Skip to content

Commit

Permalink
Avoid ICE in trait without dyn lint
Browse files Browse the repository at this point in the history
Do not attempt to provide an accurate suggestion for `impl Trait`
in bare trait types when linting. Instead, only do the object
safety check when an E0782 is already going to be emitted in the
2021 edition.

Fix #120241.
estebank committed Jan 29, 2024
1 parent fb4bca0 commit 09f16b5
Showing 16 changed files with 221 additions and 125 deletions.
8 changes: 3 additions & 5 deletions compiler/rustc_hir_analysis/src/astconv/lint.rs
Original file line number Diff line number Diff line change
@@ -132,7 +132,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
],
Applicability::MachineApplicable,
);
} else if diag.is_error() && is_downgradable {
} else if is_downgradable {
// We'll emit the object safety error already, with a structured suggestion.
diag.downgrade_to_delayed_bug();
}
@@ -158,7 +158,7 @@ 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`"));
if diag.is_error() && is_downgradable {
if is_downgradable {
// We'll emit the object safety error already, with a structured suggestion.
diag.downgrade_to_delayed_bug();
}
@@ -241,9 +241,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
} else {
let msg = "trait objects without an explicit `dyn` are deprecated";
tcx.node_span_lint(BARE_TRAIT_OBJECTS, self_ty.hir_id, self_ty.span, msg, |lint| {
if self_ty.span.can_be_used_for_suggestions()
&& !self.maybe_lint_impl_trait(self_ty, lint)
{
if self_ty.span.can_be_used_for_suggestions() {
lint.multipart_suggestion_verbose(
"use `dyn`",
sugg,
12 changes: 12 additions & 0 deletions tests/ui/object-safety/avoid-ice-on-warning-2.new.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
error[E0038]: the trait `Copy` cannot be made into an object
--> $DIR/avoid-ice-on-warning-2.rs:4:13
|
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

For more information about this error, try `rustc --explain E0038`.
Original file line number Diff line number Diff line change
@@ -1,43 +1,33 @@
warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning-2.rs:1:13
--> $DIR/avoid-ice-on-warning-2.rs:4:13
|
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`
help: use `dyn`
|
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 {
| ++++
LL | fn id<F>(f: dyn Copy) -> usize {
| +++

warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning-2.rs:1:13
--> $DIR/avoid-ice-on-warning-2.rs:4:13
|
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
help: use `dyn`
|
LL | fn id<F>(f: impl Copy) -> usize {
| ++++
LL | fn id<F>(f: dyn Copy) -> usize {
| +++

error[E0038]: the trait `Copy` cannot be made into an object
--> $DIR/avoid-ice-on-warning-2.rs:1:13
--> $DIR/avoid-ice-on-warning-2.rs:4:13
|
LL | fn id<F>(f: Copy) -> usize {
| ^^^^ `Copy` cannot be made into an object
13 changes: 8 additions & 5 deletions tests/ui/object-safety/avoid-ice-on-warning-2.rs
Original file line number Diff line number Diff line change
@@ -1,9 +1,12 @@
// revisions: old new
//[old] edition:2015
//[new] edition:2021
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
//~^ ERROR the trait `Copy` cannot be made into an object
//[old]~| WARN trait objects without an explicit `dyn` are deprecated
//[old]~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
//[old]~| WARN trait objects without an explicit `dyn` are deprecated
//[old]~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
f()
}
fn main() {}
47 changes: 47 additions & 0 deletions tests/ui/object-safety/avoid-ice-on-warning-3.new.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,47 @@
error[E0038]: the trait `A` cannot be made into an object
--> $DIR/avoid-ice-on-warning-3.rs:4:19
|
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:12:14
|
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; }
| +++++++++++++++++

error[E0038]: the trait `B` cannot be made into an object
--> $DIR/avoid-ice-on-warning-3.rs:12:19
|
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:4:14
|
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

For more information about this error, try `rustc --explain E0038`.
Original file line number Diff line number Diff line change
@@ -1,93 +1,78 @@
warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning-3.rs:9:19
--> $DIR/avoid-ice-on-warning-3.rs:4:19
|
LL | trait A { fn g(b: B) -> B; }
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: `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
help: use `dyn`
|
LL | trait A { fn g(b: impl B) -> B; }
| ++++
LL | trait B { fn f(a: dyn A) -> A; }
| +++

warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning-3.rs:9:25
--> $DIR/avoid-ice-on-warning-3.rs:4:25
|
LL | trait A { fn g(b: B) -> B; }
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: `B` is not object safe, use `impl B` to return an opaque type, as long as you return a single underlying type
help: use `dyn`
|
LL | trait A { fn g(b: B) -> impl B; }
| ++++
LL | trait B { fn f(a: A) -> dyn A; }
| +++

warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning-3.rs:1:19
--> $DIR/avoid-ice-on-warning-3.rs:12:19
|
LL | trait B { fn f(a: A) -> A; }
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: `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
help: use `dyn`
|
LL | trait B { fn f(a: impl A) -> A; }
| ++++
LL | trait A { fn g(b: dyn B) -> B; }
| +++

warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning-3.rs:1:25
--> $DIR/avoid-ice-on-warning-3.rs:12:25
|
LL | trait B { fn f(a: A) -> A; }
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: `A` is not object safe, use `impl A` to return an opaque type, as long as you return a single underlying type
help: use `dyn`
|
LL | trait B { fn f(a: A) -> impl A; }
| ++++
LL | trait A { fn g(b: B) -> dyn B; }
| +++

warning: trait objects without an explicit `dyn` are deprecated
--> $DIR/avoid-ice-on-warning-3.rs:1:19
--> $DIR/avoid-ice-on-warning-3.rs:4:19
|
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
help: use `dyn`
|
LL | trait B { fn f(a: impl A) -> A; }
| ++++
LL | trait B { fn f(a: dyn A) -> A; }
| +++

error[E0038]: the trait `A` cannot be made into an object
--> $DIR/avoid-ice-on-warning-3.rs:1:19
--> $DIR/avoid-ice-on-warning-3.rs:4:19
|
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
--> $DIR/avoid-ice-on-warning-3.rs:12:14
|
LL | trait A { fn g(b: B) -> B; }
| - ^ ...because associated function `g` has no `self` parameter
@@ -103,32 +88,27 @@ 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
--> $DIR/avoid-ice-on-warning-3.rs:12:19
|
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
help: use `dyn`
|
LL | trait A { fn g(b: impl B) -> B; }
| ++++
LL | trait A { fn g(b: dyn B) -> B; }
| +++

error[E0038]: the trait `B` cannot be made into an object
--> $DIR/avoid-ice-on-warning-3.rs:9:19
--> $DIR/avoid-ice-on-warning-3.rs:12:19
|
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
--> $DIR/avoid-ice-on-warning-3.rs:4:14
|
LL | trait B { fn f(a: A) -> A; }
| - ^ ...because associated function `f` has no `self` parameter
31 changes: 17 additions & 14 deletions tests/ui/object-safety/avoid-ice-on-warning-3.rs
Original file line number Diff line number Diff line change
@@ -1,17 +1,20 @@
// revisions: old new
//[old] edition:2015
//[new] edition:2021
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
//~^ ERROR the trait `A` cannot be made into an object
//[old]~| WARN trait objects without an explicit `dyn` are deprecated
//[old]~| WARN trait objects without an explicit `dyn` are deprecated
//[old]~| WARN trait objects without an explicit `dyn` are deprecated
//[old]~| WARN this is accepted in the current edition
//[old]~| WARN this is accepted in the current edition
//[old]~| WARN this is accepted in the current edition
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
//~^ ERROR the trait `B` cannot be made into an object
//[old]~| WARN trait objects without an explicit `dyn` are deprecated
//[old]~| WARN trait objects without an explicit `dyn` are deprecated
//[old]~| WARN trait objects without an explicit `dyn` are deprecated
//[old]~| WARN this is accepted in the current edition
//[old]~| WARN this is accepted in the current edition
//[old]~| WARN this is accepted in the current edition
fn main() {}
15 changes: 15 additions & 0 deletions tests/ui/object-safety/avoid-ice-on-warning.new.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
error: return types are denoted using `->`
--> $DIR/avoid-ice-on-warning.rs:4:23
|
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:4:36
|
LL | fn call_this<F>(f: F) : Fn(&str) + call_that {}
| ^^^^^^^^^ not found in this scope

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0405`.
Original file line number Diff line number Diff line change
@@ -1,28 +1,28 @@
error: return types are denoted using `->`
--> $DIR/avoid-ice-on-warning.rs:1:23
--> $DIR/avoid-ice-on-warning.rs:4:23
|
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
--> $DIR/avoid-ice-on-warning.rs:4:36
|
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
--> $DIR/avoid-ice-on-warning.rs:4:25
|
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
help: use `dyn`
|
LL | fn call_this<F>(f: F) : impl Fn(&str) + call_that {}
| ++++
LL | fn call_this<F>(f: F) : dyn Fn(&str) + call_that {}
| +++

error: aborting due to 2 previous errors; 1 warning emitted

7 changes: 5 additions & 2 deletions tests/ui/object-safety/avoid-ice-on-warning.rs
Original file line number Diff line number Diff line change
@@ -1,6 +1,9 @@
// revisions: old new
//[old] edition:2015
//[new] edition:2021
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!
//[old]~| WARN trait objects without an explicit `dyn` are deprecated
//[old]~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
fn main() {}
9 changes: 0 additions & 9 deletions tests/ui/object-safety/bare-trait-dont-suggest-dyn.fixed

This file was deleted.

