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Rollup merge of #119752 - estebank:ice-ice, r=fmease 

Avoid ICEs in trait names without `dyn`

Check diagnostic is error before downgrading. Fix #119633.

 Account for traits using self-trait by name without `dyn`. Fix #119652.
This commit is contained in:
Matthias Krüger 2024-01-20 09:37:27 +01:00 committed by GitHub
parent 2de5ca25d2 7edbc95c27
commit 177d51372c
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
11 changed files with 553 additions and 11 deletions
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32
compiler/rustc_hir_analysis/src/astconv/lint.rs
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@ -78,14 +78,17 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
fn maybe_lint_impl_trait(&self, self_ty: &hir::Ty<'_>, diag: &mut Diagnostic) -> bool {
let tcx = self.tcx();
let parent_id = tcx.hir().get_parent_item(self_ty.hir_id).def_id;
let (hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(sig, generics, _), .. })
| hir::Node::TraitItem(hir::TraitItem {
kind: hir::TraitItemKind::Fn(sig, _),
generics,
..
})) = tcx.hir_node_by_def_id(parent_id)
else {
return false;
let (sig, generics, owner) = match tcx.hir_node_by_def_id(parent_id) {
hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(sig, generics, _), .. }) => {
(sig, generics, None)
}
hir::Node::TraitItem(hir::TraitItem {
kind: hir::TraitItemKind::Fn(sig, _),
generics,
owner_id,
..
}) => (sig, generics, Some(tcx.parent(owner_id.to_def_id()))),
_ => return false,
};
let Ok(trait_name) = tcx.sess.source_map().span_to_snippet(self_ty.span) else {
return false;
@ -94,6 +97,11 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
let is_object_safe = match self_ty.kind {
hir::TyKind::TraitObject(objects, ..) => {
objects.iter().all(|o| match o.trait_ref.path.res {
Res::Def(DefKind::Trait, id) if Some(id) == owner => {
// When we're dealing with a recursive trait, we don't want to downgrade
// the error, so we consider them to be object safe always. (#119652)
true
}
Res::Def(DefKind::Trait, id) => tcx.check_is_object_safe(id),
_ => false,
})
@ -122,7 +130,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
],
Applicability::MachineApplicable,
);
} else {
} else if diag.is_error() {
// We'll emit the object safety error already, with a structured suggestion.
diag.downgrade_to_delayed_bug();
}
@ -148,8 +156,10 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
}
if !is_object_safe {
diag.note(format!("`{trait_name}` it is not object safe, so it can't be `dyn`"));
// We'll emit the object safety error already, with a structured suggestion.
diag.downgrade_to_delayed_bug();
if diag.is_error() {
// We'll emit the object safety error already, with a structured suggestion.
diag.downgrade_to_delayed_bug();
}
} else {
let sugg = if let hir::TyKind::TraitObject([_, _, ..], _, _) = self_ty.kind {
// There are more than one trait bound, we need surrounding parentheses.

9
tests/ui/object-safety/avoid-ice-on-warning-2.rs Normal file
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@ -0,0 +1,9 @@
fn id<F>(f: Copy) -> usize {
//~^ WARN trait objects without an explicit `dyn` are deprecated
//~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
//~| WARN trait objects without an explicit `dyn` are deprecated
//~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
//~| ERROR the trait `Copy` cannot be made into an object
f()
}
fn main() {}

50
tests/ui/object-safety/avoid-ice-on-warning-2.stderr Normal file
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@ -0,0 +1,50 @@
warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning-2.rs:1:13
|
LL | fn id<F>(f: Copy) -> usize {
| ^^^^
|
= warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
= note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
= note: `Copy` it is not object safe, so it can't be `dyn`
= note: `#[warn(bare_trait_objects)]` on by default
help: use a new generic type parameter, constrained by `Copy`
|
LL | fn id<F, T: Copy>(f: T) -> usize {
| +++++++++ ~
help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference
|
LL | fn id<F>(f: impl Copy) -> usize {
| ++++
warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning-2.rs:1:13
|
LL | fn id<F>(f: Copy) -> usize {
| ^^^^
|
= warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
= note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
= note: `Copy` it is not object safe, so it can't be `dyn`
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
help: use a new generic type parameter, constrained by `Copy`
|
LL | fn id<F, T: Copy>(f: T) -> usize {
| +++++++++ ~
help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference
|
LL | fn id<F>(f: impl Copy) -> usize {
| ++++
error[E0038]: the trait `Copy` cannot be made into an object
--> $DIR/avoid-ice-on-warning-2.rs:1:13
|
LL | fn id<F>(f: Copy) -> usize {
| ^^^^ `Copy` cannot be made into an object
|
= note: the trait cannot be made into an object because it requires `Self: Sized`
= 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>
error: aborting due to 1 previous error; 2 warnings emitted
For more information about this error, try `rustc --explain E0038`.

