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Rollup merge of #121720 - tmandry:split-refining, r=compiler-errors

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Split refining_impl_trait lint into _reachable, _internal variants

As discussed in https://github.com/rust-lang/rust/issues/119535#issuecomment-1909352040:

> We discussed this today in triage and developed a consensus to:
>
> * Add a separate lint against impls that refine a return type defined with RPITIT even when the trait is not crate public.
> * Place that in a lint group along with the analogous crate public lint.
> * Create an issue to solicit feedback on these lints (or perhaps two separate ones).
> * Have the warnings displayed with each lint reference this issue in a similar manner to how we do that today with the required `Self: '0'` bound on GATs.
> * Make a note to review this feedback on 2-3 release cycles.

This points users to https://github.com/rust-lang/rust/issues/121718 to leave feedback.
This commit is contained in:
León Orell Valerian Liehr 2024-03-16 23:28:47 +01:00 committed by GitHub
commit 0995508562
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GPG Key ID: B5690EEEBB952194
13 changed files with 239 additions and 33 deletions
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1
compiler/rustc_hir_analysis/messages.ftl
View File

@ -351,6 +351,7 @@ hir_analysis_rpitit_refined = impl trait in impl method signature does not match
.label = return type from trait method defined here
.unmatched_bound_label = this bound is stronger than that defined on the trait
.note = add `#[allow(refining_impl_trait)]` if it is intended for this to be part of the public API of this crate
.feedback_note = we are soliciting feedback, see issue #121718 <https://github.com/rust-lang/rust/issues/121718> for more information
hir_analysis_self_in_impl_self =
`Self` is not valid in the self type of an impl block

33
compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
View File

@ -2,7 +2,7 @@ use rustc_data_structures::fx::FxIndexSet;
use rustc_hir as hir;
use rustc_hir::def_id::DefId;
use rustc_infer::infer::{outlives::env::OutlivesEnvironment, TyCtxtInferExt};
use rustc_lint_defs::builtin::REFINING_IMPL_TRAIT;
use rustc_lint_defs::builtin::{REFINING_IMPL_TRAIT_INTERNAL, REFINING_IMPL_TRAIT_REACHABLE};
use rustc_middle::traits::{ObligationCause, Reveal};
use rustc_middle::ty::{
self, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperVisitable, TypeVisitable, TypeVisitor,
@ -23,26 +23,23 @@ pub(super) fn check_refining_return_position_impl_trait_in_trait<'tcx>(
if !tcx.impl_method_has_trait_impl_trait_tys(impl_m.def_id) {
return;
}
// unreachable traits don't have any library guarantees, there's no need to do this check.
if trait_m
let is_internal = trait_m
.container_id(tcx)
.as_local()
.is_some_and(|trait_def_id| !tcx.effective_visibilities(()).is_reachable(trait_def_id))
{
return;
}
// If a type in the trait ref is private, then there's also no reason to do this check.
|| impl_trait_ref.args.iter().any(|arg| {
if let Some(ty) = arg.as_type()
&& let Some(self_visibility) = type_visibility(tcx, ty)
{
return !self_visibility.is_public();
}
false
});
// If a type in the trait ref is private, then there's also no reason to do this check.
let impl_def_id = impl_m.container_id(tcx);
for arg in impl_trait_ref.args {
if let Some(ty) = arg.as_type()
&& let Some(self_visibility) = type_visibility(tcx, ty)
&& !self_visibility.is_public()
{
return;
}
}
let impl_m_args = ty::GenericArgs::identity_for_item(tcx, impl_m.def_id);
let trait_m_to_impl_m_args = impl_m_args.rebase_onto(tcx, impl_def_id, impl_trait_ref.args);
let bound_trait_m_sig = tcx.fn_sig(trait_m.def_id).instantiate(tcx, trait_m_to_impl_m_args);
@ -85,6 +82,7 @@ pub(super) fn check_refining_return_position_impl_trait_in_trait<'tcx>(
trait_m.def_id,
impl_m.def_id,
None,
is_internal,
);
return;
};
@ -104,6 +102,7 @@ pub(super) fn check_refining_return_position_impl_trait_in_trait<'tcx>(
trait_m.def_id,
impl_m.def_id,
None,
is_internal,
);
return;
}
@ -198,6 +197,7 @@ pub(super) fn check_refining_return_position_impl_trait_in_trait<'tcx>(
trait_m.def_id,
impl_m.def_id,
Some(span),
is_internal,
);
return;
}
@ -235,6 +235,7 @@ fn report_mismatched_rpitit_signature<'tcx>(
trait_m_def_id: DefId,
impl_m_def_id: DefId,
unmatched_bound: Option<Span>,
is_internal: bool,
) {
let mapping = std::iter::zip(
tcx.fn_sig(trait_m_def_id).skip_binder().bound_vars(),
@ -287,7 +288,7 @@ fn report_mismatched_rpitit_signature<'tcx>(
let span = unmatched_bound.unwrap_or(span);
tcx.emit_node_span_lint(
REFINING_IMPL_TRAIT,
if is_internal { REFINING_IMPL_TRAIT_INTERNAL } else { REFINING_IMPL_TRAIT_REACHABLE },
tcx.local_def_id_to_hir_id(impl_m_def_id.expect_local()),
span,
crate::errors::ReturnPositionImplTraitInTraitRefined {

