diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
index 971d3a81102..e27143f1396 100644
--- a/compiler/rustc_trait_selection/src/traits/coherence.rs
+++ b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -6,7 +6,7 @@
use std::fmt::Debug;
-use rustc_data_structures::fx::FxIndexSet;
+use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
use rustc_errors::{Diag, EmissionGuarantee};
use rustc_hir::def::DefKind;
use rustc_hir::def_id::DefId;
@@ -116,28 +116,39 @@ pub fn overlapping_impls(
return None;
}
- let _overlap_with_bad_diagnostics = overlap(
- tcx,
- TrackAmbiguityCauses::No,
- skip_leak_check,
- impl1_def_id,
- impl2_def_id,
- overlap_mode,
- )?;
+ if tcx.next_trait_solver_in_coherence() {
+ overlap(
+ tcx,
+ TrackAmbiguityCauses::Yes,
+ skip_leak_check,
+ impl1_def_id,
+ impl2_def_id,
+ overlap_mode,
+ )
+ } else {
+ let _overlap_with_bad_diagnostics = overlap(
+ tcx,
+ TrackAmbiguityCauses::No,
+ skip_leak_check,
+ impl1_def_id,
+ impl2_def_id,
+ overlap_mode,
+ )?;
- // In the case where we detect an error, run the check again, but
- // this time tracking intercrate ambiguity causes for better
- // diagnostics. (These take time and can lead to false errors.)
- let overlap = overlap(
- tcx,
- TrackAmbiguityCauses::Yes,
- skip_leak_check,
- impl1_def_id,
- impl2_def_id,
- overlap_mode,
- )
- .unwrap();
- Some(overlap)
+ // In the case where we detect an error, run the check again, but
+ // this time tracking intercrate ambiguity causes for better
+ // diagnostics. (These take time and can lead to false errors.)
+ let overlap = overlap(
+ tcx,
+ TrackAmbiguityCauses::Yes,
+ skip_leak_check,
+ impl1_def_id,
+ impl2_def_id,
+ overlap_mode,
+ )
+ .unwrap();
+ Some(overlap)
+ }
}
fn fresh_impl_header<'tcx>(infcx: &InferCtxt<'tcx>, impl_def_id: DefId) -> ty::ImplHeader<'tcx> {
@@ -615,6 +626,7 @@ fn compute_intercrate_ambiguity_causes<'tcx>(
}
struct AmbiguityCausesVisitor<'a, 'tcx> {
+ cache: FxHashSet<Goal<'tcx, ty::Predicate<'tcx>>>,
causes: &'a mut FxIndexSet<IntercrateAmbiguityCause<'tcx>>,
}
@@ -624,6 +636,10 @@ impl<'a, 'tcx> ProofTreeVisitor<'tcx> for AmbiguityCausesVisitor<'a, 'tcx> {
}
fn visit_goal(&mut self, goal: &InspectGoal<'_, 'tcx>) {
+ if !self.cache.insert(goal.goal()) {
+ return;
+ }
+
let infcx = goal.infcx();
for cand in goal.candidates() {
cand.visit_nested_in_probe(self);
@@ -748,5 +764,10 @@ fn search_ambiguity_causes<'tcx>(
goal: Goal<'tcx, ty::Predicate<'tcx>>,
causes: &mut FxIndexSet<IntercrateAmbiguityCause<'tcx>>,
) {
- infcx.probe(|_| infcx.visit_proof_tree(goal, &mut AmbiguityCausesVisitor { causes }));
+ infcx.probe(|_| {
+ infcx.visit_proof_tree(goal, &mut AmbiguityCausesVisitor {
+ cache: Default::default(),
+ causes,
+ })
+ });
}
diff --git a/tests/ui/coherence/occurs-check/associated-type.next.stderr b/tests/ui/coherence/occurs-check/associated-type.next.stderr
index 466b991471e..25f9523f4e4 100644
--- a/tests/ui/coherence/occurs-check/associated-type.next.stderr
+++ b/tests/ui/coherence/occurs-check/associated-type.next.stderr
@@ -1,7 +1,5 @@
WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1), "'a")], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1), "'a")], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
- WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1), "'a")], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
- WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1), "'a")], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
