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Auto merge of #113215 - compiler-errors:rpitit-predicates-tweaks, r=spastorino

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Make RPITITs assume/require their parent method's predicates

Removes a FIXME from the `param_env` query where we were manually adding the parent function's predicates to the RPITIT's assumptions.

r? `@spastorino`
This commit is contained in:
bors 2023-07-04 04:24:24 +00:00
commit 0130c3a06e
8 changed files with 76 additions and 41 deletions
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19
compiler/rustc_hir_analysis/src/collect/predicates_of.rs
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@ -63,7 +63,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
use rustc_hir::*;
match tcx.opt_rpitit_info(def_id.to_def_id()) {
Some(ImplTraitInTraitData::Trait { opaque_def_id, .. }) => {
Some(ImplTraitInTraitData::Trait { opaque_def_id, fn_def_id }) => {
let opaque_ty_id = tcx.hir().local_def_id_to_hir_id(opaque_def_id.expect_local());
let opaque_ty_node = tcx.hir().get(opaque_ty_id);
let Node::Item(&Item { kind: ItemKind::OpaqueTy(OpaqueTy { lifetime_mapping, .. }), .. }) = opaque_ty_node else {
@ -71,6 +71,18 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
};
let mut predicates = Vec::new();
// RPITITs should inherit the predicates of their parent. This is
// both to ensure that the RPITITs are only instantiated when the
// parent predicates would hold, and also so that the param-env
// inherits these predicates as assumptions.
let identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
predicates.extend(
tcx.explicit_predicates_of(fn_def_id).instantiate_own(tcx, identity_substs),
);
// We also install bidirectional outlives predicates for the RPITIT
// to keep the duplicates lifetimes from opaque lowering in sync.
compute_bidirectional_outlives_predicates(
tcx,
def_id,
@ -89,12 +101,13 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
Some(ImplTraitInTraitData::Impl { fn_def_id }) => {
let assoc_item = tcx.associated_item(def_id);
let trait_assoc_predicates = tcx.predicates_of(assoc_item.trait_item_def_id.unwrap());
let trait_assoc_predicates =
tcx.explicit_predicates_of(assoc_item.trait_item_def_id.unwrap());
let impl_assoc_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
let impl_def_id = tcx.parent(fn_def_id);
let impl_trait_ref_substs =
tcx.impl_trait_ref(impl_def_id).unwrap().skip_binder().substs;
tcx.impl_trait_ref(impl_def_id).unwrap().subst_identity().substs;
let impl_assoc_substs =
impl_assoc_identity_substs.rebase_onto(tcx, impl_def_id, impl_trait_ref_substs);

4
compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
View File

@ -574,7 +574,9 @@ fn foo(&self) -> Self::T { String::new() }
let Some(hir_id) = body_owner_def_id.as_local() else {
return false;
};
let hir_id = tcx.hir().local_def_id_to_hir_id(hir_id);
let Some(hir_id) = tcx.opt_local_def_id_to_hir_id(hir_id) else {
return false;
};
// When `body_owner` is an `impl` or `trait` item, look in its associated types for
// `expected` and point at it.
let parent_id = tcx.hir().get_parent_item(hir_id);

8
compiler/rustc_metadata/src/rmeta/encoder.rs
View File

@ -1151,10 +1151,10 @@ fn should_encode_type(tcx: TyCtxt<'_>, def_id: LocalDefId, def_kind: DefKind) ->
let assoc_item = tcx.associated_item(def_id);
match assoc_item.container {
ty::AssocItemContainer::ImplContainer => true,
// FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty) always encode RPITITs,
// since we need to be able to "project" from an RPITIT associated item
// to an opaque when installing the default projection predicates in
// default trait methods with RPITITs.
// Always encode RPITITs, since we need to be able to project
// from an RPITIT associated item to an opaque when installing
// the default projection predicates in default trait methods
// with RPITITs.
ty::AssocItemContainer::TraitContainer => {
assoc_item.defaultness(tcx).has_value() || assoc_item.opt_rpitit_info.is_some()
}

19
compiler/rustc_ty_utils/src/ty.rs
View File

@ -4,8 +4,7 @@ use rustc_hir::def::DefKind;
use rustc_index::bit_set::BitSet;
use rustc_middle::query::Providers;
use rustc_middle::ty::{
self, EarlyBinder, ImplTraitInTraitData, ToPredicate, Ty, TyCtxt, TypeSuperVisitable,
TypeVisitable, TypeVisitor,
self, EarlyBinder, ToPredicate, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor,
};
use rustc_session::config::TraitSolver;
use rustc_span::def_id::{DefId, LocalDefId, CRATE_DEF_ID};
@ -120,22 +119,6 @@ fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
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, .. })
| Some(ImplTraitInTraitData::Impl { fn_def_id, .. }) = tcx.opt_rpitit_info(def_id)
{
// FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty): Should not need to add the predicates
// from the parent fn to our assumptions
predicates.extend(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

6
tests/ui/impl-trait/in-trait/issue-102140.next.stderr
View File

@ -6,11 +6,7 @@ LL | MyTrait::foo(&self)
| |
| required by a bound introduced by this call
|
help: consider removing the leading `&`-reference
|
LL - MyTrait::foo(&self)
LL + MyTrait::foo(self)
|
= help: the trait `MyTrait` is implemented for `Outer`
error[E0277]: the trait bound `&dyn MyTrait: MyTrait` is not satisfied
--> $DIR/issue-102140.rs:26:9

