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Reword diagnostics about relaxed bounds in invalid contexts

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This commit is contained in:
León Orell Valerian Liehr
2025-06-20 21:39:19 +02:00
parent 1df99f22d3
commit 84ed70b69d
19 changed files with 125 additions and 240 deletions
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26
compiler/rustc_ast_lowering/src/lib.rs
View File

@@ -60,7 +60,7 @@ use rustc_index::{Idx, IndexSlice, IndexVec};
use rustc_macros::extension; use rustc_macros::extension;
use rustc_middle::span_bug; use rustc_middle::span_bug;
use rustc_middle::ty::{ResolverAstLowering, TyCtxt}; use rustc_middle::ty::{ResolverAstLowering, TyCtxt};
use rustc_session::parse::{add_feature_diagnostics, feature_err}; use rustc_session::parse::add_feature_diagnostics;
use rustc_span::symbol::{Ident, Symbol, kw, sym}; use rustc_span::symbol::{Ident, Symbol, kw, sym};
use rustc_span::{DUMMY_SP, DesugaringKind, Span}; use rustc_span::{DUMMY_SP, DesugaringKind, Span};
use smallvec::SmallVec; use smallvec::SmallVec;
@@ -2071,7 +2071,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
span: Span, span: Span,
rbp: RelaxedBoundPolicy<'_>, rbp: RelaxedBoundPolicy<'_>,
) { ) {
let err = |message| feature_err(&self.tcx.sess, sym::more_maybe_bounds, span, message); // Even though feature `more_maybe_bounds` bypasses the given policy and (currently) enables
// relaxed bounds in every conceivable position[^1], we don't want to advertise it to the user
// (via a feature gate) since it's super internal. Besides this, it'd be quite distracting.
//
// [^1]: Strictly speaking, this is incorrect (at the very least for `Sized`) because it's
// no longer fully consistent with default trait elaboration in HIR ty lowering.
match rbp { match rbp {
RelaxedBoundPolicy::Allowed => return, RelaxedBoundPolicy::Allowed => return,
@@ -2093,11 +2098,17 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
match reason { match reason {
RelaxedBoundForbiddenReason::TraitObjectTy => { RelaxedBoundForbiddenReason::TraitObjectTy => {
err("`?Trait` is not permitted in trait object types").emit(); self.dcx().span_err(
span,
"relaxed bounds are not permitted in trait object types",
);
return; return;
} }
RelaxedBoundForbiddenReason::SuperTrait => { RelaxedBoundForbiddenReason::SuperTrait => {
let mut diag = err("`?Trait` is not permitted in supertraits"); let mut diag = self.dcx().struct_span_err(
span,
"relaxed bounds are not permitted in supertrait bounds",
);
if let Some(def_id) = trait_ref.trait_def_id() if let Some(def_id) = trait_ref.trait_def_id()
&& self.tcx.is_lang_item(def_id, hir::LangItem::Sized) && self.tcx.is_lang_item(def_id, hir::LangItem::Sized)
{ {
@@ -2111,7 +2122,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
} }
} }
err("`?Trait` bounds are only permitted at the point where a type parameter is declared") self.dcx()
.struct_span_err(span, "this relaxed bound is not permitted here")
.with_note(
"in this context, relaxed bounds are only allowed on \
type parameters defined by the closest item",
)
.emit(); .emit();
} }

2
tests/ui/associated-item/missing-associated_item_or_field_def_ids.rs
View File

@@ -2,6 +2,6 @@
fn main() -> dyn Iterator + ?Iterator::advance_by(usize) { fn main() -> dyn Iterator + ?Iterator::advance_by(usize) {
//~^ ERROR expected trait, found associated function `Iterator::advance_by` //~^ ERROR expected trait, found associated function `Iterator::advance_by`
//~| ERROR `?Trait` is not permitted in trait object types //~| ERROR relaxed bounds are not permitted in trait object types
todo!() todo!()
} }

8
tests/ui/associated-item/missing-associated_item_or_field_def_ids.stderr
View File

