diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
index d13d8ff8270..0aa5b075d19 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
@@ -477,14 +477,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// This is the "trait" (meaning, the predicate "proved" by this `impl`) which provides the `Self` type we care about.
// For the purposes of this function, we hope that it is a `struct` type, and that our current `expr` is a literal of
// that struct type.
- let impl_trait_self_ref = if self.tcx.is_trait_alias(obligation.impl_def_id) {
+ let impl_trait_self_ref = if self.tcx.is_trait_alias(obligation.impl_or_alias_def_id) {
self.tcx.mk_trait_ref(
- obligation.impl_def_id,
- ty::InternalSubsts::identity_for_item(self.tcx, obligation.impl_def_id),
+ obligation.impl_or_alias_def_id,
+ ty::InternalSubsts::identity_for_item(self.tcx, obligation.impl_or_alias_def_id),
)
} else {
self.tcx
- .impl_trait_ref(obligation.impl_def_id)
+ .impl_trait_ref(obligation.impl_or_alias_def_id)
.map(|impl_def| impl_def.skip_binder())
// It is possible that this is absent. In this case, we make no progress.
.ok_or(expr)?
@@ -494,7 +494,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
let impl_self_ty: Ty<'tcx> = impl_trait_self_ref.self_ty();
let impl_predicates: ty::GenericPredicates<'tcx> =
- self.tcx.predicates_of(obligation.impl_def_id);
+ self.tcx.predicates_of(obligation.impl_or_alias_def_id);
let Some(impl_predicate_index) = obligation.impl_def_predicate_index else {
// We don't have the index, so we can only guess.
return Err(expr);
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index a35fa008a95..a805dad062e 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -1576,7 +1576,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
traits::ImplDerivedObligation(Box::new(
traits::ImplDerivedObligationCause {
derived,
- impl_def_id,
+ impl_or_alias_def_id: impl_def_id,
impl_def_predicate_index: None,
span,
},
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 54890489f8b..ef30cd55c0e 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -616,7 +616,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
ObligationCauseCode::ImplDerivedObligation(data)
if matches!(p.kind().skip_binder(), ty::PredicateKind::Clause(_)) =>
{
- Some((p, parent, data.impl_def_id, data))
+ Some((p, parent, data.impl_or_alias_def_id, data))
}
_ => None,
})
@@ -714,7 +714,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
);
}
Some(Node::Item(hir::Item {
- ident, kind: hir::ItemKind::Trait(..), ..
+ ident,
+ kind: hir::ItemKind::Trait(..) | hir::ItemKind::TraitAlias(..),
+ ..
})) => {
skip_list.insert(p);
let entry = spanned_predicates.entry(ident.span);
diff --git a/compiler/rustc_infer/src/traits/util.rs b/compiler/rustc_infer/src/traits/util.rs
index e617eb68d47..68b39c5f00f 100644
--- a/compiler/rustc_infer/src/traits/util.rs
+++ b/compiler/rustc_infer/src/traits/util.rs
@@ -158,7 +158,7 @@ impl<'tcx> Elaborator<'tcx> {
traits::ImplDerivedObligation(Box::new(
traits::ImplDerivedObligationCause {
derived,
- impl_def_id: data.def_id(),
+ impl_or_alias_def_id: data.def_id(),
impl_def_predicate_index: Some(index),
span,
},
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index c528929e756..6231dd9b6f5 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -474,7 +474,11 @@ pub enum WellFormedLoc {
#[derive(TypeVisitable, TypeFoldable)]
pub struct ImplDerivedObligationCause<'tcx> {
pub derived: DerivedObligationCause<'tcx>,
- pub impl_def_id: DefId,
+ /// The `DefId` of the `impl` that gave rise to the `derived` obligation.
+ /// If the `derived` obligation arose from a trait alias, which conceptually has a synthetic impl,
+ /// then this will be the `DefId` of that trait alias. Care should therefore be taken to handle
+ /// that exceptional case where appropriate.