1
compiler/rustc_hir_analysis/src/errors.rs
View File

@ -1072,6 +1072,7 @@ pub struct UnusedAssociatedTypeBounds {
#[derive(LintDiagnostic)]
#[diag(hir_analysis_rpitit_refined)]
#[note]
#[note(hir_analysis_feedback_note)]
pub(crate) struct ReturnPositionImplTraitInTraitRefined<'tcx> {
#[suggestion(applicability = "maybe-incorrect", code = "{pre}{return_ty}{post}")]
pub impl_return_span: Span,

6
compiler/rustc_lint/src/lib.rs
View File

@ -313,6 +313,12 @@ fn register_builtins(store: &mut LintStore) {
// MACRO_USE_EXTERN_CRATE
);
add_lint_group!(
"refining_impl_trait",
REFINING_IMPL_TRAIT_REACHABLE,
REFINING_IMPL_TRAIT_INTERNAL
);
// Register renamed and removed lints.
store.register_renamed("single_use_lifetime", "single_use_lifetimes");
store.register_renamed("elided_lifetime_in_path", "elided_lifetimes_in_paths");

90
compiler/rustc_lint_defs/src/builtin.rs
View File

@ -79,7 +79,8 @@ declare_lint_pass! {
PROC_MACRO_BACK_COMPAT,
PROC_MACRO_DERIVE_RESOLUTION_FALLBACK,
PUB_USE_OF_PRIVATE_EXTERN_CRATE,
REFINING_IMPL_TRAIT,
REFINING_IMPL_TRAIT_INTERNAL,
REFINING_IMPL_TRAIT_REACHABLE,
RENAMED_AND_REMOVED_LINTS,
REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS,
RUST_2021_INCOMPATIBLE_CLOSURE_CAPTURES,
@ -4402,8 +4403,10 @@ declare_lint! {
}
declare_lint! {
/// The `refining_impl_trait` lint detects usages of return-position impl
/// traits in trait signatures which are refined by implementations.
/// The `refining_impl_trait_reachable` lint detects `impl Trait` return
/// types in method signatures that are refined by a publically reachable
/// trait implementation, meaning the implementation adds information about
/// the return type that is not present in the trait.
///
/// ### Example
///
@ -4425,7 +4428,7 @@ declare_lint! {
/// fn main() {
/// // users can observe that the return type of
/// // `<&str as AsDisplay>::as_display()` is `&str`.
/// let x: &str = "".as_display();
/// let _x: &str = "".as_display();
/// }
/// ```
///
@ -4433,13 +4436,80 @@ declare_lint! {
///
/// ### Explanation
///
/// Return-position impl trait in traits (RPITITs) desugar to associated types,
/// and callers of methods for types where the implementation is known are
/// Callers of methods for types where the implementation is known are
/// able to observe the types written in the impl signature. This may be
/// intended behavior, but may also pose a semver hazard for authors of libraries
/// who do not wish to make stronger guarantees about the types than what is
/// written in the trait signature.
pub REFINING_IMPL_TRAIT,
/// intended behavior, but may also lead to implementation details being
/// revealed unintentionally. In particular, it may pose a semver hazard
/// for authors of libraries who do not wish to make stronger guarantees
/// about the types than what is written in the trait signature.
///
/// `refining_impl_trait` is a lint group composed of two lints:
///
/// * `refining_impl_trait_reachable`, for refinements that are publically
/// reachable outside a crate, and
/// * `refining_impl_trait_internal`, for refinements that are only visible
/// within a crate.
///
/// We are seeking feedback on each of these lints; see issue
/// [#121718](https://github.com/rust-lang/rust/issues/121718) for more
/// information.
pub REFINING_IMPL_TRAIT_REACHABLE,
Warn,
"impl trait in impl method signature does not match trait method signature",
}
declare_lint! {
/// The `refining_impl_trait_internal` lint detects `impl Trait` return
/// types in method signatures that are refined by a trait implementation,
/// meaning the implementation adds information about the return type that
/// is not present in the trait.
///
/// ### Example
///
/// ```rust,compile_fail
/// #![deny(refining_impl_trait)]
///
/// use std::fmt::Display;
///
/// trait AsDisplay {
/// fn as_display(&self) -> impl Display;
/// }
///
/// impl<'s> AsDisplay for &'s str {
/// fn as_display(&self) -> Self {
/// *self
/// }
/// }
///
/// fn main() {
/// // users can observe that the return type of
/// // `<&str as AsDisplay>::as_display()` is `&str`.
/// let _x: &str = "".as_display();
/// }
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// Callers of methods for types where the implementation is known are
/// able to observe the types written in the impl signature. This may be
/// intended behavior, but may also lead to implementation details being
/// revealed unintentionally. In particular, it may pose a semver hazard
/// for authors of libraries who do not wish to make stronger guarantees
/// about the types than what is written in the trait signature.
///
/// `refining_impl_trait` is a lint group composed of two lints:
///
/// * `refining_impl_trait_reachable`, for refinements that are publically
/// reachable outside a crate, and
/// * `refining_impl_trait_internal`, for refinements that are only visible
/// within a crate.
///
/// We are seeking feedback on each of these lints; see issue
/// [#121718](https://github.com/rust-lang/rust/issues/121718) for more
/// information.
pub REFINING_IMPL_TRAIT_INTERNAL,
Warn,
"impl trait in impl method signature does not match trait method signature",
}

