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Remove generic_associated_types_extended feature gate

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This commit is contained in:
Michael Goulet 2024-12-03 16:34:42 +00:00
parent 8575f8f91b
commit f91fd0cb87
24 changed files with 300 additions and 124 deletions
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7
compiler/rustc_feature/src/removed.rs
View file

@ -119,6 +119,13 @@ declare_features! (
(removed, generator_clone, "1.65.0", Some(95360), Some("renamed to `coroutine_clone`")),
/// Allows defining generators.
(removed, generators, "1.21.0", Some(43122), Some("renamed to `coroutines`")),
/// An extension to the `generic_associated_types` feature, allowing incomplete features.
(removed, generic_associated_types_extended, "CURRENT_RUSTC_VERSION", Some(95451),
Some(
"feature needs overhaul and reimplementation pending \
better implied higher-ranked implied bounds support"
)
),
/// Allows `impl Trait` in bindings (`let`, `const`, `static`).
(removed, impl_trait_in_bindings, "1.55.0", Some(63065),
Some("the implementation was not maintainable, the feature may get reintroduced once the current refactorings are done")),

2
compiler/rustc_feature/src/unstable.rs
View file

@ -497,8 +497,6 @@ declare_features! (
(unstable, gen_blocks, "1.75.0", Some(117078)),
/// Infer generic args for both consts and types.
(unstable, generic_arg_infer, "1.55.0", Some(85077)),
/// An extension to the `generic_associated_types` feature, allowing incomplete features.
(incomplete, generic_associated_types_extended, "1.61.0", Some(95451)),
/// Allows non-trivial generic constants which have to have wfness manually propagated to callers
(incomplete, generic_const_exprs, "1.56.0", Some(76560)),
/// Allows generic parameters and where-clauses on free & associated const items.

5
compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
View file

@ -329,10 +329,7 @@ pub fn dyn_compatibility_violations_for_assoc_item(
.collect(),
// Associated types can only be dyn-compatible if they have `Self: Sized` bounds.
ty::AssocKind::Type => {
if !tcx.features().generic_associated_types_extended()
&& !tcx.generics_of(item.def_id).is_own_empty()
&& !item.is_impl_trait_in_trait()
{
if !tcx.generics_of(item.def_id).is_own_empty() && !item.is_impl_trait_in_trait() {
vec![DynCompatibilityViolation::GAT(item.name, item.ident(tcx).span)]
} else {
// We will permit associated types if they are explicitly mentioned in the trait object.

26
compiler/rustc_trait_selection/src/traits/project.rs
View file

@ -14,7 +14,7 @@ use rustc_middle::traits::select::OverflowError;
use rustc_middle::traits::{BuiltinImplSource, ImplSource, ImplSourceUserDefinedData};
use rustc_middle::ty::fast_reject::DeepRejectCtxt;
use rustc_middle::ty::fold::TypeFoldable;
use rustc_middle::ty::visit::{MaxUniverse, TypeVisitable, TypeVisitableExt};
use rustc_middle::ty::visit::TypeVisitableExt;
use rustc_middle::ty::{self, Term, Ty, TyCtxt, TypingMode, Upcast};
use rustc_middle::{bug, span_bug};
use rustc_span::symbol::sym;
@ -179,35 +179,11 @@ pub(super) fn poly_project_and_unify_term<'cx, 'tcx>(
) -> ProjectAndUnifyResult<'tcx> {
let infcx = selcx.infcx;
let r = infcx.commit_if_ok(|_snapshot| {
let old_universe = infcx.universe();
let placeholder_predicate = infcx.enter_forall_and_leak_universe(obligation.predicate);
let new_universe = infcx.universe();
let placeholder_obligation = obligation.with(infcx.tcx, placeholder_predicate);
match project_and_unify_term(selcx, &placeholder_obligation) {
ProjectAndUnifyResult::MismatchedProjectionTypes(e) => Err(e),
ProjectAndUnifyResult::Holds(obligations)
if old_universe != new_universe
&& selcx.tcx().features().generic_associated_types_extended() =>
{
// If the `generic_associated_types_extended` feature is active, then we ignore any
// obligations references lifetimes from any universe greater than or equal to the
// universe just created. Otherwise, we can end up with something like `for<'a> I: 'a`,
// which isn't quite what we want. Ideally, we want either an implied
// `for<'a where I: 'a> I: 'a` or we want to "lazily" check these hold when we
// instantiate concrete regions. There is design work to be done here; until then,
// however, this allows experimenting potential GAT features without running into
// well-formedness issues.
let new_obligations = obligations
.into_iter()
.filter(|obligation| {
let mut visitor = MaxUniverse::new();
obligation.predicate.visit_with(&mut visitor);
visitor.max_universe() < new_universe
})
.collect();
Ok(ProjectAndUnifyResult::Holds(new_obligations))
}
other => Ok(other),
}
});