17
tests/ui/object-safety/avoid-ice-on-warning-3.rs Normal file
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@ -0,0 +1,17 @@
trait B { fn f(a: A) -> A; }
//~^ WARN trait objects without an explicit `dyn` are deprecated
//~| WARN trait objects without an explicit `dyn` are deprecated
//~| WARN trait objects without an explicit `dyn` are deprecated
//~| WARN this is accepted in the current edition
//~| WARN this is accepted in the current edition
//~| WARN this is accepted in the current edition
//~| ERROR the trait `A` cannot be made into an object
trait A { fn g(b: B) -> B; }
//~^ WARN trait objects without an explicit `dyn` are deprecated
//~| WARN trait objects without an explicit `dyn` are deprecated
//~| WARN trait objects without an explicit `dyn` are deprecated
//~| WARN this is accepted in the current edition
//~| WARN this is accepted in the current edition
//~| WARN this is accepted in the current edition
//~| ERROR the trait `B` cannot be made into an object
fn main() {}

148
tests/ui/object-safety/avoid-ice-on-warning-3.stderr Normal file
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@ -0,0 +1,148 @@
warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning-3.rs:9:19
|
LL | trait A { fn g(b: B) -> B; }
| ^
|
= warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
= note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
= note: `B` it is not object safe, so it can't be `dyn`
= note: `#[warn(bare_trait_objects)]` on by default
help: use a new generic type parameter, constrained by `B`
|
LL | trait A { fn g<T: B>(b: T) -> B; }
| ++++++ ~
help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference
|
LL | trait A { fn g(b: impl B) -> B; }
| ++++
warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning-3.rs:9:25
|
LL | trait A { fn g(b: B) -> B; }
| ^
|
= warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
= note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
help: `B` is not object safe, use `impl B` to return an opaque type, as long as you return a single underlying type
|
LL | trait A { fn g(b: B) -> impl B; }
| ++++
warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning-3.rs:1:19
|
LL | trait B { fn f(a: A) -> A; }
| ^
|
= warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
= note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
= note: `A` it is not object safe, so it can't be `dyn`
help: use a new generic type parameter, constrained by `A`
|
LL | trait B { fn f<T: A>(a: T) -> A; }
| ++++++ ~
help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference
|
LL | trait B { fn f(a: impl A) -> A; }
| ++++
warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning-3.rs:1:25
|
LL | trait B { fn f(a: A) -> A; }
| ^
|
= warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
= note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
help: `A` is not object safe, use `impl A` to return an opaque type, as long as you return a single underlying type
|
LL | trait B { fn f(a: A) -> impl A; }
| ++++
warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning-3.rs:1:19
|
LL | trait B { fn f(a: A) -> A; }
| ^
|
= warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
= note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
= note: `A` it is not object safe, so it can't be `dyn`
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
help: use a new generic type parameter, constrained by `A`
|
LL | trait B { fn f<T: A>(a: T) -> A; }
| ++++++ ~
help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference
|
LL | trait B { fn f(a: impl A) -> A; }
| ++++
error[E0038]: the trait `A` cannot be made into an object
--> $DIR/avoid-ice-on-warning-3.rs:1:19
|
LL | trait B { fn f(a: A) -> A; }
| ^ `A` cannot be made into an object
|
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>
--> $DIR/avoid-ice-on-warning-3.rs:9:14
|
LL | trait A { fn g(b: B) -> B; }
| - ^ ...because associated function `g` has no `self` parameter
| |
| this trait cannot be made into an object...
help: consider turning `g` into a method by giving it a `&self` argument
|
LL | trait A { fn g(&self, b: B) -> B; }
| ++++++
help: alternatively, consider constraining `g` so it does not apply to trait objects
|
LL | trait A { fn g(b: B) -> B where Self: Sized; }
| +++++++++++++++++
warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning-3.rs:9:19
|
LL | trait A { fn g(b: B) -> B; }
| ^
|
= warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
= note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
= note: `B` it is not object safe, so it can't be `dyn`
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
help: use a new generic type parameter, constrained by `B`
|
LL | trait A { fn g<T: B>(b: T) -> B; }
| ++++++ ~
help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference
|
LL | trait A { fn g(b: impl B) -> B; }
| ++++
error[E0038]: the trait `B` cannot be made into an object
--> $DIR/avoid-ice-on-warning-3.rs:9:19
|
LL | trait A { fn g(b: B) -> B; }
| ^ `B` cannot be made into an object
|
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>
--> $DIR/avoid-ice-on-warning-3.rs:1:14
|
LL | trait B { fn f(a: A) -> A; }
| - ^ ...because associated function `f` has no `self` parameter
| |
| this trait cannot be made into an object...
help: consider turning `f` into a method by giving it a `&self` argument
|
LL | trait B { fn f(&self, a: A) -> A; }
| ++++++
help: alternatively, consider constraining `f` so it does not apply to trait objects
|
LL | trait B { fn f(a: A) -> A where Self: Sized; }
| +++++++++++++++++
error: aborting due to 2 previous errors; 6 warnings emitted
For more information about this error, try `rustc --explain E0038`.

