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Move check to existing pass 

This alters the diagnostics a bit, as the trait method is still stable.
The only thing this check does is ensure that compilation fails if a
trait implementation is declared const-stable.
This commit is contained in:
Jacob Pratt 2022-02-22 14:54:47 -05:00 committed by Oli Scherer
parent f0620c9503
commit 5ff331142e
7 changed files with 61 additions and 157 deletions
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4
compiler/rustc_interface/src/passes.rs
View File

@ -970,10 +970,6 @@ fn analysis(tcx: TyCtxt<'_>, (): ()) -> Result<()> {
sess.time("layout_testing", || layout_test::test_layout(tcx));
sess.time("stable_impl_const_trait_checking", || {
rustc_passes::stability::check_const_impl_trait(tcx)
});
// Avoid overwhelming user with errors if borrow checking failed.
// I'm not sure how helpful this is, to be honest, but it avoids a
// lot of annoying errors in the ui tests (basically,

82
compiler/rustc_passes/src/stability.rs
View File

@ -9,7 +9,6 @@ use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::{LocalDefId, CRATE_DEF_ID};
use rustc_hir::hir_id::CRATE_HIR_ID;
use rustc_hir::intravisit::{self, Visitor};
use rustc_hir::itemlikevisit::ItemLikeVisitor;
use rustc_hir::{FieldDef, Generics, HirId, Item, TraitRef, Ty, TyKind, Variant};
use rustc_middle::hir::nested_filter;
use rustc_middle::middle::privacy::AccessLevels;
@ -606,44 +605,6 @@ impl<'tcx> Visitor<'tcx> for MissingStabilityAnnotations<'tcx> {
// stable (assuming they have not inherited instability from their parent).
}
struct CheckStableConstImplTrait<'tcx> {
tcx: TyCtxt<'tcx>,
}
impl<'tcx> ItemLikeVisitor<'tcx> for CheckStableConstImplTrait<'tcx> {
fn visit_item(&mut self, item: &'tcx Item<'tcx>) {
if !matches!(
item.kind,
hir::ItemKind::Impl(hir::Impl {
of_trait: Some(_),
constness: hir::Constness::Const,
..
})
) {
return;
}
if self.tcx.lookup_const_stability(item.def_id).map_or(false, |stab| stab.is_const_stable())
{
self.tcx
.sess
.struct_span_err(item.span, "trait implementations cannot be const stable yet")
.note("see issue #67792 <https://github.com/rust-lang/rust/issues/67792> for more information")
.emit();
}
}
fn visit_trait_item(&mut self, _trait_item: &'tcx hir::TraitItem<'tcx>) {
// Nothing to do here.
}
fn visit_impl_item(&mut self, _impl_item: &'tcx hir::ImplItem<'tcx>) {
// Nothing to do here.
}
fn visit_foreign_item(&mut self, _foreign_item: &'tcx hir::ForeignItem<'tcx>) {
// Nothing to do here.
}
}
fn stability_index(tcx: TyCtxt<'_>, (): ()) -> Index {
let mut index = Index {
stab_map: Default::default(),
@ -748,16 +709,23 @@ impl<'tcx> Visitor<'tcx> for Checker<'tcx> {
// For implementations of traits, check the stability of each item
// individually as it's possible to have a stable trait with unstable
// items.
hir::ItemKind::Impl(hir::Impl { of_trait: Some(ref t), self_ty, items, .. }) => {
if self.tcx.features().staged_api {
hir::ItemKind::Impl(hir::Impl {
of_trait: Some(ref t),
self_ty,
items,
constness,
..
}) => {
let features = self.tcx.features();
if features.staged_api {
let attrs = self.tcx.hir().attrs(item.hir_id());
let (stab, const_stab) = attr::find_stability(&self.tcx.sess, attrs, item.span);
// If this impl block has an #[unstable] attribute, give an
// error if all involved types and traits are stable, because
// it will have no effect.
// See: https://github.com/rust-lang/rust/issues/55436
let attrs = self.tcx.hir().attrs(item.hir_id());
if let (Some((Stability { level: attr::Unstable { .. }, .. }, span)), _) =
attr::find_stability(&self.tcx.sess, attrs, item.span)
{
if let Some((Stability { level: attr::Unstable { .. }, .. }, span)) = stab {
let mut c = CheckTraitImplStable { tcx: self.tcx, fully_stable: true };
c.visit_ty(self_ty);
c.visit_trait_ref(t);
@ -773,6 +741,19 @@ impl<'tcx> Visitor<'tcx> for Checker<'tcx> {
);
}
}
// `#![feature(const_trait_impl)]` is unstable, so any impl declared stable
// needs to have an error emitted.
if features.const_trait_impl
&& constness == hir::Constness::Const
&& const_stab.map_or(false, |(stab, _)| stab.is_const_stable())
{
self.tcx
.sess
.struct_span_err(item.span, "trait implementations cannot be const stable yet")
.note("see issue #67792 <https://github.com/rust-lang/rust/issues/67792> for more information")
.emit();
}
}
for impl_item_ref in *items {
@ -864,17 +845,6 @@ impl<'tcx> Visitor<'tcx> for CheckTraitImplStable<'tcx> {
}
}
pub fn check_const_impl_trait(tcx: TyCtxt<'_>) {
let features = tcx.features(); // FIXME How cheap is this call?
// Both feature gates have to be enabled for this check to have any effect.
if !features.staged_api || !features.const_trait_impl {
return;
}
let mut visitor = CheckStableConstImplTrait { tcx };
tcx.hir().visit_all_item_likes(&mut visitor);
}
/// Given the list of enabled features that were not language features (i.e., that
/// were expected to be library features), and the list of features used from
/// libraries, identify activated features that don't exist and error about them.

