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Jul 12, 2024
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[beta] backports #127618

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7ecb7f6
Update LLVM submodule
dianqk Jul 5, 2024
26c0055
instantiate higher ranked goals in candidate selection
lcnr Jul 10, 2024
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66 changes: 12 additions & 54 deletions compiler/rustc_trait_selection/src/traits/select/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -63,20 +63,6 @@ use rustc_middle::ty::print::with_no_trimmed_paths;
mod candidate_assembly;
mod confirmation;

/// Whether to consider the binder of higher ranked goals for the `leak_check` when
/// evaluating higher-ranked goals. See #119820 for more info.
///
/// While this is a bit hacky, it is necessary to match the behavior of the new solver:
/// We eagerly instantiate binders in the new solver, outside of candidate selection, so
/// the leak check inside of candidates does not consider any bound vars from the higher
/// ranked goal. However, we do exit the binder once we're completely finished with a goal,
/// so the leak-check can be used in evaluate by causing nested higher-ranked goals to fail.
#[derive(Debug, Copy, Clone)]
enum LeakCheckHigherRankedGoal {
No,
Yes,
}

#[derive(Clone, Debug, Eq, PartialEq, Hash)]
pub enum IntercrateAmbiguityCause<'tcx> {
DownstreamCrate { trait_ref: ty::TraitRef<'tcx>, self_ty: Option<Ty<'tcx>> },
Expand Down Expand Up @@ -401,10 +387,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
let mut no_candidates_apply = true;

for c in candidate_set.vec.iter() {
if self
.evaluate_candidate(stack, c, LeakCheckHigherRankedGoal::No)?
.may_apply()
{
if self.evaluate_candidate(stack, c)?.may_apply() {
no_candidates_apply = false;
break;
}
Expand Down Expand Up @@ -475,7 +458,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// is needed for specialization. Propagate overflow if it occurs.
let mut candidates = candidates
.into_iter()
.map(|c| match self.evaluate_candidate(stack, &c, LeakCheckHigherRankedGoal::No) {
.map(|c| match self.evaluate_candidate(stack, &c) {
Ok(eval) if eval.may_apply() => {
Ok(Some(EvaluatedCandidate { candidate: c, evaluation: eval }))
}
Expand Down Expand Up @@ -565,7 +548,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
obligation: &PredicateObligation<'tcx>,
) -> Result<EvaluationResult, OverflowError> {
debug_assert!(!self.infcx.next_trait_solver());
self.evaluation_probe(|this, _outer_universe| {
self.evaluation_probe(|this| {
let goal =
this.infcx.resolve_vars_if_possible((obligation.predicate, obligation.param_env));
let mut result = this.evaluate_predicate_recursively(
Expand All @@ -588,11 +571,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
/// `op`, but this can be overwritten if necessary.
fn evaluation_probe(
&mut self,
op: impl FnOnce(&mut Self, &mut ty::UniverseIndex) -> Result<EvaluationResult, OverflowError>,
op: impl FnOnce(&mut Self) -> Result<EvaluationResult, OverflowError>,
) -> Result<EvaluationResult, OverflowError> {
self.infcx.probe(|snapshot| -> Result<EvaluationResult, OverflowError> {
let mut outer_universe = self.infcx.universe();
let result = op(self, &mut outer_universe)?;
let outer_universe = self.infcx.universe();
let result = op(self)?;

match self.infcx.leak_check(outer_universe, Some(snapshot)) {
Ok(()) => {}
Expand Down Expand Up @@ -1253,7 +1236,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
}

match self.candidate_from_obligation(stack) {
Ok(Some(c)) => self.evaluate_candidate(stack, &c, LeakCheckHigherRankedGoal::Yes),
Ok(Some(c)) => self.evaluate_candidate(stack, &c),
Ok(None) => Ok(EvaluatedToAmbig),
Err(Overflow(OverflowError::Canonical)) => Err(OverflowError::Canonical),
Err(..) => Ok(EvaluatedToErr),
Expand All @@ -1278,10 +1261,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
/// Further evaluates `candidate` to decide whether all type parameters match and whether nested
/// obligations are met. Returns whether `candidate` remains viable after this further
/// scrutiny.
///
/// Depending on the value of [LeakCheckHigherRankedGoal], we may ignore the binder of the goal
/// when eagerly detecting higher ranked region errors via the `leak_check`. See that enum for
/// more info.
#[instrument(
level = "debug",
skip(self, stack),
Expand All @@ -1292,25 +1271,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
&mut self,
stack: &TraitObligationStack<'o, 'tcx>,
candidate: &SelectionCandidate<'tcx>,
leak_check_higher_ranked_goal: LeakCheckHigherRankedGoal,
) -> Result<EvaluationResult, OverflowError> {
let mut result = self.evaluation_probe(|this, outer_universe| {
// We eagerly instantiate higher ranked goals to prevent universe errors
// from impacting candidate selection. This matches the behavior of the new
// solver. This slightly weakens type inference.
//
// In case there are no unresolved type or const variables this
// should still not be necessary to select a unique impl as any overlap
// relying on a universe error from higher ranked goals should have resulted
// in an overlap error in coherence.
let p = self.infcx.enter_forall_and_leak_universe(stack.obligation.predicate);
let obligation = stack.obligation.with(this.tcx(), ty::Binder::dummy(p));
match leak_check_higher_ranked_goal {
LeakCheckHigherRankedGoal::No => *outer_universe = self.infcx.universe(),
LeakCheckHigherRankedGoal::Yes => {}
}