error[E0119]: conflicting implementations of trait `Overlap<for<'a> fn(&'a (), ())>` for type `for<'a> fn(&'a (), ())`
--> $DIR/associated-type.rs:32:1
|
diff --git a/tests/ui/coherence/occurs-check/associated-type.old.stderr b/tests/ui/coherence/occurs-check/associated-type.old.stderr
index 1e0345f4ec0..e091ddcacb2 100644
--- a/tests/ui/coherence/occurs-check/associated-type.old.stderr
+++ b/tests/ui/coherence/occurs-check/associated-type.old.stderr
@@ -1,7 +1,5 @@
WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1), "'a")], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1), "'a")], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
- WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1), "'a")], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
- WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1), "'a")], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
error[E0119]: conflicting implementations of trait `Overlap<for<'a> fn(&'a (), ())>` for type `for<'a> fn(&'a (), ())`
--> $DIR/associated-type.rs:32:1
|
diff --git a/tests/ui/traits/next-solver/coherence/ambiguity-causes-visitor-hang.rs b/tests/ui/traits/next-solver/coherence/ambiguity-causes-visitor-hang.rs
new file mode 100644
index 00000000000..54854b1b8a5
--- /dev/null
+++ b/tests/ui/traits/next-solver/coherence/ambiguity-causes-visitor-hang.rs
@@ -0,0 +1,56 @@
+// Computing the ambiguity causes for the overlap ended up
+// causing an exponential blowup when recursing into the normalization
+// goals for `<Box<?t> as RecursiveSuper>::Assoc`. This test
+// takes multiple minutes when doing so and less than a second
+// otherwise.
+
+//@ compile-flags: -Znext-solver=coherence
+
+trait RecursiveSuper:
+ Super<
+ A0 = Self::Assoc,
+ A1 = Self::Assoc,
+ A2 = Self::Assoc,
+ A3 = Self::Assoc,
+ A4 = Self::Assoc,
+ A5 = Self::Assoc,
+ A6 = Self::Assoc,
+ A7 = Self::Assoc,
+ A8 = Self::Assoc,
+ A9 = Self::Assoc,
+ A10 = Self::Assoc,
+ A11 = Self::Assoc,
+ A12 = Self::Assoc,
+ A13 = Self::Assoc,
+ A14 = Self::Assoc,
+ A15 = Self::Assoc,
+ >
+{
+ type Assoc;
+}
+
+trait Super {
+ type A0;
+ type A1;
+ type A2;
+ type A3;
+ type A4;
+ type A5;
+ type A6;
+ type A7;
+ type A8;
+ type A9;
+ type A10;
+ type A11;
+ type A12;
+ type A13;
+ type A14;
+ type A15;
+}
+
+trait Overlap {}
+impl<T: RecursiveSuper> Overlap for T {}
+impl<T> Overlap for Box<T> {}
+//~^ ERROR conflicting implementations of trait `Overlap` for type `Box<_>`
+
+fn main() {}
diff --git a/tests/ui/traits/next-solver/coherence/ambiguity-causes-visitor-hang.stderr b/tests/ui/traits/next-solver/coherence/ambiguity-causes-visitor-hang.stderr
new file mode 100644
index 00000000000..3731dc5b74e
--- /dev/null
+++ b/tests/ui/traits/next-solver/coherence/ambiguity-causes-visitor-hang.stderr
@@ -0,0 +1,14 @@
+error[E0119]: conflicting implementations of trait `Overlap` for type `Box<_>`
+ --> $DIR/ambiguity-causes-visitor-hang.rs:53:1
+ |
+LL | impl<T: RecursiveSuper> Overlap for T {}
+ | ------------------------------------- first implementation here
+LL | impl<T> Overlap for Box<T> {}
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Box<_>`
+ |
+ = note: downstream crates may implement trait `Super` for type `std::boxed::Box<_>`
+ = note: downstream crates may implement trait `RecursiveSuper` for type `std::boxed::Box<_>`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0119`.