43
src/test/ui/rfc-2632-const-trait-impl/stability.rs
View File

@ -1,43 +0,0 @@
#![feature(const_trait_impl)]
#![feature(staged_api)]
#![stable(feature = "rust1", since = "1.0.0")]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Int(i32);
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_stable(feature = "rust1", since = "1.0.0")]
impl const std::ops::Sub for Int {
//~^ ERROR trait implementations cannot be const stable yet
type Output = Self;
fn sub(self, rhs: Self) -> Self {
Int(self.0 - rhs.0)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_unstable(feature = "const_add", issue = "none")]
impl const std::ops::Add for Int {
type Output = Self;
fn add(self, rhs: Self) -> Self {
Int(self.0 + rhs.0)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_stable(feature = "rust1", since = "1.0.0")]
pub const fn const_err() {
Int(0) + Int(0);
//~^ ERROR not yet stable as a const fn
Int(0) - Int(0);
}
#[stable(feature = "rust1", since = "1.0.0")]
pub fn non_const_success() {
Int(0) + Int(0);
Int(0) - Int(0);
}
fn main() {}

24
src/test/ui/rfc-2632-const-trait-impl/stability.stderr
View File

@ -1,24 +0,0 @@
error: `<Int as Add>::add` is not yet stable as a const fn
--> $DIR/stability.rs:32:5
|
LL | Int(0) + Int(0);
| ^^^^^^^^^^^^^^^
|
= help: const-stable functions can only call other const-stable functions
error: trait implementations cannot be const stable yet
--> $DIR/stability.rs:10:1
|
LL | / impl const std::ops::Sub for Int {
LL | |
LL | | type Output = Self;
LL | |
... |
LL | | }
LL | | }
| |_^
|
= note: see issue #67792 <https://github.com/rust-lang/rust/issues/67792> for more information
error: aborting due to 2 previous errors

24
src/test/ui/rfc-2632-const-trait-impl/staged-api.rs
View File

@ -11,26 +11,36 @@ extern crate staged_api;
use staged_api::*;
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Stable;
pub struct Foo;
#[stable(feature = "rust1", since = "1.0.0")]
#[cfg_attr(stable, rustc_const_stable(feature = "rust1", since = "1.0.0"))]
impl const MyTrait for Stable {
#[cfg_attr(unstable, rustc_const_unstable(feature = "foo", issue = "none"))]
impl const MyTrait for Foo {
//[stable]~^ ERROR trait implementations cannot be const stable yet
//[unstable]~^^ ERROR implementation has missing const stability attribute
fn func() {}
}
// Const stability has no impact on usage in non-const contexts.
fn non_const_context() {
Unstable::func();
Stable::func();
Foo::func();
}
#[unstable(feature = "none", issue = "none")]
const fn const_context() {
Unstable::func();
//[stable]~^ ERROR `<staged_api::Unstable as staged_api::MyTrait>::func` is not yet stable as a const fn
Stable::func();
// ^ This is okay regardless of whether the `unstable` feature is enabled, as this function is
// not const-stable.
Foo::func();
//[unstable]~^ not yet stable as a const fn
}
#[stable(feature = "rust1", since = "1.0.0")]
const fn stable_const_context() {
Unstable::func();
//[unstable]~^ ERROR not yet stable as a const fn
Foo::func();
//[unstable]~^ ERROR not yet stable as a const fn
}
fn main() {}

17
src/test/ui/rfc-2632-const-trait-impl/staged-api.stable.stderr
View File

@ -1,22 +1,11 @@
error: `<staged_api::Unstable as staged_api::MyTrait>::func` is not yet stable as a const fn
--> $DIR/staged-api.rs:31:5
|
LL | Unstable::func();
| ^^^^^^^^^^^^^^^^
|
= help: add `#![feature(unstable)]` to the crate attributes to enable
error: trait implementations cannot be const stable yet
error: implementation has missing const stability attribute
--> $DIR/staged-api.rs:18:1
|
LL | / impl const MyTrait for Stable {
LL | |
LL | / impl const MyTrait for Foo {
LL | |
LL | | fn func() {}
LL | | }
| |_^
|
= note: see issue #67792 <https://github.com/rust-lang/rust/issues/67792> for more information
error: aborting due to 2 previous errors
error: aborting due to previous error

24
src/test/ui/rfc-2632-const-trait-impl/staged-api.unstable.stderr
View File

@ -1,12 +1,18 @@
error: implementation has missing const stability attribute
--> $DIR/staged-api.rs:18:1
error: `<Foo as staged_api::MyTrait>::func` is not yet stable as a const fn
--> $DIR/staged-api.rs:34:5
|
LL | / impl const MyTrait for Stable {
LL | |
LL | |
LL | | fn func() {}
LL | | }
| |_^
LL | Foo::func();
| ^^^^^^^^^^^
|
= help: add `#![feature(foo)]` to the crate attributes to enable
error: aborting due to previous error
error: `<Foo as staged_api::MyTrait>::func` is not yet stable as a const fn
--> $DIR/staged-api.rs:42:5
|
LL | Foo::func();
| ^^^^^^^^^^^
|
= help: add `#![feature(foo)]` to the crate attributes to enable
error: aborting due to 2 previous errors