@@ -4,16 +4,12 @@ error[E0404]: expected trait, found associated function `Iterator::advance_by`
LL | fn main() -> dyn Iterator + ?Iterator::advance_by(usize) { LL | fn main() -> dyn Iterator + ?Iterator::advance_by(usize) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ not a trait | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ not a trait
error[E0658]: `?Trait` is not permitted in trait object types error: relaxed bounds are not permitted in trait object types
--> $DIR/missing-associated_item_or_field_def_ids.rs:3:29 --> $DIR/missing-associated_item_or_field_def_ids.rs:3:29
| |
LL | fn main() -> dyn Iterator + ?Iterator::advance_by(usize) { LL | fn main() -> dyn Iterator + ?Iterator::advance_by(usize) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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 2 previous errors error: aborting due to 2 previous errors
Some errors have detailed explanations: E0404, E0658. For more information about this error, try `rustc --explain E0404`.
For more information about an error, try `rustc --explain E0404`.

2
tests/ui/associated-types/avoid-getting-associated-items-of-undefined-trait.rs
View File

@@ -7,5 +7,5 @@ trait Tr {
fn main() { fn main() {
let _: dyn Tr + ?Foo<Assoc = ()>; let _: dyn Tr + ?Foo<Assoc = ()>;
//~^ ERROR: cannot find trait `Foo` in this scope //~^ ERROR: cannot find trait `Foo` in this scope
//~| ERROR: `?Trait` is not permitted in trait object types //~| ERROR: relaxed bounds are not permitted in trait object types
} }

8
tests/ui/associated-types/avoid-getting-associated-items-of-undefined-trait.stderr
View File

@@ -4,16 +4,12 @@ error[E0405]: cannot find trait `Foo` in this scope
LL | let _: dyn Tr + ?Foo<Assoc = ()>; LL | let _: dyn Tr + ?Foo<Assoc = ()>;
| ^^^ not found in this scope | ^^^ not found in this scope
error[E0658]: `?Trait` is not permitted in trait object types error: relaxed bounds are not permitted in trait object types
--> $DIR/avoid-getting-associated-items-of-undefined-trait.rs:8:21 --> $DIR/avoid-getting-associated-items-of-undefined-trait.rs:8:21
| |
LL | let _: dyn Tr + ?Foo<Assoc = ()>; LL | let _: dyn Tr + ?Foo<Assoc = ()>;
| ^^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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 2 previous errors error: aborting due to 2 previous errors
Some errors have detailed explanations: E0405, E0658. For more information about this error, try `rustc --explain E0405`.
For more information about an error, try `rustc --explain E0405`.

8
tests/ui/feature-gates/feature-gate-more-maybe-bounds.rs
View File

@@ -2,13 +2,11 @@
trait Trait1 {} trait Trait1 {}
auto trait Trait2 {} auto trait Trait2 {}
trait Trait3: ?Trait1 {} trait Trait3: ?Trait1 {} //~ ERROR relaxed bounds are not permitted in supertrait bounds
//~^ ERROR `?Trait` is not permitted in supertraits trait Trait4 where Self: ?Trait1 {} //~ ERROR this relaxed bound is not permitted here
trait Trait4 where Self: ?Trait1 {}
//~^ ERROR ?Trait` bounds are only permitted at the point where a type parameter is declared
fn foo(_: Box<dyn Trait1 + ?Trait2>) {} fn foo(_: Box<dyn Trait1 + ?Trait2>) {}
//~^ ERROR `?Trait` is not permitted in trait object types //~^ ERROR relaxed bounds are not permitted in trait object types
fn bar<T: ?Trait1 + ?Trait2>(_: T) {} fn bar<T: ?Trait1 + ?Trait2>(_: T) {}
//~^ ERROR type parameter has more than one relaxed default bound, only one is supported //~^ ERROR type parameter has more than one relaxed default bound, only one is supported
//~| ERROR relaxing a default bound only does something for `?Sized`; all other traits are not bound by default //~| ERROR relaxing a default bound only does something for `?Sized`; all other traits are not bound by default