2
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
View file

@ -626,7 +626,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
for assoc_type in assoc_types {
let defs: &ty::Generics = tcx.generics_of(assoc_type);
if !defs.own_params.is_empty() && !tcx.features().generic_associated_types_extended() {
if !defs.own_params.is_empty() {
tcx.dcx().span_delayed_bug(
obligation.cause.span,
"GATs in trait object shouldn't have been considered",

13
tests/crashes/131538.rs
View file

@ -1,13 +0,0 @@
//@ known-bug: #131538
#![feature(generic_associated_types_extended)]
#![feature(trivial_bounds)]
trait HealthCheck {
async fn check<const N: usize>();
}
fn do_health_check_par()
where
HealthCheck: HealthCheck,
{
}

4
tests/ui/feature-gates/feature-gate-generic_associated_types_extended.rs
View file

@ -1,4 +0,0 @@
// This feature doesn't *currently* fire on any specific code; it's just a
// behavior change. Future changes might.
#[rustc_error] //~ the
fn main() {}

12
tests/ui/feature-gates/feature-gate-generic_associated_types_extended.stderr
View file

@ -1,12 +0,0 @@
error[E0658]: the `#[rustc_error]` attribute is just used for rustc unit tests and will never be stable
--> $DIR/feature-gate-generic_associated_types_extended.rs:3:1
|
LL | #[rustc_error]
| ^^^^^^^^^^^^^^
|
= help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error: aborting due to 1 previous error
For more information about this error, try `rustc --explain E0658`.

9
tests/ui/generic-associated-types/extended/lending_iterator.rs
View file

@ -1,9 +1,4 @@
//@ revisions: base extended
//@[base] check-fail
//@[extended] check-pass
#![cfg_attr(extended, feature(generic_associated_types_extended))]
#![cfg_attr(extended, allow(incomplete_features))]
//@ known-bug: #133805
pub trait FromLendingIterator<A>: Sized {
fn from_iter<T: for<'x> LendingIterator<Item<'x> = A>>(iter: T) -> Self;
@ -11,7 +6,6 @@ pub trait FromLendingIterator<A>: Sized {
impl<A> FromLendingIterator<A> for Vec<A> {
fn from_iter<I: for<'x> LendingIterator<Item<'x> = A>>(mut iter: I) -> Self {
//[base]~^ impl has stricter
let mut v = vec![];
while let Some(item) = iter.next() {
v.push(item);
@ -32,7 +26,6 @@ pub trait LendingIterator {
Self: for<'q> LendingIterator<Item<'q> = A>,
{
<B as FromLendingIterator<A>>::from_iter(self)
//[base]~^ ERROR: does not live long enough
}
}

4
tests/ui/generic-associated-types/extended/lending_iterator.base.stderr → tests/ui/generic-associated-types/extended/lending_iterator.stderr
View file

@ -1,5 +1,5 @@
error[E0276]: impl has stricter requirements than trait
--> $DIR/lending_iterator.rs:13:45
--> $DIR/lending_iterator.rs:8:45
|
LL | fn from_iter<T: for<'x> LendingIterator<Item<'x> = A>>(iter: T) -> Self;
| ------------------------------------------------------------------------ definition of `from_iter` from trait
@ -8,7 +8,7 @@ LL | fn from_iter<I: for<'x> LendingIterator<Item<'x> = A>>(mut iter: I) ->
| ^^^^^^^^^^^^ impl has extra requirement `I: 'x`
error: `Self` does not live long enough
--> $DIR/lending_iterator.rs:34:9
--> $DIR/lending_iterator.rs:28:9
|
LL | <B as FromLendingIterator<A>>::from_iter(self)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

