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Revert "Rollup merge of #92006 - oli-obk:welcome_opaque_types_into_th… #92928

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Revert "Rollup merge of #92006 - oli-obk:welcome_opaque_types_into_th… #92928

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20 changes: 4 additions & 16 deletions compiler/rustc_infer/src/infer/opaque_types.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -555,22 +555,6 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> {
let predicate = predicate.subst(tcx, substs);
debug!(?predicate);

let predicate = predicate.fold_with(&mut BottomUpFolder {
tcx,
ty_op: |ty| match *ty.kind() {
// Replace all other mentions of the same opaque type with the hidden type,
// as the bounds must hold on the hidden type after all.
ty::Opaque(def_id2, substs2) if def_id == def_id2 && substs == substs2 => {
ty_var
}
// Instantiate nested instances of `impl Trait`.
ty::Opaque(..) => self.instantiate_opaque_types_in_map(ty),
_ => ty,
},
lt_op: |lt| lt,
ct_op: |ct| ct,
});

// We can't normalize associated types from `rustc_infer`, but we can eagerly register inference variables for them.
let predicate = predicate.fold_with(&mut BottomUpFolder {
tcx,
Expand All @@ -595,6 +579,10 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> {
return tcx.ty_error();
}
}
// Change the predicate to refer to the type variable,
// which will be the concrete type instead of the opaque type.
// This also instantiates nested instances of `impl Trait`.
let predicate = self.instantiate_opaque_types_in_map(predicate);

let cause =
traits::ObligationCause::new(self.value_span, self.body_id, traits::OpaqueType);
Expand Down
61 changes: 19 additions & 42 deletions compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs
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Expand Up @@ -4,9 +4,7 @@ use crate::infer::canonical::{
use crate::infer::{InferCtxt, InferOk};
use crate::traits::query::Fallible;
use crate::traits::ObligationCause;
use rustc_infer::infer::canonical::{Canonical, Certainty};
use rustc_infer::traits::query::NoSolution;
use rustc_infer::traits::PredicateObligations;
use rustc_infer::infer::canonical::Canonical;
use rustc_middle::ty::fold::TypeFoldable;
use rustc_middle::ty::{ParamEnvAnd, TyCtxt};
use std::fmt;
Expand All @@ -19,6 +17,7 @@ pub mod implied_outlives_bounds;
pub mod normalize;
pub mod outlives;
pub mod prove_predicate;
use self::prove_predicate::ProvePredicate;
pub mod subtype;

pub use rustc_middle::traits::query::type_op::*;
Expand Down Expand Up @@ -81,14 +80,9 @@ pub trait QueryTypeOp<'tcx>: fmt::Debug + Copy + TypeFoldable<'tcx> + 'tcx {
query_key: ParamEnvAnd<'tcx, Self>,
infcx: &InferCtxt<'_, 'tcx>,
output_query_region_constraints: &mut QueryRegionConstraints<'tcx>,
) -> Fallible<(
Self::QueryResponse,
Option<Canonical<'tcx, ParamEnvAnd<'tcx, Self>>>,
PredicateObligations<'tcx>,
Certainty,
)> {
) -> Fallible<(Self::QueryResponse, Option<Canonical<'tcx, ParamEnvAnd<'tcx, Self>>>)> {
if let Some(result) = QueryTypeOp::try_fast_path(infcx.tcx, &query_key) {
return Ok((result, None, vec![], Certainty::Proven));
return Ok((result, None));
}

// FIXME(#33684) -- We need to use
Expand All @@ -110,7 +104,20 @@ pub trait QueryTypeOp<'tcx>: fmt::Debug + Copy + TypeFoldable<'tcx> + 'tcx {
output_query_region_constraints,
)?;

Ok((value, Some(canonical_self), obligations, canonical_result.value.certainty))
// Typically, instantiating NLL query results does not
// create obligations. However, in some cases there
// are unresolved type variables, and unify them *can*
// create obligations. In that case, we have to go
// fulfill them. We do this via a (recursive) query.
for obligation in obligations {
let ((), _) = ProvePredicate::fully_perform_into(
obligation.param_env.and(ProvePredicate::new(obligation.predicate)),
infcx,
output_query_region_constraints,
)?;
}

