mirror of https://github.com/rust-lang/rust.git
Do not require associated types with Self: Sized to uphold bounds when confirming object candidate
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07fc644132
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@ -354,9 +354,9 @@ pub(in crate::solve) fn predicates_for_object_candidate<'tcx>(
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// FIXME(associated_const_equality): Also add associated consts to
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// FIXME(associated_const_equality): Also add associated consts to
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// the requirements here.
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// the requirements here.
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if item.kind == ty::AssocKind::Type {
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if item.kind == ty::AssocKind::Type {
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// RPITITs are not checked here, since they are not (currently) object-safe
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// associated types that require `Self: Sized` do not show up in the built-in
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// and cannot be named from a non-`Self: Sized` method.
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// implementation of `Trait for dyn Trait`, and can be dropped here.
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if item.is_impl_trait_in_trait() {
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if tcx.generics_require_sized_self(item.def_id) {
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continue;
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continue;
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}
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}
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@ -535,9 +535,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
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let assoc_types: Vec<_> = tcx
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let assoc_types: Vec<_> = tcx
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.associated_items(trait_predicate.def_id())
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.associated_items(trait_predicate.def_id())
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.in_definition_order()
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.in_definition_order()
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// RPITITs are not checked here, since they are not (currently) object-safe
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// Associated types that require `Self: Sized` do not show up in the built-in
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// and cannot be named from a non-`Self: Sized` method.
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// implementation of `Trait for dyn Trait`, and can be dropped here.
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.filter(|item| !item.is_impl_trait_in_trait())
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.filter(|item| !tcx.generics_require_sized_self(item.def_id))
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.filter_map(
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.filter_map(
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|item| if item.kind == ty::AssocKind::Type { Some(item.def_id) } else { None },
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|item| if item.kind == ty::AssocKind::Type { Some(item.def_id) } else { None },
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)
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)
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@ -19,4 +19,5 @@ fn main() {
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//~| ERROR the trait `Foo` cannot be made into an object
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//~| ERROR the trait `Foo` cannot be made into an object
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let s = i.baz();
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let s = i.baz();
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//~^ ERROR the trait `Foo` cannot be made into an object
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//~^ ERROR the trait `Foo` cannot be made into an object
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//~| ERROR the trait `Foo` cannot be made into an object
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}
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}
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@ -13,6 +13,21 @@ LL | fn baz(&self) -> impl Debug;
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| ^^^^^^^^^^ ...because method `baz` references an `impl Trait` type in its return type
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| ^^^^^^^^^^ ...because method `baz` references an `impl Trait` type in its return type
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= help: consider moving `baz` to another trait
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= help: consider moving `baz` to another trait
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error[E0038]: the trait `Foo` cannot be made into an object
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--> $DIR/object-safety.rs:20:15
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LL | let s = i.baz();
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| ^^^ `Foo` cannot be made into an object
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note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
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--> $DIR/object-safety.rs:7:22
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LL | trait Foo {
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| --- this trait cannot be made into an object...
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LL | fn baz(&self) -> impl Debug;
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| ^^^^^^^^^^ ...because method `baz` references an `impl Trait` type in its return type
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= help: consider moving `baz` to another trait
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error[E0038]: the trait `Foo` cannot be made into an object
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error[E0038]: the trait `Foo` cannot be made into an object
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--> $DIR/object-safety.rs:20:13
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--> $DIR/object-safety.rs:20:13
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@ -44,6 +59,6 @@ LL | fn baz(&self) -> impl Debug;
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= help: consider moving `baz` to another trait
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= help: consider moving `baz` to another trait
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= note: required for the cast from `Box<u32>` to `Box<dyn Foo>`
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= note: required for the cast from `Box<u32>` to `Box<dyn Foo>`
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error: aborting due to 3 previous errors
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error: aborting due to 4 previous errors
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For more information about this error, try `rustc --explain E0038`.
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For more information about this error, try `rustc --explain E0038`.