27
tests/ui/impl-trait/in-trait/wf-bounds.current.stderr
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@ -1,5 +1,5 @@
error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
--> $DIR/wf-bounds.rs:13:22
--> $DIR/wf-bounds.rs:17:22
|
LL | fn nya() -> impl Wf<Vec<[u8]>>;
| ^^^^^^^^^^^^^ doesn't have a size known at compile-time
@ -9,14 +9,14 @@ note: required by a bound in `Vec`
--> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
--> $DIR/wf-bounds.rs:16:23
--> $DIR/wf-bounds.rs:20:23
|
LL | fn nya2() -> impl Wf<[u8]>;
| ^^^^^^^^ doesn't have a size known at compile-time
|
= help: the trait `Sized` is not implemented for `[u8]`
note: required by a bound in `Wf`
--> $DIR/wf-bounds.rs:8:10
--> $DIR/wf-bounds.rs:10:10
|
LL | trait Wf<T> {
| ^ required by this bound in `Wf`
@ -26,7 +26,7 @@ LL | trait Wf<T: ?Sized> {
| ++++++++
error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
--> $DIR/wf-bounds.rs:19:44
--> $DIR/wf-bounds.rs:23:44
|
LL | fn nya3() -> impl Wf<(), Output = impl Wf<Vec<[u8]>>>;
| ^^^^^^^^^^^^^ doesn't have a size known at compile-time
@ -35,6 +35,23 @@ LL | fn nya3() -> impl Wf<(), Output = impl Wf<Vec<[u8]>>>;
note: required by a bound in `Vec`
--> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
error: aborting due to 3 previous errors
error[E0277]: `T` doesn't implement `std::fmt::Display`
--> $DIR/wf-bounds.rs:26:26
|
LL | fn nya4<T>() -> impl Wf<NeedsDisplay<T>>;
| ^^^^^^^^^^^^^^^^^^^ `T` cannot be formatted with the default formatter
|
= note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
note: required by a bound in `NeedsDisplay`
--> $DIR/wf-bounds.rs:14:24
|
LL | struct NeedsDisplay<T: Display>(T);
| ^^^^^^^ required by this bound in `NeedsDisplay`
help: consider restricting type parameter `T`
|
LL | fn nya4<T: std::fmt::Display>() -> impl Wf<NeedsDisplay<T>>;
| +++++++++++++++++++
error: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0277`.

27
tests/ui/impl-trait/in-trait/wf-bounds.next.stderr
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@ -1,5 +1,5 @@
error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
--> $DIR/wf-bounds.rs:13:22
--> $DIR/wf-bounds.rs:17:22
|
LL | fn nya() -> impl Wf<Vec<[u8]>>;
| ^^^^^^^^^^^^^ doesn't have a size known at compile-time
@ -9,14 +9,14 @@ note: required by a bound in `Vec`
--> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
--> $DIR/wf-bounds.rs:16:23
--> $DIR/wf-bounds.rs:20:23
|
LL | fn nya2() -> impl Wf<[u8]>;
| ^^^^^^^^ doesn't have a size known at compile-time
|
= help: the trait `Sized` is not implemented for `[u8]`
note: required by a bound in `Wf`
--> $DIR/wf-bounds.rs:8:10
--> $DIR/wf-bounds.rs:10:10
|
LL | trait Wf<T> {
| ^ required by this bound in `Wf`
@ -26,7 +26,7 @@ LL | trait Wf<T: ?Sized> {
| ++++++++
error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
--> $DIR/wf-bounds.rs:19:44
--> $DIR/wf-bounds.rs:23:44
|
LL | fn nya3() -> impl Wf<(), Output = impl Wf<Vec<[u8]>>>;
| ^^^^^^^^^^^^^ doesn't have a size known at compile-time
@ -35,6 +35,23 @@ LL | fn nya3() -> impl Wf<(), Output = impl Wf<Vec<[u8]>>>;
note: required by a bound in `Vec`
--> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
error: aborting due to 3 previous errors
error[E0277]: `T` doesn't implement `std::fmt::Display`
--> $DIR/wf-bounds.rs:26:26
|
LL | fn nya4<T>() -> impl Wf<NeedsDisplay<T>>;
| ^^^^^^^^^^^^^^^^^^^ `T` cannot be formatted with the default formatter
|
= note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
note: required by a bound in `NeedsDisplay`
--> $DIR/wf-bounds.rs:14:24
|
LL | struct NeedsDisplay<T: Display>(T);
| ^^^^^^^ required by this bound in `NeedsDisplay`
help: consider restricting type parameter `T`
|
LL | fn nya4<T: std::fmt::Display>() -> impl Wf<NeedsDisplay<T>>;
| +++++++++++++++++++
error: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0277`.

7
tests/ui/impl-trait/in-trait/wf-bounds.rs
View File

@ -5,10 +5,14 @@
#![feature(return_position_impl_trait_in_trait)]
#![allow(incomplete_features)]
use std::fmt::Display;
trait Wf<T> {
type Output;
}
struct NeedsDisplay<T: Display>(T);
trait Uwu {
fn nya() -> impl Wf<Vec<[u8]>>;
//~^ ERROR the size for values of type `[u8]` cannot be known at compilation time
@ -18,6 +22,9 @@ trait Uwu {
fn nya3() -> impl Wf<(), Output = impl Wf<Vec<[u8]>>>;
//~^ ERROR the size for values of type `[u8]` cannot be known at compilation time
fn nya4<T>() -> impl Wf<NeedsDisplay<T>>;
//~^ ERROR `T` doesn't implement `std::fmt::Display`
}
fn main() {}