8
tests/ui/generic-associated-types/extended/lending_iterator_2.rs
View file

@ -1,9 +1,4 @@
//@ revisions: base extended
//@[base] check-fail
//@[extended] check-pass
#![cfg_attr(extended, feature(generic_associated_types_extended))]
#![cfg_attr(extended, allow(incomplete_features))]
//@ known-bug: #133805
pub trait FromLendingIterator<A>: Sized {
fn from_iter<T: for<'x> LendingIterator<Item<'x> = A>>(iter: T) -> Self;
@ -11,7 +6,6 @@ pub trait FromLendingIterator<A>: Sized {
impl<A> FromLendingIterator<A> for Vec<A> {
fn from_iter<I: for<'x> LendingIterator<Item<'x> = A>>(mut iter: I) -> Self {
//[base]~^ impl has stricter
let mut v = vec![];
while let Some(item) = iter.next() {
v.push(item);

2
tests/ui/generic-associated-types/extended/lending_iterator_2.base.stderr → tests/ui/generic-associated-types/extended/lending_iterator_2.stderr
View file

@ -1,5 +1,5 @@
error[E0276]: impl has stricter requirements than trait
--> $DIR/lending_iterator_2.rs:13:45
--> $DIR/lending_iterator_2.rs:8:45
|
LL | fn from_iter<T: for<'x> LendingIterator<Item<'x> = A>>(iter: T) -> Self;
| ------------------------------------------------------------------------ definition of `from_iter` from trait

12
tests/ui/generic-associated-types/gat-in-trait-path.rs
View file

@ -1,10 +1,6 @@
//@ revisions: base extended
//@[base] check-fail
//@[extended] check-pass
//@ check-fail
#![feature(associated_type_defaults)]
#![cfg_attr(extended, feature(generic_associated_types_extended))]
#![cfg_attr(extended, allow(incomplete_features))]
trait Foo {
type A<'a> where Self: 'a;
@ -24,12 +20,12 @@ impl<T> Foo for Fooer<T> {
}
fn f(_arg : Box<dyn for<'a> Foo<A<'a> = &'a ()>>) {}
//[base]~^ the trait `Foo` cannot be made into an object
//~^ the trait `Foo` cannot be made into an object
fn main() {
let foo = Fooer(5);
f(Box::new(foo));
//[base]~^ the trait `Foo` cannot be made into an object
//[base]~| the trait `Foo` cannot be made into an object
//~^ the trait `Foo` cannot be made into an object
//~| the trait `Foo` cannot be made into an object
}

58
tests/ui/generic-associated-types/gat-in-trait-path.stderr Normal file
View file

@ -0,0 +1,58 @@
error[E0038]: the trait `Foo` cannot be made into an object
--> $DIR/gat-in-trait-path.rs:22:17
|
LL | fn f(_arg : Box<dyn for<'a> Foo<A<'a> = &'a ()>>) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `Foo` cannot be made into an object
|
note: for a trait to be "dyn-compatible" 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>
--> $DIR/gat-in-trait-path.rs:6:10
|
LL | trait Foo {
| --- this trait cannot be made into an object...
LL | type A<'a> where Self: 'a;
| ^ ...because it contains the generic associated type `A`
= help: consider moving `A` to another trait
= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `Foo` for this new enum and using it instead:
Fooy
Fooer<T>
error[E0038]: the trait `Foo` cannot be made into an object
--> $DIR/gat-in-trait-path.rs:28:5
|
LL | f(Box::new(foo));
| ^^^^^^^^^^^^^ `Foo` cannot be made into an object
|
note: for a trait to be "dyn-compatible" 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>
--> $DIR/gat-in-trait-path.rs:6:10
|
LL | trait Foo {
| --- this trait cannot be made into an object...
LL | type A<'a> where Self: 'a;
| ^ ...because it contains the generic associated type `A`
= help: consider moving `A` to another trait
= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `Foo` for this new enum and using it instead:
Fooy
Fooer<T>
error[E0038]: the trait `Foo` cannot be made into an object
--> $DIR/gat-in-trait-path.rs:28:5
|
LL | f(Box::new(foo));
| ^^^^^^^^^^^^^ `Foo` cannot be made into an object
|
note: for a trait to be "dyn-compatible" 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>
--> $DIR/gat-in-trait-path.rs:6:10
|
LL | trait Foo {
| --- this trait cannot be made into an object...
LL | type A<'a> where Self: 'a;
| ^ ...because it contains the generic associated type `A`
= help: consider moving `A` to another trait
= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `Foo` for this new enum and using it instead:
Fooy
Fooer<T>
= note: required for the cast from `Box<Fooer<{integer}>>` to `Box<(dyn Foo<A<'a> = &'a ()> + 'static)>`
error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0038`.