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@ -1,6 +1,5 @@
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//! This test checks that even if some associated types have
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//! This test checks that associated types with `Self: Sized` cannot be projected
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//! `where Self: Sized` bounds, those without still need to be
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//! from a `dyn Trait`.
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//! mentioned in trait objects.
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trait Bop {
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trait Bop {
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type Bar: Default
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type Bar: Default
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@ -16,5 +15,4 @@ fn bop<T: Bop + ?Sized>() {
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fn main() {
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fn main() {
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bop::<dyn Bop>();
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bop::<dyn Bop>();
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//~^ ERROR: the size for values of type `dyn Bop` cannot be known at compilation time
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}
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}
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@ -1,5 +1,5 @@
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error[E0599]: the function or associated item `default` exists for associated type `<T as Bop>::Bar`, but its trait bounds were not satisfied
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error[E0599]: the function or associated item `default` exists for associated type `<T as Bop>::Bar`, but its trait bounds were not satisfied
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--> $DIR/assoc_type_bounds_sized_used.rs:12:30
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--> $DIR/assoc_type_bounds_sized_used.rs:11:30
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LL | let _ = <T as Bop>::Bar::default();
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LL | let _ = <T as Bop>::Bar::default();
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| ^^^^^^^ function or associated item cannot be called on `<T as Bop>::Bar` due to unsatisfied trait bounds
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| ^^^^^^^ function or associated item cannot be called on `<T as Bop>::Bar` due to unsatisfied trait bounds
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@ -13,7 +13,7 @@ LL | fn bop<T: Bop + ?Sized>() where T: Sized {
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| ++++++++++++++
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| ++++++++++++++
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error[E0277]: the size for values of type `T` cannot be known at compilation time
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error[E0277]: the size for values of type `T` cannot be known at compilation time
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--> $DIR/assoc_type_bounds_sized_used.rs:12:14
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--> $DIR/assoc_type_bounds_sized_used.rs:11:14
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LL | fn bop<T: Bop + ?Sized>() {
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LL | fn bop<T: Bop + ?Sized>() {
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| - this type parameter needs to be `Sized`
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| - this type parameter needs to be `Sized`
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@ -21,7 +21,7 @@ LL | let _ = <T as Bop>::Bar::default();
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| ^ doesn't have a size known at compile-time
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| ^ doesn't have a size known at compile-time
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note: required by a bound in `Bop::Bar`
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note: required by a bound in `Bop::Bar`
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--> $DIR/assoc_type_bounds_sized_used.rs:8:15
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--> $DIR/assoc_type_bounds_sized_used.rs:7:15
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LL | type Bar: Default
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LL | type Bar: Default
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| --- required by a bound in this associated type
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| --- required by a bound in this associated type
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@ -34,20 +34,7 @@ LL - fn bop<T: Bop + ?Sized>() {
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LL + fn bop<T: Bop>() {
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LL + fn bop<T: Bop>() {
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error[E0277]: the size for values of type `dyn Bop` cannot be known at compilation time
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error: aborting due to 2 previous errors
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--> $DIR/assoc_type_bounds_sized_used.rs:18:11
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LL | bop::<dyn Bop>();
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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 `dyn Bop`
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note: required by a bound in `bop`
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--> $DIR/assoc_type_bounds_sized_used.rs:11:11
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LL | fn bop<T: Bop + ?Sized>() {
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| ^^^ required by this bound in `bop`
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error: aborting due to 3 previous errors
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Some errors have detailed explanations: E0277, E0599.
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Some errors have detailed explanations: E0277, E0599.
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For more information about an error, try `rustc --explain E0277`.
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For more information about an error, try `rustc --explain E0277`.
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@ -0,0 +1,25 @@
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// check-pass
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// revisions: current next
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//[next] compile-flags: -Ztrait-solver=next
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trait Foo {
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type Bar<'a>
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where
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Self: Sized;
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fn test(&self);
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}
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impl Foo for () {
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type Bar<'a> = () where Self: Sized;
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fn test(&self) {}
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}
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fn test(x: &dyn Foo) {
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x.test();
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}
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fn main() {
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test(&());
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}
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