6
tests/ui/object-safety/avoid-ice-on-warning.rs Normal file
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@ -0,0 +1,6 @@
fn call_this<F>(f: F) : Fn(&str) + call_that {}
//~^ ERROR return types are denoted using `->`
//~| ERROR cannot find trait `call_that` in this scope
//~| WARN trait objects without an explicit `dyn` are deprecated
//~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
fn main() {}

29
tests/ui/object-safety/avoid-ice-on-warning.stderr Normal file
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@ -0,0 +1,29 @@
error: return types are denoted using `->`
--> $DIR/avoid-ice-on-warning.rs:1:23
|
LL | fn call_this<F>(f: F) : Fn(&str) + call_that {}
| ^ help: use `->` instead
error[E0405]: cannot find trait `call_that` in this scope
--> $DIR/avoid-ice-on-warning.rs:1:36
|
LL | fn call_this<F>(f: F) : Fn(&str) + call_that {}
| ^^^^^^^^^ not found in this scope
warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning.rs:1:25
|
LL | fn call_this<F>(f: F) : Fn(&str) + call_that {}
| ^^^^^^^^^^^^^^^^^^^^
|
= warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
= note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
= note: `#[warn(bare_trait_objects)]` on by default
help: `Fn(&str) + call_that` is not object safe, use `impl Fn(&str) + call_that` to return an opaque type, as long as you return a single underlying type
|
LL | fn call_this<F>(f: F) : impl Fn(&str) + call_that {}
| ++++
error: aborting due to 2 previous errors; 1 warning emitted
For more information about this error, try `rustc --explain E0405`.

23
tests/ui/suggestions/object-unsafe-trait-should-use-self-2021-without-dyn.rs Normal file
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@ -0,0 +1,23 @@
// edition:2021
#![allow(bare_trait_objects)]
trait A: Sized {
fn f(a: A) -> A;
//~^ ERROR trait objects must include the `dyn` keyword
//~| ERROR trait objects must include the `dyn` keyword
//~| ERROR associated item referring to unboxed trait object for its own trait
//~| ERROR the trait `A` cannot be made into an object
}
trait B {
fn f(a: B) -> B;
//~^ ERROR trait objects must include the `dyn` keyword
//~| ERROR trait objects must include the `dyn` keyword
//~| ERROR associated item referring to unboxed trait object for its own trait
//~| ERROR the trait `B` cannot be made into an object
}
trait C {
fn f(&self, a: C) -> C;
//~^ ERROR trait objects must include the `dyn` keyword
//~| ERROR trait objects must include the `dyn` keyword
}
fn main() {}