34
tests/ui/feature-gates/feature-gate-more-maybe-bounds.stderr
View File

@@ -1,32 +1,25 @@
error[E0658]: `?Trait` is not permitted in supertraits error: relaxed bounds are not permitted in supertrait bounds
--> $DIR/feature-gate-more-maybe-bounds.rs:5:15 --> $DIR/feature-gate-more-maybe-bounds.rs:5:15
| |
LL | trait Trait3: ?Trait1 {} LL | trait Trait3: ?Trait1 {}
| ^^^^^^^ | ^^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` bounds are only permitted at the point where a type parameter is declared error: this relaxed bound is not permitted here
--> $DIR/feature-gate-more-maybe-bounds.rs:7:26 --> $DIR/feature-gate-more-maybe-bounds.rs:6:26
| |
LL | trait Trait4 where Self: ?Trait1 {} LL | trait Trait4 where Self: ?Trait1 {}
| ^^^^^^^ | ^^^^^^^
| |
= help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable = note: in this context, relaxed bounds are only allowed on type parameters defined by the closest item
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error[E0658]: `?Trait` is not permitted in trait object types error: relaxed bounds are not permitted in trait object types
--> $DIR/feature-gate-more-maybe-bounds.rs:10:28 --> $DIR/feature-gate-more-maybe-bounds.rs:8:28
| |
LL | fn foo(_: Box<dyn Trait1 + ?Trait2>) {} LL | fn foo(_: Box<dyn Trait1 + ?Trait2>) {}
| ^^^^^^^ | ^^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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[E0203]: type parameter has more than one relaxed default bound, only one is supported error[E0203]: type parameter has more than one relaxed default bound, only one is supported
--> $DIR/feature-gate-more-maybe-bounds.rs:12:11 --> $DIR/feature-gate-more-maybe-bounds.rs:10:11
| |
LL | fn bar<T: ?Trait1 + ?Trait2>(_: T) {} LL | fn bar<T: ?Trait1 + ?Trait2>(_: T) {}
| ^^^^^^^ ^^^^^^^ | ^^^^^^^ ^^^^^^^
@@ -35,36 +28,35 @@ LL | fn bar<T: ?Trait1 + ?Trait2>(_: T) {}
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
--> $DIR/feature-gate-more-maybe-bounds.rs:12:11 --> $DIR/feature-gate-more-maybe-bounds.rs:10:11
| |
LL | fn bar<T: ?Trait1 + ?Trait2>(_: T) {} LL | fn bar<T: ?Trait1 + ?Trait2>(_: T) {}
| ^^^^^^^ | ^^^^^^^
error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
--> $DIR/feature-gate-more-maybe-bounds.rs:12:21 --> $DIR/feature-gate-more-maybe-bounds.rs:10:21
| |
LL | fn bar<T: ?Trait1 + ?Trait2>(_: T) {} LL | fn bar<T: ?Trait1 + ?Trait2>(_: T) {}
| ^^^^^^^ | ^^^^^^^
error[E0203]: type parameter has more than one relaxed default bound, only one is supported error[E0203]: type parameter has more than one relaxed default bound, only one is supported
--> $DIR/feature-gate-more-maybe-bounds.rs:19:11 --> $DIR/feature-gate-more-maybe-bounds.rs:17:11
| |
LL | fn baz<T: ?Trait + ?Trait>(_ : T) {} LL | fn baz<T: ?Trait + ?Trait>(_ : T) {}
| ^^^^^^ ^^^^^^ | ^^^^^^ ^^^^^^
error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
--> $DIR/feature-gate-more-maybe-bounds.rs:19:11 --> $DIR/feature-gate-more-maybe-bounds.rs:17:11
| |
LL | fn baz<T: ?Trait + ?Trait>(_ : T) {} LL | fn baz<T: ?Trait + ?Trait>(_ : T) {}
| ^^^^^^ | ^^^^^^
error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
--> $DIR/feature-gate-more-maybe-bounds.rs:19:20 --> $DIR/feature-gate-more-maybe-bounds.rs:17:20
| |
LL | fn baz<T: ?Trait + ?Trait>(_ : T) {} LL | fn baz<T: ?Trait + ?Trait>(_ : T) {}
| ^^^^^^ | ^^^^^^
error: aborting due to 9 previous errors error: aborting due to 9 previous errors
Some errors have detailed explanations: E0203, E0658. For more information about this error, try `rustc --explain E0203`.
For more information about an error, try `rustc --explain E0203`.