4
src/tools/lint-docs/src/groups.rs
View File

@ -16,6 +16,10 @@ static GROUP_DESCRIPTIONS: &[(&str, &str)] = &[
("rust-2018-compatibility", "Lints used to transition code from the 2015 edition to 2018"),
("rust-2021-compatibility", "Lints used to transition code from the 2018 edition to 2021"),
("rust-2024-compatibility", "Lints used to transition code from the 2021 edition to 2024"),
(
"refining-impl-trait",
"Detects refinement of `impl Trait` return types by trait implementations",
),
];
type LintGroups = BTreeMap<String, BTreeSet<String>>;

2
tests/ui/async-await/in-trait/async-example-desugared-boxed.stderr
View File

@ -8,11 +8,13 @@ LL | fn foo(&self) -> Pin<Box<dyn Future<Output = i32> + '_>> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: add `#[allow(refining_impl_trait)]` if it is intended for this to be part of the public API of this crate
= note: we are soliciting feedback, see issue #121718 <https://github.com/rust-lang/rust/issues/121718> for more information
note: the lint level is defined here
--> $DIR/async-example-desugared-boxed.rs:13:12
|
LL | #[warn(refining_impl_trait)]
| ^^^^^^^^^^^^^^^^^^^
= note: `#[warn(refining_impl_trait_reachable)]` implied by `#[warn(refining_impl_trait)]`
help: replace the return type so that it matches the trait
|
LL | fn foo(&self) -> impl Future<Output = i32> {

2
tests/ui/async-await/in-trait/async-example-desugared-manual.stderr
View File

@ -8,11 +8,13 @@ LL | fn foo(&self) -> MyFuture {
| ^^^^^^^^
|
= note: add `#[allow(refining_impl_trait)]` if it is intended for this to be part of the public API of this crate
= note: we are soliciting feedback, see issue #121718 <https://github.com/rust-lang/rust/issues/121718> for more information
note: the lint level is defined here
--> $DIR/async-example-desugared-manual.rs:21:12
|
LL | #[warn(refining_impl_trait)]
| ^^^^^^^^^^^^^^^^^^^
= note: `#[warn(refining_impl_trait_reachable)]` implied by `#[warn(refining_impl_trait)]`
help: replace the return type so that it matches the trait
|
LL | fn foo(&self) -> impl Future<Output = i32> {