match this.confirm_candidate(&obligation, candidate.clone()) {
let mut result = self.evaluation_probe(|this| {
match this.confirm_candidate(stack.obligation, candidate.clone()) {
Ok(selection) => {
debug!(?selection);
this.evaluate_predicates_recursively(
Expand Down Expand Up @@ -1730,19 +1693,14 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
})
.map_err(|_| ())
}

fn where_clause_may_apply<'o>(
&mut self,
stack: &TraitObligationStack<'o, 'tcx>,
where_clause_trait_ref: ty::PolyTraitRef<'tcx>,
) -> Result<EvaluationResult, OverflowError> {
self.evaluation_probe(|this, outer_universe| {
// Eagerly instantiate higher ranked goals.
//
// See the comment in `evaluate_candidate` to see why.
let p = self.infcx.enter_forall_and_leak_universe(stack.obligation.predicate);
let obligation = stack.obligation.with(this.tcx(), ty::Binder::dummy(p));
*outer_universe = self.infcx.universe();
match this.match_where_clause_trait_ref(&obligation, where_clause_trait_ref) {
self.evaluation_probe(|this| {
match this.match_where_clause_trait_ref(stack.obligation, where_clause_trait_ref) {
Ok(obligations) => this.evaluate_predicates_recursively(stack.list(), obligations),
Err(()) => Ok(EvaluatedToErr),
}
Expand Down
2 changes: 1 addition & 1 deletion src/llvm-project
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Submodule llvm-project updated 8 files
+1 −1 llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+8 −3 llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
+28 −0 llvm/test/CodeGen/X86/addr-mode-matcher-3.ll
+12 −8 llvm/test/CodeGen/X86/sttni.ll
+205 −205 llvm/test/CodeGen/X86/var-permute-128.ll
+7 −7 llvm/test/CodeGen/X86/var-permute-256.ll
+1 −1 llvm/test/CodeGen/X86/var-permute-512.ll
+66 −0 llvm/test/Transforms/Mem2Reg/single-store.ll
23 changes: 23 additions & 0 deletions tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-1.next.stderr
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Original file line number Diff line number Diff line change
@@ -0,0 +1,23 @@
error[E0277]: the trait bound `for<'a> &'a &T: Trait` is not satisfied
--> $DIR/candidate-from-env-universe-err-1.rs:27:16
|
LL | hr_bound::<&T>();
| ^^ the trait `for<'a> Trait` is not implemented for `&'a &T`
|
note: required by a bound in `hr_bound`
--> $DIR/candidate-from-env-universe-err-1.rs:14:20
|
LL | fn hr_bound<T>()
| -------- required by a bound in this function
LL | where
LL | for<'a> &'a T: Trait,
| ^^^^^ required by this bound in `hr_bound`
help: consider removing the leading `&`-reference
|
LL - hr_bound::<&T>();
LL + hr_bound::<T>();
|

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0277`.
7 changes: 5 additions & 2 deletions tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-1.rs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,7 @@
//@ revisions: old next
//@[next] compile-flags: -Znext-solver
//@[old] check-pass

// cc #119820

trait Trait {}
Expand All @@ -21,8 +25,7 @@ where
// the leak check both candidates may apply and we prefer the
// `param_env` candidate in winnowing.
hr_bound::<&T>();
//~^ ERROR the parameter type `T` may not live long enough
//~| ERROR implementation of `Trait` is not general enough
//[next]~^ ERROR the trait bound `for<'a> &'a &T: Trait` is not satisfied
}

fn main() {}
26 changes: 0 additions & 26 deletions tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-1.stderr
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This file was deleted.

25 changes: 0 additions & 25 deletions tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-2.current.stderr
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This file was deleted.

4 changes: 2 additions & 2 deletions tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-2.next.stderr
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Original file line number Diff line number Diff line change
@@ -1,11 +1,11 @@
error[E0277]: the trait bound `for<'a> T: Trait<'a, '_>` is not satisfied
--> $DIR/candidate-from-env-universe-err-2.rs:14:5
--> $DIR/candidate-from-env-universe-err-2.rs:15:5
|
LL | impl_hr::<T>();
| ^^^^^^^^^^^^^^ the trait `for<'a> Trait<'a, '_>` is not implemented for `T`
|
note: required by a bound in `impl_hr`
--> $DIR/candidate-from-env-universe-err-2.rs:11:19
--> $DIR/candidate-from-env-universe-err-2.rs:12:19
|
LL | fn impl_hr<'b, T: for<'a> Trait<'a, 'b>>() {}
| ^^^^^^^^^^^^^^^^^^^^^ required by this bound in `impl_hr`
Expand Down
26 changes: 0 additions & 26 deletions tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-2.old.stderr
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This file was deleted.