6
tests/ui/parser/trait-object-trait-parens.rs
View File

@@ -6,17 +6,17 @@ fn f<T: (Copy) + (?Sized) + (for<'a> Trait<'a>)>() {}
fn main() { fn main() {
let _: Box<(Obj) + (?Sized) + (for<'a> Trait<'a>)>; let _: Box<(Obj) + (?Sized) + (for<'a> Trait<'a>)>;
//~^ ERROR `?Trait` is not permitted in trait object types //~^ ERROR relaxed bounds are not permitted in trait object types
//~| ERROR only auto traits can be used as additional traits //~| ERROR only auto traits can be used as additional traits
//~| 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
let _: Box<?Sized + (for<'a> Trait<'a>) + (Obj)>; let _: Box<?Sized + (for<'a> Trait<'a>) + (Obj)>;
//~^ ERROR `?Trait` is not permitted in trait object types //~^ ERROR relaxed bounds are not permitted in trait object types
//~| ERROR only auto traits can be used as additional traits //~| ERROR only auto traits can be used as additional traits
//~| 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
let _: Box<for<'a> Trait<'a> + (Obj) + (?Sized)>; let _: Box<for<'a> Trait<'a> + (Obj) + (?Sized)>;
//~^ ERROR `?Trait` is not permitted in trait object types //~^ ERROR relaxed bounds are not permitted in trait object types
//~| ERROR only auto traits can be used as additional traits //~| ERROR only auto traits can be used as additional traits
//~| 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

18
tests/ui/parser/trait-object-trait-parens.stderr
View File

@@ -1,29 +1,20 @@
error[E0658]: `?Trait` is not permitted in trait object types error: relaxed bounds are not permitted in trait object types
--> $DIR/trait-object-trait-parens.rs:8:24 --> $DIR/trait-object-trait-parens.rs:8:24
| |
LL | let _: Box<(Obj) + (?Sized) + (for<'a> Trait<'a>)>; LL | let _: Box<(Obj) + (?Sized) + (for<'a> Trait<'a>)>;
| ^^^^^^^^ | ^^^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in trait object types error: relaxed bounds are not permitted in trait object types
--> $DIR/trait-object-trait-parens.rs:13:16 --> $DIR/trait-object-trait-parens.rs:13:16
| |
LL | let _: Box<?Sized + (for<'a> Trait<'a>) + (Obj)>; LL | let _: Box<?Sized + (for<'a> Trait<'a>) + (Obj)>;
| ^^^^^^ | ^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in trait object types error: relaxed bounds are not permitted in trait object types
--> $DIR/trait-object-trait-parens.rs:18:44 --> $DIR/trait-object-trait-parens.rs:18:44
| |
LL | let _: Box<for<'a> Trait<'a> + (Obj) + (?Sized)>; LL | let _: Box<for<'a> Trait<'a> + (Obj) + (?Sized)>;
| ^^^^^^^^ | ^^^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
warning: trait objects without an explicit `dyn` are deprecated warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/trait-object-trait-parens.rs:8:16 --> $DIR/trait-object-trait-parens.rs:8:16
@@ -100,5 +91,4 @@ LL | let _: Box<for<'a> Trait<'a> + (Obj) + (?Sized)>;
error: aborting due to 6 previous errors; 3 warnings emitted error: aborting due to 6 previous errors; 3 warnings emitted
Some errors have detailed explanations: E0225, E0658. For more information about this error, try `rustc --explain E0225`.
For more information about an error, try `rustc --explain E0225`.