+ pub impl_or_alias_def_id: DefId,
/// The index of the derived predicate in the parent impl's predicates.
pub impl_def_predicate_index: Option<usize>,
pub span: Span,
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index 45a4cf2a083..a0c67f480d0 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -3143,7 +3143,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
parent_trait_pred.print_modifiers_and_trait_path()
);
let mut is_auto_trait = false;
- match self.tcx.hir().get_if_local(data.impl_def_id) {
+ match self.tcx.hir().get_if_local(data.impl_or_alias_def_id) {
Some(Node::Item(hir::Item {
kind: hir::ItemKind::Trait(is_auto, ..),
ident,
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index 9770813e86d..0167f402610 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -1189,7 +1189,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
let cause = obligation.derived_cause(|derived| {
ImplDerivedObligation(Box::new(ImplDerivedObligationCause {
derived,
- impl_def_id,
+ impl_or_alias_def_id: impl_def_id,
impl_def_predicate_index: None,
span: obligation.cause.span,
}))
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 27feedc48be..26f869ac1fe 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -2657,7 +2657,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
let cause = cause.clone().derived_cause(parent_trait_pred, |derived| {
ImplDerivedObligation(Box::new(ImplDerivedObligationCause {
derived,
- impl_def_id: def_id,
+ impl_or_alias_def_id: def_id,
impl_def_predicate_index: Some(index),
span,
}))
diff --git a/tests/ui/traits/alias/issue-108132-unmet-trait-alias-bound-on-generic-impl.rs b/tests/ui/traits/alias/issue-108132-unmet-trait-alias-bound-on-generic-impl.rs
new file mode 100644
index 00000000000..0b1f9ab57c9
--- /dev/null
+++ b/tests/ui/traits/alias/issue-108132-unmet-trait-alias-bound-on-generic-impl.rs
@@ -0,0 +1,15 @@
+// Regression test for #108132: do not ICE upon unmet trait alias constraint in generic impl
+
+#![feature(trait_alias)]
+
+trait IteratorAlias = Iterator;
+
+struct Foo<I>(I);
+
+impl<I: IteratorAlias> Foo<I> {
+ fn f() {}
+}
+
+fn main() {
+ Foo::<()>::f() //~ trait bounds were not satisfied
+}
diff --git a/tests/ui/traits/alias/issue-108132-unmet-trait-alias-bound-on-generic-impl.stderr b/tests/ui/traits/alias/issue-108132-unmet-trait-alias-bound-on-generic-impl.stderr
new file mode 100644
index 00000000000..f1b259d5a65
--- /dev/null
+++ b/tests/ui/traits/alias/issue-108132-unmet-trait-alias-bound-on-generic-impl.stderr
@@ -0,0 +1,25 @@
+error[E0599]: the function or associated item `f` exists for struct `Foo<()>`, but its trait bounds were not satisfied
+ --> $DIR/issue-108132-unmet-trait-alias-bound-on-generic-impl.rs:14:16
+ |
+LL | struct Foo<I>(I);
+ | ------------- function or associated item `f` not found for this struct
+...
+LL | Foo::<()>::f()
+ | ^ function or associated item cannot be called on `Foo<()>` due to unsatisfied trait bounds
+ |
+note: trait bound `(): Iterator` was not satisfied
+ --> $DIR/issue-108132-unmet-trait-alias-bound-on-generic-impl.rs:5:23
+ |
+LL | trait IteratorAlias = Iterator;
+ | ------------- ^^^^^^^^ unsatisfied trait bound introduced here
+note: trait bound `(): IteratorAlias` was not satisfied
+ --> $DIR/issue-108132-unmet-trait-alias-bound-on-generic-impl.rs:9:9
+ |
+LL | impl<I: IteratorAlias> Foo<I> {
+ | ^^^^^^^^^^^^^ ------
+ | |
+ | unsatisfied trait bound introduced here
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0599`.