9
tests/ui/generic-associated-types/issue-67510-pass.rs
View file

@ -1,15 +1,10 @@
//@ revisions: base extended
//@[base] check-fail
//@[extended] check-pass
#![cfg_attr(extended, feature(generic_associated_types_extended))]
#![cfg_attr(extended, allow(incomplete_features))]
//@ check-fail
trait X {
type Y<'a>;
}
fn _func1<'a>(_x: Box<dyn X<Y<'a>=&'a ()>>) {}
//[base]~^ ERROR the trait `X` cannot be made into an object
//~^ ERROR the trait `X` cannot be made into an object
fn main() {}

18
tests/ui/generic-associated-types/issue-67510-pass.stderr Normal file
View file

@ -0,0 +1,18 @@
error[E0038]: the trait `X` cannot be made into an object
--> $DIR/issue-67510-pass.rs:7:23
|
LL | fn _func1<'a>(_x: Box<dyn X<Y<'a>=&'a ()>>) {}
| ^^^^^^^^^^^^^^^^^^^ `X` cannot be made into an object
|
note: for a trait to be "dyn-compatible" 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>
--> $DIR/issue-67510-pass.rs:4:10
|
LL | trait X {
| - this trait cannot be made into an object...
LL | type Y<'a>;
| ^ ...because it contains the generic associated type `Y`
= help: consider moving `Y` to another trait
error: aborting due to 1 previous error
For more information about this error, try `rustc --explain E0038`.

9
tests/ui/generic-associated-types/issue-76535.rs
View file

@ -1,8 +1,3 @@
//@ revisions: base extended
#![cfg_attr(extended, feature(generic_associated_types_extended))]
#![cfg_attr(extended, allow(incomplete_features))]
pub trait SubTrait {}
pub trait SuperTrait {
@ -38,6 +33,6 @@ impl SuperTrait for SuperStruct {
fn main() {
let sub: Box<dyn SuperTrait<SubType = SubStruct>> = Box::new(SuperStruct::new(0));
//~^ ERROR missing generics for associated type
//[base]~^^ ERROR the trait
//[base]~| ERROR the trait
//~^^ ERROR the trait
//~| ERROR the trait
}

55
tests/ui/generic-associated-types/issue-76535.stderr Normal file
View file

@ -0,0 +1,55 @@
error[E0107]: missing generics for associated type `SuperTrait::SubType`
--> $DIR/issue-76535.rs:34:33
|
LL | let sub: Box<dyn SuperTrait<SubType = SubStruct>> = Box::new(SuperStruct::new(0));
| ^^^^^^^ expected 1 lifetime argument
|
note: associated type defined here, with 1 lifetime parameter: `'a`
--> $DIR/issue-76535.rs:4:10
|
LL | type SubType<'a>: SubTrait where Self: 'a;
| ^^^^^^^ --
help: add missing lifetime argument
|
LL | let sub: Box<dyn SuperTrait<SubType<'a> = SubStruct>> = Box::new(SuperStruct::new(0));
| ++++
error[E0038]: the trait `SuperTrait` cannot be made into an object
--> $DIR/issue-76535.rs:34:14
|
LL | let sub: Box<dyn SuperTrait<SubType = SubStruct>> = Box::new(SuperStruct::new(0));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `SuperTrait` cannot be made into an object
|
note: for a trait to be "dyn-compatible" 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>
--> $DIR/issue-76535.rs:4:10
|
LL | pub trait SuperTrait {
| ---------- this trait cannot be made into an object...
LL | type SubType<'a>: SubTrait where Self: 'a;
| ^^^^^^^ ...because it contains the generic associated type `SubType`
= help: consider moving `SubType` to another trait
= help: only type `SuperStruct` is seen to implement the trait in this crate, consider using it directly instead
= note: `SuperTrait` can be implemented in other crates; if you want to support your users passing their own types here, you can't refer to a specific type
error[E0038]: the trait `SuperTrait` cannot be made into an object
--> $DIR/issue-76535.rs:34:57
|
LL | let sub: Box<dyn SuperTrait<SubType = SubStruct>> = Box::new(SuperStruct::new(0));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `SuperTrait` cannot be made into an object
|
note: for a trait to be "dyn-compatible" 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>
--> $DIR/issue-76535.rs:4:10
|
LL | pub trait SuperTrait {
| ---------- this trait cannot be made into an object...
LL | type SubType<'a>: SubTrait where Self: 'a;
| ^^^^^^^ ...because it contains the generic associated type `SubType`
= help: consider moving `SubType` to another trait
= help: only type `SuperStruct` is seen to implement the trait in this crate, consider using it directly instead
= note: `SuperTrait` can be implemented in other crates; if you want to support your users passing their own types here, you can't refer to a specific type
= note: required for the cast from `Box<SuperStruct>` to `Box<dyn SuperTrait<SubType<'_> = SubStruct<'_>>>`
error: aborting due to 3 previous errors
Some errors have detailed explanations: E0038, E0107.
For more information about an error, try `rustc --explain E0038`.