6
tests/ui/sized-hierarchy/default-supertrait.rs
View File

@@ -6,18 +6,18 @@ use std::marker::{MetaSized, PointeeSized};
trait Sized_: Sized { } trait Sized_: Sized { }
trait NegSized: ?Sized { } trait NegSized: ?Sized { }
//~^ ERROR `?Trait` is not permitted in supertraits //~^ ERROR relaxed bounds are not permitted in supertrait bounds
trait MetaSized_: MetaSized { } trait MetaSized_: MetaSized { }
trait NegMetaSized: ?MetaSized { } trait NegMetaSized: ?MetaSized { }
//~^ ERROR `?Trait` is not permitted in supertraits //~^ ERROR relaxed bounds are not permitted in supertrait bounds
trait PointeeSized_: PointeeSized { } trait PointeeSized_: PointeeSized { }
trait NegPointeeSized: ?PointeeSized { } trait NegPointeeSized: ?PointeeSized { }
//~^ ERROR `?Trait` is not permitted in supertraits //~^ ERROR relaxed bounds are not permitted in supertrait bounds
trait Bare {} trait Bare {}

17
tests/ui/sized-hierarchy/default-supertrait.stderr
View File

@@ -1,30 +1,22 @@
error[E0658]: `?Trait` is not permitted in supertraits error: relaxed bounds are not permitted in supertrait bounds
--> $DIR/default-supertrait.rs:8:17 --> $DIR/default-supertrait.rs:8:17
| |
LL | trait NegSized: ?Sized { } LL | trait NegSized: ?Sized { }
| ^^^^^^ | ^^^^^^
| |
= help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
= note: traits are `?Sized` by default = note: traits are `?Sized` by default
error[E0658]: `?Trait` is not permitted in supertraits error: relaxed bounds are not permitted in supertrait bounds
--> $DIR/default-supertrait.rs:13:21 --> $DIR/default-supertrait.rs:13:21
| |
LL | trait NegMetaSized: ?MetaSized { } LL | trait NegMetaSized: ?MetaSized { }
| ^^^^^^^^^^ | ^^^^^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in supertraits error: relaxed bounds are not permitted in supertrait bounds
--> $DIR/default-supertrait.rs:19:24 --> $DIR/default-supertrait.rs:19:24
| |
LL | trait NegPointeeSized: ?PointeeSized { } LL | trait NegPointeeSized: ?PointeeSized { }
| ^^^^^^^^^^^^^ | ^^^^^^^^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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[E0277]: the size for values of type `T` cannot be known error[E0277]: the size for values of type `T` cannot be known
--> $DIR/default-supertrait.rs:52:38 --> $DIR/default-supertrait.rs:52:38
@@ -119,5 +111,4 @@ LL | fn with_bare_trait<T: PointeeSized + Bare + std::marker::MetaSized>() {
error: aborting due to 9 previous errors error: aborting due to 9 previous errors
Some errors have detailed explanations: E0277, E0658. For more information about this error, try `rustc --explain E0277`.
For more information about an error, try `rustc --explain E0277`.

18
tests/ui/traits/maybe-trait-bounds-forbidden-locations.rs
View File

@@ -1,18 +0,0 @@
//! Test that ?Trait bounds are forbidden in supertraits and trait object types.
//!
//! While `?Sized` and other maybe bounds are allowed in type parameter bounds and where clauses,
//! they are explicitly forbidden in certain syntactic positions:
//! - As supertraits in trait definitions
//! - In trait object type expressions
//!
//! See https://github.com/rust-lang/rust/issues/20503
trait Tr: ?Sized {}
//~^ ERROR `?Trait` is not permitted in supertraits
type A1 = dyn Tr + (?Sized);
//~^ ERROR `?Trait` is not permitted in trait object types
type A2 = dyn for<'a> Tr + (?Sized);
//~^ ERROR `?Trait` is not permitted in trait object types
fn main() {}