3
tests/ui/impl-trait/in-trait/bad-item-bound-within-rpitit.stderr
View File

@ -22,7 +22,8 @@ LL | fn iter(&self) -> impl 'a + Iterator<Item = I::Item<'a>> {
| ^^ this bound is stronger than that defined on the trait
|
= note: add `#[allow(refining_impl_trait)]` if it is intended for this to be part of the public API of this crate
= note: `#[warn(refining_impl_trait)]` on by default
= note: we are soliciting feedback, see issue #121718 <https://github.com/rust-lang/rust/issues/121718> for more information
= note: `#[warn(refining_impl_trait_reachable)]` on by default
help: replace the return type so that it matches the trait
|
LL | fn iter(&self) -> impl Iterator<Item = <Self as Iterable>::Item<'_>> + '_ {

30
tests/ui/impl-trait/in-trait/foreign.rs
View File

@ -17,9 +17,29 @@ impl Foo for Local {
}
}
struct LocalIgnoreRefining;
impl Foo for LocalIgnoreRefining {
#[deny(refining_impl_trait)]
struct LocalOnlyRefiningA;
impl Foo for LocalOnlyRefiningA {
#[warn(refining_impl_trait)]
fn bar(self) -> Arc<String> {
//~^ WARN impl method signature does not match trait method signature
Arc::new(String::new())
}
}
struct LocalOnlyRefiningB;
impl Foo for LocalOnlyRefiningB {
#[warn(refining_impl_trait)]
#[allow(refining_impl_trait_reachable)]
fn bar(self) -> Arc<String> {
//~^ WARN impl method signature does not match trait method signature
Arc::new(String::new())
}
}
struct LocalOnlyRefiningC;
impl Foo for LocalOnlyRefiningC {
#[warn(refining_impl_trait)]
#[allow(refining_impl_trait_internal)]
fn bar(self) -> Arc<String> {
Arc::new(String::new())
}
@ -34,5 +54,7 @@ fn main() {
let &() = Foreign.bar();
let x: Arc<String> = Local.bar();
let x: Arc<String> = LocalIgnoreRefining.bar();
let x: Arc<String> = LocalOnlyRefiningA.bar();
let x: Arc<String> = LocalOnlyRefiningB.bar();
let x: Arc<String> = LocalOnlyRefiningC.bar();
}

39
tests/ui/impl-trait/in-trait/foreign.stderr Normal file
View File

@ -0,0 +1,39 @@
warning: impl trait in impl method signature does not match trait method signature
--> $DIR/foreign.rs:23:21
|
LL | fn bar(self) -> Arc<String> {
| ^^^^^^^^^^^
|
= note: add `#[allow(refining_impl_trait)]` if it is intended for this to be part of the public API of this crate
= note: we are soliciting feedback, see issue #121718 <https://github.com/rust-lang/rust/issues/121718> for more information
note: the lint level is defined here
--> $DIR/foreign.rs:22:12
|
LL | #[warn(refining_impl_trait)]
| ^^^^^^^^^^^^^^^^^^^
= note: `#[warn(refining_impl_trait_internal)]` implied by `#[warn(refining_impl_trait)]`
help: replace the return type so that it matches the trait
|
LL | fn bar(self) -> impl Deref<Target = impl Sized> {
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
warning: impl trait in impl method signature does not match trait method signature
--> $DIR/foreign.rs:33:21
|
LL | fn bar(self) -> Arc<String> {
| ^^^^^^^^^^^
|
= note: add `#[allow(refining_impl_trait)]` if it is intended for this to be part of the public API of this crate
= note: we are soliciting feedback, see issue #121718 <https://github.com/rust-lang/rust/issues/121718> for more information
note: the lint level is defined here
--> $DIR/foreign.rs:31:12
|
LL | #[warn(refining_impl_trait)]
| ^^^^^^^^^^^^^^^^^^^
help: replace the return type so that it matches the trait
|
LL | fn bar(self) -> impl Deref<Target = impl Sized> {
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
warning: 2 warnings emitted

3
tests/ui/impl-trait/in-trait/refine.rs
View File

@ -25,6 +25,7 @@ impl Foo for C {
struct Private;
impl Foo for Private {
fn bar() -> () {}
//~^ ERROR impl method signature does not match trait method signature
}
pub trait Arg<A> {
@ -32,6 +33,7 @@ pub trait Arg<A> {
}
impl Arg<Private> for A {
fn bar() -> () {}
//~^ ERROR impl method signature does not match trait method signature
}
pub trait Late {
@ -52,6 +54,7 @@ mod unreachable {
struct E;
impl UnreachablePub for E {
fn bar() {}
//~^ ERROR impl method signature does not match trait method signature
}
}