16 changes: 16 additions & 0 deletions tests/ui/object-safety/bare-trait-dont-suggest-dyn.new.fixed
Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
// revisions: old new
//[old] edition:2015
//[new] edition:2021
//[new] run-rustfix
// FIXME: the test suite tries to create a crate called `bare_trait_dont_suggest_dyn.new`
#![crate_name="bare_trait_dont_suggest_dyn"]
#![deny(bare_trait_objects)]
fn ord_prefer_dot(s: String) -> impl Ord {
//~^ ERROR the trait `Ord` cannot be made into an object
//[old]~| ERROR trait objects without an explicit `dyn` are deprecated
//[old]~| WARNING this is accepted in the current edition (Rust 2015)
(s.starts_with("."), s)
}
fn main() {
let _ = ord_prefer_dot(String::new());
}
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
error[E0038]: the trait `Ord` cannot be made into an object
--> $DIR/bare-trait-dont-suggest-dyn.rs:3:33
--> $DIR/bare-trait-dont-suggest-dyn.rs:8:33
|
LL | fn ord_prefer_dot(s: String) -> Ord {
| ^^^ `Ord` cannot be made into an object
39 changes: 39 additions & 0 deletions tests/ui/object-safety/bare-trait-dont-suggest-dyn.old.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,39 @@
error: trait objects without an explicit `dyn` are deprecated
--> $DIR/bare-trait-dont-suggest-dyn.rs:8:33
|
LL | fn ord_prefer_dot(s: String) -> Ord {
| ^^^
|
= 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: the lint level is defined here
--> $DIR/bare-trait-dont-suggest-dyn.rs:7:9
|
LL | #![deny(bare_trait_objects)]
| ^^^^^^^^^^^^^^^^^^
help: use `dyn`
|
LL | fn ord_prefer_dot(s: String) -> dyn Ord {
| +++

error[E0038]: the trait `Ord` cannot be made into an object
--> $DIR/bare-trait-dont-suggest-dyn.rs:8:33
|
LL | fn ord_prefer_dot(s: String) -> Ord {
| ^^^ `Ord` 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>
--> $SRC_DIR/core/src/cmp.rs:LL:COL
|
= note: the trait cannot be made into an object because it uses `Self` as a type parameter
::: $SRC_DIR/core/src/cmp.rs:LL:COL
|
= note: the trait cannot be made into an object because it uses `Self` as a type parameter
help: consider using an opaque type instead
|
LL | fn ord_prefer_dot(s: String) -> impl Ord {
| ++++

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0038`.
9 changes: 8 additions & 1 deletion tests/ui/object-safety/bare-trait-dont-suggest-dyn.rs
Original file line number Diff line number Diff line change
@@ -1,7 +1,14 @@
// run-rustfix
// revisions: old new
//[old] edition:2015
//[new] edition:2021
//[new] run-rustfix
// FIXME: the test suite tries to create a crate called `bare_trait_dont_suggest_dyn.new`
#![crate_name="bare_trait_dont_suggest_dyn"]
#![deny(bare_trait_objects)]
fn ord_prefer_dot(s: String) -> Ord {
//~^ ERROR the trait `Ord` cannot be made into an object
//[old]~| ERROR trait objects without an explicit `dyn` are deprecated
//[old]~| WARNING this is accepted in the current edition (Rust 2015)
(s.starts_with("."), s)
}
fn main() {
14 changes: 3 additions & 11 deletions tests/ui/traits/bound/not-on-bare-trait.stderr
Original file line number Diff line number Diff line change
@@ -7,18 +7,10 @@ LL | fn foo(_x: Foo + Send) {
= 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: use a new generic type parameter, constrained by `Foo + Send`
help: use `dyn`
|
LL | fn foo<T: Foo + Send>(_x: T) {
| +++++++++++++++ ~
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 foo(_x: impl Foo + Send) {
| ++++
help: alternatively, use a trait object to accept any type that implements `Foo + Send`, accessing its methods at runtime using dynamic dispatch
|
LL | fn foo(_x: &(dyn Foo + Send)) {
| +++++ +
LL | fn foo(_x: dyn Foo + Send) {
| +++

error[E0277]: the size for values of type `(dyn Foo + Send + 'static)` cannot be known at compilation time
--> $DIR/not-on-bare-trait.rs:7:8

0 comments on commit 09f16b5

Please sign in to comment.