31
tests/ui/traits/maybe-trait-bounds-forbidden-locations.stderr
View File

@@ -1,31 +0,0 @@
error[E0658]: `?Trait` is not permitted in supertraits
--> $DIR/maybe-trait-bounds-forbidden-locations.rs:10:11
|
LL | trait Tr: ?Sized {}
| ^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
= note: traits are `?Sized` by default
error[E0658]: `?Trait` is not permitted in trait object types
--> $DIR/maybe-trait-bounds-forbidden-locations.rs:13:20
|
LL | type A1 = dyn Tr + (?Sized);
| ^^^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in trait object types
--> $DIR/maybe-trait-bounds-forbidden-locations.rs:15:28
|
LL | type A2 = dyn for<'a> Tr + (?Sized);
| ^^^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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 3 previous errors
For more information about this error, try `rustc --explain E0658`.

18
tests/ui/traits/wf-object/maybe-bound.rs
View File

@@ -1,18 +0,0 @@
// Test that `dyn ... + ?Sized + ...` is okay (though `?Sized` has no effect in trait objects).
trait Foo {}
type _0 = dyn ?Sized + Foo;
//~^ ERROR `?Trait` is not permitted in trait object types
type _1 = dyn Foo + ?Sized;
//~^ ERROR `?Trait` is not permitted in trait object types
type _2 = dyn Foo + ?Sized + ?Sized;
//~^ ERROR `?Trait` is not permitted in trait object types
//~| ERROR `?Trait` is not permitted in trait object types
type _3 = dyn ?Sized + Foo;
//~^ ERROR `?Trait` is not permitted in trait object types
fn main() {}

48
tests/ui/traits/wf-object/maybe-bound.stderr
View File

@@ -1,48 +0,0 @@
error[E0658]: `?Trait` is not permitted in trait object types
--> $DIR/maybe-bound.rs:5:15
|
LL | type _0 = dyn ?Sized + Foo;
| ^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in trait object types
--> $DIR/maybe-bound.rs:8:21
|
LL | type _1 = dyn Foo + ?Sized;
| ^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in trait object types
--> $DIR/maybe-bound.rs:11:21
|
LL | type _2 = dyn Foo + ?Sized + ?Sized;
| ^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in trait object types
--> $DIR/maybe-bound.rs:11:30
|
LL | type _2 = dyn Foo + ?Sized + ?Sized;
| ^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in trait object types
--> $DIR/maybe-bound.rs:15:15
|
LL | type _3 = dyn ?Sized + Foo;
| ^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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 5 previous errors
For more information about this error, try `rustc --explain E0658`.

2
tests/ui/traits/wf-object/only-maybe-bound.rs
View File

@@ -2,6 +2,6 @@
type _0 = dyn ?Sized; type _0 = dyn ?Sized;
//~^ ERROR at least one trait is required for an object type [E0224] //~^ ERROR at least one trait is required for an object type [E0224]
//~| ERROR ?Trait` is not permitted in trait object types //~| ERROR relaxed bounds are not permitted in trait object types
fn main() {} fn main() {}

8
tests/ui/traits/wf-object/only-maybe-bound.stderr
View File

@@ -1,11 +1,8 @@
error[E0658]: `?Trait` is not permitted in trait object types error: relaxed bounds are not permitted in trait object types
--> $DIR/only-maybe-bound.rs:3:15 --> $DIR/only-maybe-bound.rs:3:15
| |
LL | type _0 = dyn ?Sized; LL | type _0 = dyn ?Sized;
| ^^^^^^ | ^^^^^^
|
= help: add `#![feature(more_maybe_bounds)]` 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[E0224]: at least one trait is required for an object type error[E0224]: at least one trait is required for an object type
--> $DIR/only-maybe-bound.rs:3:11 --> $DIR/only-maybe-bound.rs:3:11
@@ -15,5 +12,4 @@ LL | type _0 = dyn ?Sized;
error: aborting due to 2 previous errors error: aborting due to 2 previous errors
Some errors have detailed explanations: E0224, E0658. For more information about this error, try `rustc --explain E0224`.
For more information about an error, try `rustc --explain E0224`.

