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Don't install default opaque projection predicates in RPITIT associated type's param-env

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This commit is contained in:
Michael Goulet 2023-03-16 01:11:04 +00:00
parent 0949da8f4e
commit ff7c3b854d
12 changed files with 78 additions and 21 deletions
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28
compiler/rustc_hir_analysis/src/check/wfcheck.rs
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@ -1545,21 +1545,27 @@ fn check_return_position_impl_trait_in_trait_bounds<'tcx>(
if let Some(assoc_item) = tcx.opt_associated_item(fn_def_id.to_def_id())
&& assoc_item.container == ty::AssocItemContainer::TraitContainer
{
// FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty): Even with the new lowering
// strategy, we can't just call `check_associated_item` on the new RPITITs,
// because tests like `tests/ui/async-await/in-trait/implied-bounds.rs` will fail.
// That's because we need to check that the bounds of the RPITIT hold using
// the special substs that we create during opaque type lowering, otherwise we're
// getting a bunch of early bound and free regions mixed up... Haven't looked too
// deep into this, though.
for arg in fn_output.walk() {
if let ty::GenericArgKind::Type(ty) = arg.unpack()
&& let ty::Alias(ty::Opaque, proj) = ty.kind()
// FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty) we should just check
// `tcx.def_kind(proj.def_id) == DefKind::ImplTraitPlaceholder`. Right now
// `check_associated_type_bounds` is not called for RPITITs synthesized as
// associated types. See `check_mod_type_wf` to see how synthesized associated
// types are missed due to iterating over HIR.
&& tcx.is_impl_trait_in_trait(proj.def_id)
&& tcx.impl_trait_in_trait_parent_fn(proj.def_id) == fn_def_id.to_def_id()
// RPITITs are always eagerly normalized into opaques, so always look for an
// opaque here.
&& let ty::Alias(ty::Opaque, opaque_ty) = ty.kind()
&& let Some(opaque_def_id) = opaque_ty.def_id.as_local()
&& let opaque = tcx.hir().expect_item(opaque_def_id).expect_opaque_ty()
&& let hir::OpaqueTyOrigin::FnReturn(source) | hir::OpaqueTyOrigin::AsyncFn(source) = opaque.origin
&& source == fn_def_id
{
let span = tcx.def_span(proj.def_id);
let bounds = wfcx.tcx().explicit_item_bounds(proj.def_id);
let span = tcx.def_span(opaque_ty.def_id);
let bounds = wfcx.tcx().explicit_item_bounds(opaque_ty.def_id);
let wf_obligations = bounds.iter().flat_map(|&(bound, bound_span)| {
let bound = ty::EarlyBinder(bound).subst(tcx, proj.substs);
let bound = ty::EarlyBinder(bound).subst(tcx, opaque_ty.substs);
let normalized_bound = wfcx.normalize(span, None, bound);
traits::wf::predicate_obligations(
wfcx.infcx,

22
compiler/rustc_ty_utils/src/ty.rs
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@ -117,16 +117,22 @@ fn adt_sized_constraint(tcx: TyCtxt<'_>, def_id: DefId) -> &[Ty<'_>] {
/// See `ParamEnv` struct definition for details.
fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
// When computing the param_env of an RPITIT, copy param_env of the containing function. The
// synthesized associated type doesn't have extra predicates to assume.
if let Some(ImplTraitInTraitData::Trait { fn_def_id, .. }) = tcx.opt_rpitit_info(def_id) {
return tcx.param_env(fn_def_id);
}
// Compute the bounds on Self and the type parameters.
let ty::InstantiatedPredicates { mut predicates, .. } =
tcx.predicates_of(def_id).instantiate_identity(tcx);
// When computing the param_env of an RPITIT, use predicates of the containing function,
// *except* for the additional assumption that the RPITIT normalizes to the trait method's
// default opaque type. This is needed to properly check the item bounds of the assoc
// type hold (`check_type_bounds`), since that method already installs a similar projection
// bound, so they will conflict.
// FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty): I don't like this, we should
// at least be making sure that the generics in RPITITs and their parent fn don't
// get out of alignment, or else we do actually need to substitute these predicates.
if let Some(ImplTraitInTraitData::Trait { fn_def_id, .. }) = tcx.opt_rpitit_info(def_id) {
predicates = tcx.predicates_of(fn_def_id).instantiate_identity(tcx).predicates;
}
// Finally, we have to normalize the bounds in the environment, in
// case they contain any associated type projections. This process
// can yield errors if the put in illegal associated types, like
@ -160,7 +166,9 @@ fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
}
let local_did = def_id.as_local();
let hir_id = local_did.map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id));
// FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty): This isn't correct for
// RPITITs in const trait fn.
let hir_id = local_did.and_then(|def_id| tcx.opt_local_def_id_to_hir_id(def_id));
// FIXME(consts): This is not exactly in line with the constness query.
let constness = match hir_id {