168
tests/ui/suggestions/object-unsafe-trait-should-use-self-2021-without-dyn.stderr Normal file
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@ -0,0 +1,168 @@
error: associated item referring to unboxed trait object for its own trait
--> $DIR/object-unsafe-trait-should-use-self-2021-without-dyn.rs:4:13
|
LL | trait A: Sized {
| - in this trait
LL | fn f(a: A) -> A;
| ^ ^
|
help: you might have meant to use `Self` to refer to the implementing type
|
LL | fn f(a: Self) -> Self;
| ~~~~ ~~~~
error[E0038]: the trait `A` cannot be made into an object
--> $DIR/object-unsafe-trait-should-use-self-2021-without-dyn.rs:4:13
|
LL | fn f(a: A) -> A;
| ^ `A` cannot be made into an object
|
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>
--> $DIR/object-unsafe-trait-should-use-self-2021-without-dyn.rs:3:10
|
LL | trait A: Sized {
| - ^^^^^ ...because it requires `Self: Sized`
| |
| this trait cannot be made into an object...
error: associated item referring to unboxed trait object for its own trait
--> $DIR/object-unsafe-trait-should-use-self-2021-without-dyn.rs:11:13
|
LL | trait B {
| - in this trait
LL | fn f(a: B) -> B;
| ^ ^
|
help: you might have meant to use `Self` to refer to the implementing type
|
LL | fn f(a: Self) -> Self;
| ~~~~ ~~~~
error[E0038]: the trait `B` cannot be made into an object
--> $DIR/object-unsafe-trait-should-use-self-2021-without-dyn.rs:11:13
|
LL | fn f(a: B) -> B;
| ^ `B` cannot be made into an object
|
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>
--> $DIR/object-unsafe-trait-should-use-self-2021-without-dyn.rs:11:8
|
LL | trait B {
| - this trait cannot be made into an object...
LL | fn f(a: B) -> B;
| ^ ...because associated function `f` has no `self` parameter
help: consider turning `f` into a method by giving it a `&self` argument
|
LL | fn f(&self, a: B) -> B;
| ++++++
help: alternatively, consider constraining `f` so it does not apply to trait objects
|
LL | fn f(a: B) -> B where Self: Sized;
| +++++++++++++++++
error[E0782]: trait objects must include the `dyn` keyword
--> $DIR/object-unsafe-trait-should-use-self-2021-without-dyn.rs:4:13
|
LL | fn f(a: A) -> A;
| ^
|
help: use a new generic type parameter, constrained by `A`
|
LL | fn f<T: A>(a: T) -> A;
| ++++++ ~
help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference
|
LL | fn f(a: impl A) -> A;
| ++++
help: alternatively, use a trait object to accept any type that implements `A`, accessing its methods at runtime using dynamic dispatch
|
LL | fn f(a: &dyn A) -> A;
| ++++
error[E0782]: trait objects must include the `dyn` keyword
--> $DIR/object-unsafe-trait-should-use-self-2021-without-dyn.rs:4:19
|
LL | fn f(a: A) -> A;
| ^
|
help: use `impl A` to return an opaque type, as long as you return a single underlying type
|
LL | fn f(a: A) -> impl A;
| ++++
help: alternatively, you can return an owned trait object
|
LL | fn f(a: A) -> Box<dyn A>;
| +++++++ +
error[E0782]: trait objects must include the `dyn` keyword
--> $DIR/object-unsafe-trait-should-use-self-2021-without-dyn.rs:11:13
|
LL | fn f(a: B) -> B;
| ^
|
help: use a new generic type parameter, constrained by `B`
|
LL | fn f<T: B>(a: T) -> B;
| ++++++ ~
help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference
|
LL | fn f(a: impl B) -> B;
| ++++
help: alternatively, use a trait object to accept any type that implements `B`, accessing its methods at runtime using dynamic dispatch
|
LL | fn f(a: &dyn B) -> B;
| ++++
error[E0782]: trait objects must include the `dyn` keyword
--> $DIR/object-unsafe-trait-should-use-self-2021-without-dyn.rs:11:19
|
LL | fn f(a: B) -> B;
| ^
|
help: use `impl B` to return an opaque type, as long as you return a single underlying type
|
LL | fn f(a: B) -> impl B;
| ++++
help: alternatively, you can return an owned trait object
|
LL | fn f(a: B) -> Box<dyn B>;
| +++++++ +
error[E0782]: trait objects must include the `dyn` keyword
--> $DIR/object-unsafe-trait-should-use-self-2021-without-dyn.rs:18:20
|
LL | fn f(&self, a: C) -> C;
| ^
|
help: use a new generic type parameter, constrained by `C`
|
LL | fn f<T: C>(&self, a: T) -> C;
| ++++++ ~
help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference
|
LL | fn f(&self, a: impl C) -> C;
| ++++
help: alternatively, use a trait object to accept any type that implements `C`, accessing its methods at runtime using dynamic dispatch
|
LL | fn f(&self, a: &dyn C) -> C;
| ++++
error[E0782]: trait objects must include the `dyn` keyword
--> $DIR/object-unsafe-trait-should-use-self-2021-without-dyn.rs:18:26
|
LL | fn f(&self, a: C) -> C;
| ^
|
help: use `impl C` to return an opaque type, as long as you return a single underlying type
|
LL | fn f(&self, a: C) -> impl C;
| ++++
help: alternatively, you can return an owned trait object
|
LL | fn f(&self, a: C) -> Box<dyn C>;
| +++++++ +
error: aborting due to 10 previous errors
Some errors have detailed explanations: E0038, E0782.
For more information about an error, try `rustc --explain E0038`.

