expected.
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fn with_bare_trait<T: PointeeSized + Bare>() {
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//~^ ERROR the size for values of type `T` cannot be known
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requires_sized::<T>();
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//~^ ERROR the size for values of type `T` cannot be known
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requires_metasized::<T>();
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//~^ ERROR the size for values of type `T` cannot be known
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requires_pointeesized::<T>();
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}
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fn main() { }
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