35
tests/ui/unsized/relaxed-bounds-invalid-places.rs
View File

@@ -1,19 +1,18 @@
// Test that relaxed bounds can only be placed on type parameters defined by the closest item // Test various places where relaxed bounds are not permitted.
// (ignoring relaxed bounds inside `impl Trait` and in associated type defs here). //
// Relaxed bounds are only permitted inside impl-Trait, assoc ty item bounds and
// on type params defined by the closest item.
struct S1<T>(T) where (T): ?Sized; struct S1<T>(T) where (T): ?Sized; //~ ERROR this relaxed bound is not permitted here
//~^ ERROR `?Trait` bounds are only permitted at the point where a type parameter is declared
struct S2<T>(T) where u8: ?Sized; struct S2<T>(T) where u8: ?Sized; //~ ERROR this relaxed bound is not permitted here
//~^ ERROR `?Trait` bounds are only permitted at the point where a type parameter is declared
struct S3<T>(T) where &'static T: ?Sized; struct S3<T>(T) where &'static T: ?Sized; //~ ERROR this relaxed bound is not permitted here
//~^ ERROR `?Trait` bounds are only permitted at the point where a type parameter is declared
trait Trait<'a> {} trait Trait<'a> {}
struct S4<T>(T) where for<'a> T: ?Trait<'a>; struct S4<T>(T) where for<'a> T: ?Trait<'a>;
//~^ ERROR `?Trait` bounds are only permitted at the point where a type parameter is declared //~^ ERROR this relaxed bound is not permitted here
//~| ERROR relaxing a default bound only does something for `?Sized` //~| ERROR relaxing a default bound only does something for `?Sized`
struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized; struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized;
@@ -21,11 +20,17 @@ struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized;
//~| ERROR relaxing a default bound only does something for `?Sized` //~| ERROR relaxing a default bound only does something for `?Sized`
impl<T> S1<T> { impl<T> S1<T> {
fn f() where T: ?Sized {} fn f() where T: ?Sized {} //~ ERROR this relaxed bound is not permitted here
//~^ ERROR `?Trait` bounds are only permitted at the point where a type parameter is declared
} }
fn main() { trait Tr: ?Sized {} //~ ERROR relaxed bounds are not permitted in supertrait bounds
let u = vec![1, 2, 3];
let _s: S5<[u8]> = S5(&u[..]); // OK // Test that relaxed `Sized` bounds are rejected in trait object types:
}
type O1 = dyn Tr + ?Sized; //~ ERROR relaxed bounds are not permitted in trait object types
type O2 = dyn ?Sized + ?Sized + Tr;
//~^ ERROR relaxed bounds are not permitted in trait object types
//~| ERROR relaxed bounds are not permitted in trait object types
fn main() {}