3 changes: 1 addition & 2 deletions tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-2.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
//@ revisions: current next
//@[next] compile-flags: -Znext-solver
//@[current] check-pass

// cc #119820

Expand All @@ -13,8 +14,6 @@ fn impl_hr<'b, T: for<'a> Trait<'a, 'b>>() {}
fn not_hr<'a, T: for<'b> Trait<'a, 'b> + OtherTrait<'static>>() {
impl_hr::<T>();
//[next]~^ ERROR the trait bound `for<'a> T: Trait<'a, '_>` is not satisfied
//[current]~^^ERROR lifetime may not live long enough
//[current]~| ERROR implementation of `Trait` is not general enough
}

fn main() {}
26 changes: 4 additions & 22 deletions tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-project.current.stderr
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Original file line number Diff line number Diff line change
@@ -1,23 +1,5 @@
error: implementation of `Trait` is not general enough
--> $DIR/candidate-from-env-universe-err-project.rs:28:5
|
LL | trait_bound::<T>();
| ^^^^^^^^^^^^^^^^^^ implementation of `Trait` is not general enough
|
= note: `T` must implement `Trait<'0>`, for any lifetime `'0`...
= note: ...but it actually implements `Trait<'static>`

error: implementation of `Trait` is not general enough
--> $DIR/candidate-from-env-universe-err-project.rs:39:5
|
LL | projection_bound::<T>();
| ^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Trait` is not general enough
|
= note: `T` must implement `Trait<'0>`, for any lifetime `'0`...
= note: ...but it actually implements `Trait<'static>`

error[E0308]: mismatched types
--> $DIR/candidate-from-env-universe-err-project.rs:39:5
--> $DIR/candidate-from-env-universe-err-project.rs:38:5
|
LL | projection_bound::<T>();
| ^^^^^^^^^^^^^^^^^^^^^^^ one type is more general than the other
Expand All @@ -31,7 +13,7 @@ LL | fn projection_bound<T: for<'a> Trait<'a, Assoc = usize>>() {}
| ^^^^^^^^^^^^^

error[E0308]: mismatched types
--> $DIR/candidate-from-env-universe-err-project.rs:55:30
--> $DIR/candidate-from-env-universe-err-project.rs:53:30
|
LL | let _higher_ranked_norm: for<'a> fn(<T as Trait<'a>>::Assoc) = |_| ();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ one type is more general than the other
Expand All @@ -40,7 +22,7 @@ LL | let _higher_ranked_norm: for<'a> fn(<T as Trait<'a>>::Assoc) = |_| ();
found associated type `<T as Trait<'a>>::Assoc`

error[E0308]: mismatched types
--> $DIR/candidate-from-env-universe-err-project.rs:55:30
--> $DIR/candidate-from-env-universe-err-project.rs:53:30
|
LL | let _higher_ranked_norm: for<'a> fn(<T as Trait<'a>>::Assoc) = |_| ();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ one type is more general than the other
Expand All @@ -49,6 +31,6 @@ LL | let _higher_ranked_norm: for<'a> fn(<T as Trait<'a>>::Assoc) = |_| ();
found associated type `<T as Trait<'a>>::Assoc`
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: aborting due to 5 previous errors
error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0308`.
8 changes: 4 additions & 4 deletions tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-project.next.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@ LL | fn function1<T: Trait<'static> + for<'a> Trait<'a>>() {
| +++++++++++++++++++

error[E0277]: the trait bound `for<'a> T: Trait<'a>` is not satisfied
--> $DIR/candidate-from-env-universe-err-project.rs:39:24
--> $DIR/candidate-from-env-universe-err-project.rs:38:24
|
LL | projection_bound::<T>();
| ^ the trait `for<'a> Trait<'a>` is not implemented for `T`
Expand All @@ -31,7 +31,7 @@ LL | fn function2<T: Trait<'static, Assoc = usize> + for<'a> Trait<'a>>() {
| +++++++++++++++++++

error[E0271]: type mismatch resolving `<T as Trait<'a>>::Assoc == usize`
--> $DIR/candidate-from-env-universe-err-project.rs:39:24
--> $DIR/candidate-from-env-universe-err-project.rs:38:24
|
LL | projection_bound::<T>();
| ^ type mismatch resolving `<T as Trait<'a>>::Assoc == usize`
Expand All @@ -48,13 +48,13 @@ LL | fn projection_bound<T: for<'a> Trait<'a, Assoc = usize>>() {}
| ^^^^^^^^^^^^^ required by this bound in `projection_bound`

error: higher-ranked subtype error
--> $DIR/candidate-from-env-universe-err-project.rs:55:30
--> $DIR/candidate-from-env-universe-err-project.rs:53:30
|
LL | let _higher_ranked_norm: for<'a> fn(<T as Trait<'a>>::Assoc) = |_| ();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: higher-ranked subtype error
--> $DIR/candidate-from-env-universe-err-project.rs:55:30
--> $DIR/candidate-from-env-universe-err-project.rs:53:30
|
LL | let _higher_ranked_norm: for<'a> fn(<T as Trait<'a>>::Assoc) = |_| ();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Expand Down
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