7
tests/ui/generic-associated-types/issue-78671.rs
View file

@ -1,15 +1,10 @@
//@ revisions: base extended
#![cfg_attr(extended, feature(generic_associated_types_extended))]
#![cfg_attr(extended, allow(incomplete_features))]
trait CollectionFamily {
type Member<T>;
}
fn floatify() {
Box::new(Family) as &dyn CollectionFamily<Member=usize>
//~^ ERROR: missing generics for associated type
//[base]~^^ ERROR: the trait `CollectionFamily` cannot be made into an object
//~| ERROR: the trait `CollectionFamily` cannot be made into an object
}
struct Family;

35
tests/ui/generic-associated-types/issue-78671.stderr Normal file
View file

@ -0,0 +1,35 @@
error[E0107]: missing generics for associated type `CollectionFamily::Member`
--> $DIR/issue-78671.rs:5:47
|
LL | Box::new(Family) as &dyn CollectionFamily<Member=usize>
| ^^^^^^ expected 1 generic argument
|
note: associated type defined here, with 1 generic parameter: `T`
--> $DIR/issue-78671.rs:2:10
|
LL | type Member<T>;
| ^^^^^^ -
help: add missing generic argument
|
LL | Box::new(Family) as &dyn CollectionFamily<Member<T>=usize>
| +++
error[E0038]: the trait `CollectionFamily` cannot be made into an object
--> $DIR/issue-78671.rs:5:25
|
LL | Box::new(Family) as &dyn CollectionFamily<Member=usize>
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `CollectionFamily` cannot be made into an object
|
note: for a trait to be "dyn-compatible" 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>
--> $DIR/issue-78671.rs:2:10
|
LL | trait CollectionFamily {
| ---------------- this trait cannot be made into an object...
LL | type Member<T>;
| ^^^^^^ ...because it contains the generic associated type `Member`
= help: consider moving `Member` to another trait
error: aborting due to 2 previous errors
Some errors have detailed explanations: E0038, E0107.
For more information about an error, try `rustc --explain E0038`.

10
tests/ui/generic-associated-types/issue-79422.rs
View file

@ -1,8 +1,3 @@
//@ revisions: base extended
#![cfg_attr(extended, feature(generic_associated_types_extended))]
#![cfg_attr(extended, allow(incomplete_features))]
trait RefCont<'a, T> {
fn t(&'a self) -> &'a T;
}
@ -42,9 +37,8 @@ impl<K, V: Default> MapLike<K, V> for Source {
fn main() {
let m = Box::new(std::collections::BTreeMap::<u8, u8>::new())
//[base]~^ ERROR the trait
//[extended]~^^ type mismatch
//~^ ERROR the trait
as Box<dyn MapLike<u8, u8, VRefCont = dyn RefCont<'_, u8>>>;
//~^ ERROR missing generics for associated type
//[base]~^^ ERROR the trait
//~| ERROR the trait
}

