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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.
30 lines
771 B
Rust
30 lines
771 B
Rust
#![feature(extern_types)]
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#![feature(sized_hierarchy)]
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use std::marker::{MetaSized, PointeeSized};
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fn needs_pointeesized<T: PointeeSized>() {}
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fn needs_metasized<T: MetaSized>() {}
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fn needs_sized<T: Sized>() {}
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fn main() {
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needs_pointeesized::<u8>();
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needs_metasized::<u8>();
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needs_sized::<u8>();
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needs_pointeesized::<str>();
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needs_metasized::<str>();
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needs_sized::<str>();
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//~^ ERROR the size for values of type `str` cannot be known at compilation time
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extern "C" {
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type Foo;
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}
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needs_pointeesized::<Foo>();
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needs_metasized::<Foo>();
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//~^ ERROR the size for values of type `main::Foo` cannot be known
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needs_sized::<Foo>();
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//~^ ERROR the size for values of type `main::Foo` cannot be known at compilation time
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}
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