2
tests/ui/impl-trait/in-trait/box-coerce-span-in-default.stderr → tests/ui/impl-trait/in-trait/box-coerce-span-in-default.current.stderr
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@ -1,5 +1,5 @@
warning: the feature `return_position_impl_trait_in_trait` is incomplete and may not be safe to use and/or cause compiler crashes
--> $DIR/box-coerce-span-in-default.rs:3:12
--> $DIR/box-coerce-span-in-default.rs:5:12
|
LL | #![feature(return_position_impl_trait_in_trait)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

11
tests/ui/impl-trait/in-trait/box-coerce-span-in-default.next.stderr Normal file
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@ -0,0 +1,11 @@
warning: the feature `return_position_impl_trait_in_trait` is incomplete and may not be safe to use and/or cause compiler crashes
--> $DIR/box-coerce-span-in-default.rs:5:12
|
LL | #![feature(return_position_impl_trait_in_trait)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: see issue #91611 <https://github.com/rust-lang/rust/issues/91611> for more information
= note: `#[warn(incomplete_features)]` on by default
warning: 1 warning emitted

2
tests/ui/impl-trait/in-trait/box-coerce-span-in-default.rs
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@ -1,4 +1,6 @@
// check-pass
// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
// revisions: current next
#![feature(return_position_impl_trait_in_trait)]
//~^ WARN the feature `return_position_impl_trait_in_trait` is incomplete

2
tests/ui/impl-trait/in-trait/default-body-type-err-2.stderr → tests/ui/impl-trait/in-trait/default-body-type-err-2.current.stderr
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@ -1,5 +1,5 @@
error[E0308]: mismatched types
--> $DIR/default-body-type-err-2.rs:8:9
--> $DIR/default-body-type-err-2.rs:10:9
|
LL | 42
| ^^- help: try using a conversion method: `.to_string()`

11
tests/ui/impl-trait/in-trait/default-body-type-err-2.next.stderr Normal file
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@ -0,0 +1,11 @@
error[E0308]: mismatched types
--> $DIR/default-body-type-err-2.rs:10:9
|
LL | 42
| ^^- help: try using a conversion method: `.to_string()`
| |
| expected `String`, found integer
error: aborting due to previous error
For more information about this error, try `rustc --explain E0308`.

2
tests/ui/impl-trait/in-trait/default-body-type-err-2.rs
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@ -1,4 +1,6 @@
// edition:2021
// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
// revisions: current next
#![allow(incomplete_features)]
#![feature(async_fn_in_trait)]

2
tests/ui/impl-trait/in-trait/default-body-type-err.stderr → tests/ui/impl-trait/in-trait/default-body-type-err.current.stderr
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@ -1,5 +1,5 @@
error[E0271]: type mismatch resolving `<&i32 as Deref>::Target == String`
--> $DIR/default-body-type-err.rs:7:22
--> $DIR/default-body-type-err.rs:10:22
|
LL | fn lol(&self) -> impl Deref<Target = String> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `i32`, found `String`

12
tests/ui/impl-trait/in-trait/default-body-type-err.next.stderr Normal file
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@ -0,0 +1,12 @@
error[E0271]: type mismatch resolving `<&i32 as Deref>::Target == String`
--> $DIR/default-body-type-err.rs:10:22
|
LL | fn lol(&self) -> impl Deref<Target = String> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `i32`, found `String`
LL |
LL | &1i32
| ----- return type was inferred to be `&i32` here
error: aborting due to previous error
For more information about this error, try `rustc --explain E0271`.

3
tests/ui/impl-trait/in-trait/default-body-type-err.rs
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@ -1,3 +1,6 @@
// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
// revisions: current next
#![allow(incomplete_features)]
#![feature(return_position_impl_trait_in_trait)]

2
tests/ui/impl-trait/in-trait/default-body.rs
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@ -1,5 +1,7 @@
// check-pass
// edition:2021
// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
// revisions: current next
#![feature(async_fn_in_trait, return_position_impl_trait_in_trait)]
#![allow(incomplete_features)]