70
tests/ui/unsized/relaxed-bounds-invalid-places.stderr
View File

@@ -1,56 +1,77 @@
error[E0658]: `?Trait` bounds are only permitted at the point where a type parameter is declared error: this relaxed bound is not permitted here
--> $DIR/relaxed-bounds-invalid-places.rs:4:28 --> $DIR/relaxed-bounds-invalid-places.rs:6:28
| |
LL | struct S1<T>(T) where (T): ?Sized; LL | struct S1<T>(T) where (T): ?Sized;
| ^^^^^^ | ^^^^^^
| |
= help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable = note: in this context, relaxed bounds are only allowed on type parameters defined by the closest item
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error[E0658]: `?Trait` bounds are only permitted at the point where a type parameter is declared error: this relaxed bound is not permitted here
--> $DIR/relaxed-bounds-invalid-places.rs:7:27 --> $DIR/relaxed-bounds-invalid-places.rs:8:27
| |
LL | struct S2<T>(T) where u8: ?Sized; LL | struct S2<T>(T) where u8: ?Sized;
| ^^^^^^ | ^^^^^^
| |
= help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable = note: in this context, relaxed bounds are only allowed on type parameters defined by the closest item
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error[E0658]: `?Trait` bounds are only permitted at the point where a type parameter is declared error: this relaxed bound is not permitted here
--> $DIR/relaxed-bounds-invalid-places.rs:10:35 --> $DIR/relaxed-bounds-invalid-places.rs:10:35
| |
LL | struct S3<T>(T) where &'static T: ?Sized; LL | struct S3<T>(T) where &'static T: ?Sized;
| ^^^^^^ | ^^^^^^
| |
= help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable = note: in this context, relaxed bounds are only allowed on type parameters defined by the closest item
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error[E0658]: `?Trait` bounds are only permitted at the point where a type parameter is declared error: this relaxed bound is not permitted here
--> $DIR/relaxed-bounds-invalid-places.rs:15:34 --> $DIR/relaxed-bounds-invalid-places.rs:14:34
| |
LL | struct S4<T>(T) where for<'a> T: ?Trait<'a>; LL | struct S4<T>(T) where for<'a> T: ?Trait<'a>;
| ^^^^^^^^^^ | ^^^^^^^^^^
| |
= help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable = note: in this context, relaxed bounds are only allowed on type parameters defined by the closest item
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error[E0658]: `?Trait` bounds are only permitted at the point where a type parameter is declared error: this relaxed bound is not permitted here
--> $DIR/relaxed-bounds-invalid-places.rs:24:21 --> $DIR/relaxed-bounds-invalid-places.rs:23:21
| |
LL | fn f() where T: ?Sized {} LL | fn f() where T: ?Sized {}
| ^^^^^^ | ^^^^^^
| |
= help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable = note: in this context, relaxed bounds are only allowed on type parameters defined by the closest item
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error: relaxed bounds are not permitted in supertrait bounds
--> $DIR/relaxed-bounds-invalid-places.rs:26:11
|
LL | trait Tr: ?Sized {}
| ^^^^^^
|
= note: traits are `?Sized` by default
error: relaxed bounds are not permitted in trait object types
--> $DIR/relaxed-bounds-invalid-places.rs:30:20
|
LL | type O1 = dyn Tr + ?Sized;
| ^^^^^^
error: relaxed bounds are not permitted in trait object types
--> $DIR/relaxed-bounds-invalid-places.rs:31:15
|
LL | type O2 = dyn ?Sized + ?Sized + Tr;
| ^^^^^^
error: relaxed bounds are not permitted in trait object types
--> $DIR/relaxed-bounds-invalid-places.rs:31:24
|
LL | type O2 = dyn ?Sized + ?Sized + Tr;
| ^^^^^^
error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
--> $DIR/relaxed-bounds-invalid-places.rs:15:34 --> $DIR/relaxed-bounds-invalid-places.rs:14:34
| |
LL | struct S4<T>(T) where for<'a> T: ?Trait<'a>; LL | struct S4<T>(T) where for<'a> T: ?Trait<'a>;
| ^^^^^^^^^^ | ^^^^^^^^^^
error[E0203]: type parameter has more than one relaxed default bound, only one is supported error[E0203]: type parameter has more than one relaxed default bound, only one is supported
--> $DIR/relaxed-bounds-invalid-places.rs:19:33 --> $DIR/relaxed-bounds-invalid-places.rs:18:33
| |
LL | struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized; LL | struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized;
| ^^^^^^^^^^^^^^^ ^^^^^^ | ^^^^^^^^^^^^^^^ ^^^^^^
@@ -59,12 +80,11 @@ LL | struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized;
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
--> $DIR/relaxed-bounds-invalid-places.rs:19:33 --> $DIR/relaxed-bounds-invalid-places.rs:18:33
| |
LL | struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized; LL | struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized;
| ^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^
error: aborting due to 8 previous errors error: aborting due to 12 previous errors
Some errors have detailed explanations: E0203, E0658. For more information about this error, try `rustc --explain E0203`.
For more information about an error, try `rustc --explain E0203`.