57
tests/ui/generic-associated-types/issue-79422.stderr Normal file
View file

@ -0,0 +1,57 @@
error[E0107]: missing generics for associated type `MapLike::VRefCont`
--> $DIR/issue-79422.rs:41:36
|
LL | as Box<dyn MapLike<u8, u8, VRefCont = dyn RefCont<'_, u8>>>;
| ^^^^^^^^ expected 1 lifetime argument
|
note: associated type defined here, with 1 lifetime parameter: `'a`
--> $DIR/issue-79422.rs:18:10
|
LL | type VRefCont<'a>: RefCont<'a, V> where Self: 'a;
| ^^^^^^^^ --
help: add missing lifetime argument
|
LL | as Box<dyn MapLike<u8, u8, VRefCont<'a> = dyn RefCont<'_, u8>>>;
| ++++
error[E0038]: the trait `MapLike` cannot be made into an object
--> $DIR/issue-79422.rs:41:12
|
LL | as Box<dyn MapLike<u8, u8, VRefCont = dyn RefCont<'_, u8>>>;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `MapLike` cannot be made into an object
|
note: for a trait to be "dyn-compatible" 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>
--> $DIR/issue-79422.rs:18:10
|
LL | trait MapLike<K, V> {
| ------- this trait cannot be made into an object...
LL | type VRefCont<'a>: RefCont<'a, V> where Self: 'a;
| ^^^^^^^^ ...because it contains the generic associated type `VRefCont`
= help: consider moving `VRefCont` to another trait
= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `MapLike` for this new enum and using it instead:
std::collections::BTreeMap<K, V>
Source
error[E0038]: the trait `MapLike` cannot be made into an object
--> $DIR/issue-79422.rs:39:13
|
LL | let m = Box::new(std::collections::BTreeMap::<u8, u8>::new())
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `MapLike` cannot be made into an object
|
note: for a trait to be "dyn-compatible" 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>
--> $DIR/issue-79422.rs:18:10
|
LL | trait MapLike<K, V> {
| ------- this trait cannot be made into an object...
LL | type VRefCont<'a>: RefCont<'a, V> where Self: 'a;
| ^^^^^^^^ ...because it contains the generic associated type `VRefCont`
= help: consider moving `VRefCont` to another trait
= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `MapLike` for this new enum and using it instead:
std::collections::BTreeMap<K, V>
Source
= note: required for the cast from `Box<BTreeMap<u8, u8>>` to `Box<dyn MapLike<u8, u8, VRefCont<'_> = (dyn RefCont<'_, u8> + 'static)>>`
error: aborting due to 3 previous errors
Some errors have detailed explanations: E0038, E0107.
For more information about an error, try `rustc --explain E0038`.

12
tests/ui/generic-associated-types/trait-objects.rs
View file

@ -1,8 +1,3 @@
//@ revisions: base extended
#![cfg_attr(extended, feature(generic_associated_types_extended))]
#![cfg_attr(extended, allow(incomplete_features))]
trait StreamingIterator {
type Item<'a> where Self: 'a;
fn size_hint(&self) -> (usize, Option<usize>);
@ -11,11 +6,10 @@ trait StreamingIterator {
}
fn min_size(x: &mut dyn for<'a> StreamingIterator<Item<'a> = &'a i32>) -> usize {
//[base]~^ the trait `StreamingIterator` cannot be made into an object
//~^ the trait `StreamingIterator` cannot be made into an object
x.size_hint().0
//[extended]~^ borrowed data escapes
//[base]~^^ the trait `StreamingIterator` cannot be made into an object
//[base]~| the trait `StreamingIterator` cannot be made into an object
//~^ the trait `StreamingIterator` cannot be made into an object
//~| the trait `StreamingIterator` cannot be made into an object
}
fn main() {}

48
tests/ui/generic-associated-types/trait-objects.stderr Normal file
View file

@ -0,0 +1,48 @@
error[E0038]: the trait `StreamingIterator` cannot be made into an object
--> $DIR/trait-objects.rs:8:21
|
LL | fn min_size(x: &mut dyn for<'a> StreamingIterator<Item<'a> = &'a i32>) -> usize {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `StreamingIterator` cannot be made into an object
|
note: for a trait to be "dyn-compatible" 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>
--> $DIR/trait-objects.rs:2:10
|
LL | trait StreamingIterator {
| ----------------- this trait cannot be made into an object...
LL | type Item<'a> where Self: 'a;
| ^^^^ ...because it contains the generic associated type `Item`
= help: consider moving `Item` to another trait
error[E0038]: the trait `StreamingIterator` cannot be made into an object
--> $DIR/trait-objects.rs:10:7
|
LL | x.size_hint().0
| ^^^^^^^^^ `StreamingIterator` cannot be made into an object
|
note: for a trait to be "dyn-compatible" 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>
--> $DIR/trait-objects.rs:2:10
|
LL | trait StreamingIterator {
| ----------------- this trait cannot be made into an object...
LL | type Item<'a> where Self: 'a;
| ^^^^ ...because it contains the generic associated type `Item`
= help: consider moving `Item` to another trait
error[E0038]: the trait `StreamingIterator` cannot be made into an object
--> $DIR/trait-objects.rs:10:5
|
LL | x.size_hint().0
| ^^^^^^^^^^^^^ `StreamingIterator` cannot be made into an object
|
note: for a trait to be "dyn-compatible" 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>
--> $DIR/trait-objects.rs:2:10
|
LL | trait StreamingIterator {
| ----------------- this trait cannot be made into an object...
LL | type Item<'a> where Self: 'a;
| ^^^^ ...because it contains the generic associated type `Item`
= help: consider moving `Item` to another trait
error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0038`.