17
tests/ui/suggestions/object-unsafe-trait-should-use-self-2021.rs Normal file
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@ -0,0 +1,17 @@
// edition:2021
#![allow(bare_trait_objects)]
trait A: Sized {
fn f(a: dyn A) -> dyn A;
//~^ ERROR associated item referring to unboxed trait object for its own trait
//~| ERROR the trait `A` cannot be made into an object
}
trait B {
fn f(a: dyn B) -> dyn B;
//~^ ERROR associated item referring to unboxed trait object for its own trait
//~| ERROR the trait `B` cannot be made into an object
}
trait C {
fn f(&self, a: dyn C) -> dyn C;
}
fn main() {}

65
tests/ui/suggestions/object-unsafe-trait-should-use-self-2021.stderr Normal file
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@ -0,0 +1,65 @@
error: associated item referring to unboxed trait object for its own trait
--> $DIR/object-unsafe-trait-should-use-self-2021.rs:4:13
|
LL | trait A: Sized {
| - in this trait
LL | fn f(a: dyn A) -> dyn A;
| ^^^^^ ^^^^^
|
help: you might have meant to use `Self` to refer to the implementing type
|
LL | fn f(a: Self) -> Self;
| ~~~~ ~~~~
error[E0038]: the trait `A` cannot be made into an object
--> $DIR/object-unsafe-trait-should-use-self-2021.rs:4:13
|
LL | fn f(a: dyn A) -> dyn A;
| ^^^^^ `A` cannot be made into an object
|
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>
--> $DIR/object-unsafe-trait-should-use-self-2021.rs:3:10
|
LL | trait A: Sized {
| - ^^^^^ ...because it requires `Self: Sized`
| |
| this trait cannot be made into an object...
error: associated item referring to unboxed trait object for its own trait
--> $DIR/object-unsafe-trait-should-use-self-2021.rs:9:13
|
LL | trait B {
| - in this trait
LL | fn f(a: dyn B) -> dyn B;
| ^^^^^ ^^^^^
|
help: you might have meant to use `Self` to refer to the implementing type
|
LL | fn f(a: Self) -> Self;
| ~~~~ ~~~~
error[E0038]: the trait `B` cannot be made into an object
--> $DIR/object-unsafe-trait-should-use-self-2021.rs:9:13
|
LL | fn f(a: dyn B) -> dyn B;
| ^^^^^ `B` cannot be made into an object
|
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>
--> $DIR/object-unsafe-trait-should-use-self-2021.rs:9:8
|
LL | trait B {
| - this trait cannot be made into an object...
LL | fn f(a: dyn B) -> dyn B;
| ^ ...because associated function `f` has no `self` parameter
help: consider turning `f` into a method by giving it a `&self` argument
|
LL | fn f(&self, a: dyn B) -> dyn B;
| ++++++
help: alternatively, consider constraining `f` so it does not apply to trait objects
|
LL | fn f(a: dyn B) -> dyn B where Self: Sized;
| +++++++++++++++++
error: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0038`.