Skip to content

Commit

Permalink
Add feature gate, not working yet
Browse files Browse the repository at this point in the history
  • Loading branch information
compiler-errors committed Dec 9, 2024
1 parent f6cb952 commit a9fc2e2
Show file tree
Hide file tree
Showing 5 changed files with 113 additions and 11 deletions.
2 changes: 2 additions & 0 deletions compiler/rustc_feature/src/unstable.rs
Original file line number Diff line number Diff line change
Expand Up @@ -390,6 +390,8 @@ declare_features! (
(unstable, associated_type_defaults, "1.2.0", Some(29661)),
/// Allows `async || body` closures.
(unstable, async_closure, "1.37.0", Some(62290)),
/// Allows async functions to be called from `dyn Trait`.
(incomplete, async_fn_in_dyn_trait, "CURRENT_RUSTC_VERSION", Some(133119)),
/// Allows `#[track_caller]` on async functions.
(unstable, async_fn_track_caller, "1.73.0", Some(110011)),
/// Allows `for await` loops.
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_span/src/symbol.rs
Original file line number Diff line number Diff line change
Expand Up @@ -461,6 +461,7 @@ symbols! {
async_drop_slice,
async_drop_surface_drop_in_place,
async_fn,
async_fn_in_dyn_trait,
async_fn_in_trait,
async_fn_kind_helper,
async_fn_kind_upvars,
Expand Down
59 changes: 48 additions & 11 deletions compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@ use rustc_abi::BackendRepr;
use rustc_errors::FatalError;
use rustc_hir as hir;
use rustc_hir::def_id::DefId;
use rustc_middle::bug;
use rustc_middle::query::Providers;
use rustc_middle::ty::{
self, EarlyBinder, ExistentialPredicateStableCmpExt as _, GenericArgs, Ty, TyCtxt,
Expand Down Expand Up @@ -901,23 +902,59 @@ fn contains_illegal_impl_trait_in_trait<'tcx>(
fn_def_id: DefId,
ty: ty::Binder<'tcx, Ty<'tcx>>,
) -> Option<MethodViolationCode> {
// This would be caught below, but rendering the error as a separate
// `async-specific` message is better.
let ty = tcx.liberate_late_bound_regions(fn_def_id, ty);

if tcx.asyncness(fn_def_id).is_async() {
return Some(MethodViolationCode::AsyncFn);
// FIXME(async_fn_in_dyn_trait): Think of a better way to unify these code paths
// to issue an appropriate feature suggestion when users try to use AFIDT.
// Obviously we must only do this once AFIDT is finished enough to actually be usable.
if tcx.features().async_fn_in_dyn_trait() {
let ty::Alias(ty::Projection, proj) = *ty.kind() else {
bug!("expected async fn in trait to return an RPITIT");
};
assert!(tcx.is_impl_trait_in_trait(proj.def_id));

// FIXME(async_fn_in_dyn_trait): We should check that this bound is legal too,
// and stop relying on `async fn` in the definition.
for bound in tcx.item_bounds(proj.def_id).instantiate(tcx, proj.args) {
if let Some(violation) = bound
.visit_with(&mut IllegalRpititVisitor { tcx, allowed: Some(proj) })
.break_value()
{
return Some(violation);
}
}

None
} else {
// Rendering the error as a separate `async-specific` message is better.
Some(MethodViolationCode::AsyncFn)
}
} else {
ty.visit_with(&mut IllegalRpititVisitor { tcx, allowed: None }).break_value()
}
}

struct IllegalRpititVisitor<'tcx> {
tcx: TyCtxt<'tcx>,
allowed: Option<ty::AliasTy<'tcx>>,
}

impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for IllegalRpititVisitor<'tcx> {
type Result = ControlFlow<MethodViolationCode>;

// FIXME(RPITIT): Perhaps we should use a visitor here?
ty.skip_binder().walk().find_map(|arg| {
if let ty::GenericArgKind::Type(ty) = arg.unpack()
&& let ty::Alias(ty::Projection, proj) = ty.kind()
&& tcx.is_impl_trait_in_trait(proj.def_id)
fn visit_ty(&mut self, ty: Ty<'tcx>) -> Self::Result {
if let ty::Alias(ty::Projection, proj) = *ty.kind()
&& Some(proj) != self.allowed
&& self.tcx.is_impl_trait_in_trait(proj.def_id)
{
Some(MethodViolationCode::ReferencesImplTraitInTrait(tcx.def_span(proj.def_id)))
ControlFlow::Break(MethodViolationCode::ReferencesImplTraitInTrait(
self.tcx.def_span(proj.def_id),
))
} else {
None
ty.super_visit_with(self)
}
})
}
}

pub(crate) fn provide(providers: &mut Providers) {
Expand Down
14 changes: 14 additions & 0 deletions tests/ui/feature-gates/feature-gate-async-fn-in-dyn-trait.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
//@ edition: 2021

trait Foo {
async fn bar(&self);
}

async fn takes_dyn_trait(x: &dyn Foo) {
//~^ ERROR the trait `Foo` cannot be made into an object
x.bar().await;
//~^ ERROR the trait `Foo` cannot be made into an object
//~| ERROR the trait `Foo` cannot be made into an object
}

fn main() {}
48 changes: 48 additions & 0 deletions tests/ui/feature-gates/feature-gate-async-fn-in-dyn-trait.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,48 @@
error[E0038]: the trait `Foo` cannot be made into an object
--> $DIR/feature-gate-async-fn-in-dyn-trait.rs:7:30
|
LL | async fn takes_dyn_trait(x: &dyn Foo) {
| ^^^^^^^ `Foo` cannot be made into an object
|
note: for a trait to be "dyn-compatible" 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/feature-gate-async-fn-in-dyn-trait.rs:4:14
|
LL | trait Foo {
| --- this trait cannot be made into an object...
LL | async fn bar(&self);
| ^^^ ...because method `bar` is `async`
= help: consider moving `bar` to another trait

error[E0038]: the trait `Foo` cannot be made into an object
--> $DIR/feature-gate-async-fn-in-dyn-trait.rs:9:7
|
LL | x.bar().await;
| ^^^ `Foo` cannot be made into an object
|
note: for a trait to be "dyn-compatible" 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/feature-gate-async-fn-in-dyn-trait.rs:4:14
|
LL | trait Foo {
| --- this trait cannot be made into an object...
LL | async fn bar(&self);
| ^^^ ...because method `bar` is `async`
= help: consider moving `bar` to another trait

error[E0038]: the trait `Foo` cannot be made into an object
--> $DIR/feature-gate-async-fn-in-dyn-trait.rs:9:5
|
LL | x.bar().await;
| ^^^^^^^ `Foo` cannot be made into an object
|
note: for a trait to be "dyn-compatible" 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/feature-gate-async-fn-in-dyn-trait.rs:4:14
|
LL | trait Foo {
| --- this trait cannot be made into an object...
LL | async fn bar(&self);
| ^^^ ...because method `bar` is `async`
= help: consider moving `bar` to another trait

error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0038`.

0 comments on commit a9fc2e2

Please sign in to comment.