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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.
50 lines
1.4 KiB
Rust
50 lines
1.4 KiB
Rust
//@ check-fail
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#![feature(extern_types, sized_hierarchy)]
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use std::marker::{MetaSized, PointeeSized};
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fn bare<T>() {}
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fn sized<T: Sized>() {}
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fn neg_sized<T: ?Sized>() {}
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fn metasized<T: MetaSized>() {}
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fn neg_metasized<T: ?MetaSized>() {}
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//~^ ERROR relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
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fn pointeesized<T: PointeeSized>() { }
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fn neg_pointeesized<T: ?PointeeSized>() { }
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//~^ ERROR relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
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fn main() {
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// Functions which should have a `T: Sized` bound - check for an error given a non-Sized type:
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bare::<[u8]>();
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//~^ ERROR the size for values of type `[u8]` cannot be known at compilation time
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sized::<[u8]>();
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//~^ ERROR the size for values of type `[u8]` cannot be known at compilation time
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metasized::<[u8]>();
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pointeesized::<[u8]>();
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// Functions which should have a `T: MetaSized` bound - check for an error given a
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// non-MetaSized type:
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unsafe extern "C" {
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type Foo;
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}
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bare::<Foo>();
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//~^ ERROR the size for values of type `main::Foo` cannot be known
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sized::<Foo>();
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//~^ ERROR the size for values of type `main::Foo` cannot be known
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metasized::<Foo>();
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//~^ ERROR the size for values of type `main::Foo` cannot be known
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pointeesized::<Foo>();
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}
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