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.
89 lines
3.0 KiB
Plaintext
89 lines
3.0 KiB
Plaintext
error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
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--> $DIR/default-bound.rs:16:21
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LL | fn neg_metasized<T: ?MetaSized>() {}
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| ^^^^^^^^^^
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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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--> $DIR/default-bound.rs:22:24
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LL | fn neg_pointeesized<T: ?PointeeSized>() { }
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| ^^^^^^^^^^^^^
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error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
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--> $DIR/default-bound.rs:29:12
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LL | bare::<[u8]>();
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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 `[u8]`
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note: required by an implicit `Sized` bound in `bare`
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--> $DIR/default-bound.rs:6:9
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LL | fn bare<T>() {}
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| ^ required by the implicit `Sized` requirement on this type parameter in `bare`
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help: consider relaxing the implicit `Sized` restriction
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LL | fn bare<T: ?Sized>() {}
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| ++++++++
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error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
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--> $DIR/default-bound.rs:31:13
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LL | sized::<[u8]>();
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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 `[u8]`
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note: required by a bound in `sized`
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--> $DIR/default-bound.rs:9:13
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LL | fn sized<T: Sized>() {}
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| ^^^^^ required by this bound in `sized`
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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/default-bound.rs:42:12
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LL | bare::<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 an implicit `Sized` bound in `bare`
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--> $DIR/default-bound.rs:6:9
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LL | fn bare<T>() {}
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| ^ required by the implicit `Sized` requirement on this type parameter in `bare`
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help: consider relaxing the implicit `Sized` restriction
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LL | fn bare<T: ?Sized>() {}
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| ++++++++
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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/default-bound.rs:44:13
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LL | 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 `sized`
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--> $DIR/default-bound.rs:9:13
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LL | fn sized<T: Sized>() {}
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| ^^^^^ required by this bound in `sized`
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error[E0277]: the size for values of type `main::Foo` cannot be known
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--> $DIR/default-bound.rs:46:17
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LL | 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 `metasized`
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--> $DIR/default-bound.rs:14:17
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LL | fn metasized<T: MetaSized>() {}
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| ^^^^^^^^^ required by this bound in `metasized`
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error: aborting due to 7 previous errors
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For more information about this error, try `rustc --explain E0277`.
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