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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.
43 lines
1.6 KiB
Plaintext
43 lines
1.6 KiB
Plaintext
error[E0277]: the size for values of type `str` cannot be known at compilation time
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--> $DIR/feature-gate-sized-hierarchy.rs:17:19
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LL | needs_sized::<str>();
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| ^^^ doesn't have a size known at compile-time
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= help: the trait `Sized` is not implemented for `str`
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note: required by a bound in `needs_sized`
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--> $DIR/feature-gate-sized-hierarchy.rs:8:19
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LL | fn needs_sized<T: Sized>() {}
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| ^^^^^ required by this bound in `needs_sized`
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error[E0277]: the size for values of type `main::Foo` cannot be known
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--> $DIR/feature-gate-sized-hierarchy.rs:25:23
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LL | needs_metasized::<Foo>();
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| ^^^ doesn't have a known size
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= help: the trait `MetaSized` is not implemented for `main::Foo`
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note: required by a bound in `needs_metasized`
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--> $DIR/feature-gate-sized-hierarchy.rs:7:23
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LL | fn needs_metasized<T: MetaSized>() {}
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| ^^^^^^^^^ required by this bound in `needs_metasized`
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error[E0277]: the size for values of type `main::Foo` cannot be known at compilation time
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--> $DIR/feature-gate-sized-hierarchy.rs:27:19
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LL | needs_sized::<Foo>();
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| ^^^ doesn't have a size known at compile-time
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= help: the trait `Sized` is not implemented for `main::Foo`
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note: required by a bound in `needs_sized`
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--> $DIR/feature-gate-sized-hierarchy.rs:8:19
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LL | fn needs_sized<T: Sized>() {}
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| ^^^^^ required by this bound in `needs_sized`
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error: aborting due to 3 previous errors
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For more information about this error, try `rustc --explain E0277`.
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