58
tests/ui/impl-trait/in-trait/refine.stderr
View File

@ -8,11 +8,13 @@ LL | fn bar() -> impl Copy {}
| ^^^^ this bound is stronger than that defined on the trait
|
= note: add `#[allow(refining_impl_trait)]` if it is intended for this to be part of the public API of this crate
= note: we are soliciting feedback, see issue #121718 <https://github.com/rust-lang/rust/issues/121718> for more information
note: the lint level is defined here
--> $DIR/refine.rs:1:9
|
LL | #![deny(refining_impl_trait)]
| ^^^^^^^^^^^^^^^^^^^
= note: `#[deny(refining_impl_trait_reachable)]` implied by `#[deny(refining_impl_trait)]`
help: replace the return type so that it matches the trait
|
LL | fn bar() -> impl Sized {}
@ -28,6 +30,7 @@ LL | fn bar() {}
| ^^^^^^^^
|
= note: add `#[allow(refining_impl_trait)]` if it is intended for this to be part of the public API of this crate
= note: we are soliciting feedback, see issue #121718 <https://github.com/rust-lang/rust/issues/121718> for more information
help: replace the return type so that it matches the trait
|
LL | fn bar()-> impl Sized {}
@ -43,13 +46,47 @@ LL | fn bar() -> () {}
| ^^
|
= note: add `#[allow(refining_impl_trait)]` if it is intended for this to be part of the public API of this crate
= note: we are soliciting feedback, see issue #121718 <https://github.com/rust-lang/rust/issues/121718> for more information
help: replace the return type so that it matches the trait
|
LL | fn bar() -> impl Sized {}
| ~~~~~~~~~~
error: impl trait in impl method signature does not match trait method signature
--> $DIR/refine.rs:43:27
--> $DIR/refine.rs:27:17
|
LL | fn bar() -> impl Sized;
| ---------- return type from trait method defined here
...
LL | fn bar() -> () {}
| ^^
|
= note: add `#[allow(refining_impl_trait)]` if it is intended for this to be part of the public API of this crate
= note: we are soliciting feedback, see issue #121718 <https://github.com/rust-lang/rust/issues/121718> for more information
= note: `#[deny(refining_impl_trait_internal)]` implied by `#[deny(refining_impl_trait)]`
help: replace the return type so that it matches the trait
|
LL | fn bar() -> impl Sized {}
| ~~~~~~~~~~
error: impl trait in impl method signature does not match trait method signature
--> $DIR/refine.rs:35:17
|
LL | fn bar() -> impl Sized;
| ---------- return type from trait method defined here
...
LL | fn bar() -> () {}
| ^^
|
= note: add `#[allow(refining_impl_trait)]` if it is intended for this to be part of the public API of this crate
= note: we are soliciting feedback, see issue #121718 <https://github.com/rust-lang/rust/issues/121718> for more information
help: replace the return type so that it matches the trait
|
LL | fn bar() -> impl Sized {}
| ~~~~~~~~~~
error: impl trait in impl method signature does not match trait method signature
--> $DIR/refine.rs:45:27
|
LL | fn bar<'a>(&'a self) -> impl Sized + 'a;
| --------------- return type from trait method defined here
@ -58,10 +95,27 @@ LL | fn bar(&self) -> impl Copy + '_ {}
| ^^^^ this bound is stronger than that defined on the trait
|
= note: add `#[allow(refining_impl_trait)]` if it is intended for this to be part of the public API of this crate
= note: we are soliciting feedback, see issue #121718 <https://github.com/rust-lang/rust/issues/121718> for more information
help: replace the return type so that it matches the trait
|
LL | fn bar(&self) -> impl Sized + '_ {}
| ~~~~~~~~~~~~~~~
error: aborting due to 4 previous errors
error: impl trait in impl method signature does not match trait method signature
--> $DIR/refine.rs:56:9
|
LL | fn bar() -> impl Sized;
| ---------- return type from trait method defined here
...
LL | fn bar() {}
| ^^^^^^^^
|
= note: add `#[allow(refining_impl_trait)]` if it is intended for this to be part of the public API of this crate
= note: we are soliciting feedback, see issue #121718 <https://github.com/rust-lang/rust/issues/121718> for more information
help: replace the return type so that it matches the trait
|
LL | fn bar()-> impl Sized {}
| +++++++++++++
error: aborting due to 7 previous errors