Ok((value, Some(canonical_self)))
}
}

Expand All @@ -122,39 +129,9 @@ where

fn fully_perform(self, infcx: &InferCtxt<'_, 'tcx>) -> Fallible<TypeOpOutput<'tcx, Self>> {
let mut region_constraints = QueryRegionConstraints::default();
let (output, canonicalized_query, mut obligations, _) =
let (output, canonicalized_query) =
Q::fully_perform_into(self, infcx, &mut region_constraints)?;

// Typically, instantiating NLL query results does not
// create obligations. However, in some cases there
// are unresolved type variables, and unify them *can*
// create obligations. In that case, we have to go
// fulfill them. We do this via a (recursive) query.
while !obligations.is_empty() {
trace!("{:#?}", obligations);
let mut progress = false;
for obligation in std::mem::take(&mut obligations) {
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I wonder if this hurts perf. We create a new Vec when we take, so we have to reallocate when new obligations are pushed.

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trying this out in #93007

let obligation = infcx.resolve_vars_if_possible(obligation);
match ProvePredicate::fully_perform_into(
obligation.param_env.and(ProvePredicate::new(obligation.predicate)),
infcx,
&mut region_constraints,
) {
Ok(((), _, new, certainty)) => {
obligations.extend(new);
progress = true;
if let Certainty::Ambiguous = certainty {
obligations.push(obligation);
}
}
Err(_) => obligations.push(obligation),
}
}
if !progress {
return Err(NoSolution);
}
}

// Promote the final query-region-constraints into a
// (optional) ref-counted vector:
let region_constraints =
Expand Down
4 changes: 4 additions & 0 deletions src/test/ui/type-alias-impl-trait/bound_reduction2.rs
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Expand Up @@ -15,5 +15,9 @@ impl<W> Trait<W> for () {}

fn foo_desugared<T: TraitWithAssoc>(_: T) -> Foo<T::Assoc> {
//~^ ERROR non-defining opaque type use in defining scope
//~| ERROR non-defining opaque type use in defining scope
//~| ERROR non-defining opaque type use in defining scope
//~| ERROR `T` is part of concrete type but not used in parameter list
//~| ERROR `T` is part of concrete type but not used in parameter list
()
}
56 changes: 53 additions & 3 deletions src/test/ui/type-alias-impl-trait/bound_reduction2.stderr
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@@ -1,20 +1,70 @@
error: type parameter `T` is part of concrete type but not used in parameter list for the `impl Trait` type alias
--> $DIR/bound_reduction2.rs:16:60
|
LL | fn foo_desugared<T: TraitWithAssoc>(_: T) -> Foo<T::Assoc> {
| ____________________________________________________________^
LL | |
LL | |
LL | |
... |
LL | | ()
LL | | }
| |_^

error: type parameter `T` is part of concrete type but not used in parameter list for the `impl Trait` type alias
--> $DIR/bound_reduction2.rs:16:60
|
LL | fn foo_desugared<T: TraitWithAssoc>(_: T) -> Foo<T::Assoc> {
| ____________________________________________________________^
LL | |
LL | |
LL | |
... |
LL | | ()
LL | | }
| |_^

error: non-defining opaque type use in defining scope
--> $DIR/bound_reduction2.rs:16:46
--> $DIR/bound_reduction2.rs:16:1
|
LL | fn foo_desugared<T: TraitWithAssoc>(_: T) -> Foo<T::Assoc> {
| ^^^^^^^^^^^^^
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: used non-generic type `<T as TraitWithAssoc>::Assoc` for generic parameter
--> $DIR/bound_reduction2.rs:9:10
|
LL | type Foo<V> = impl Trait<V>;
| ^

error: non-defining opaque type use in defining scope
--> $DIR/bound_reduction2.rs:16:1
|
LL | fn foo_desugared<T: TraitWithAssoc>(_: T) -> Foo<T::Assoc> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: used non-generic type `_` for generic parameter
--> $DIR/bound_reduction2.rs:9:10
|
LL | type Foo<V> = impl Trait<V>;
| ^

error: non-defining opaque type use in defining scope
--> $DIR/bound_reduction2.rs:16:1
|
LL | fn foo_desugared<T: TraitWithAssoc>(_: T) -> Foo<T::Assoc> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: used non-generic type `_` for generic parameter
--> $DIR/bound_reduction2.rs:9:10
|
LL | type Foo<V> = impl Trait<V>;
| ^

error: could not find defining uses
--> $DIR/bound_reduction2.rs:9:15
|
LL | type Foo<V> = impl Trait<V>;
| ^^^^^^^^^^^^^

error: aborting due to 2 previous errors
error: aborting due to 6 previous errors