yeet ImplSource::TraitAlias too

compiler/rustc_middle/src/traits/mod.rs

@@ -660,9 +660,6 @@ pub enum ImplSource<'tcx, N> {
 
     /// ImplSource for trait upcasting coercion
     TraitUpcasting(ImplSourceTraitUpcastingData<N>),
-
-    /// ImplSource for a trait alias.
-    TraitAlias(ImplSourceTraitAliasData<'tcx, N>),
 }
 
 impl<'tcx, N> ImplSource<'tcx, N> {
@@ -671,7 +668,6 @@ impl<'tcx, N> ImplSource<'tcx, N> {
             ImplSource::UserDefined(i) => i.nested,
             ImplSource::Param(n, _) | ImplSource::Builtin(n) => n,
             ImplSource::Object(d) => d.nested,
-            ImplSource::TraitAlias(d) => d.nested,
             ImplSource::TraitUpcasting(d) => d.nested,
         }
     }
@@ -681,7 +677,6 @@ impl<'tcx, N> ImplSource<'tcx, N> {
             ImplSource::UserDefined(i) => &i.nested,
             ImplSource::Param(n, _) | ImplSource::Builtin(n) => &n,
             ImplSource::Object(d) => &d.nested,
-            ImplSource::TraitAlias(d) => &d.nested,
             ImplSource::TraitUpcasting(d) => &d.nested,
         }
     }
@@ -691,7 +686,6 @@ impl<'tcx, N> ImplSource<'tcx, N> {
             ImplSource::UserDefined(i) => &mut i.nested,
             ImplSource::Param(n, _) | ImplSource::Builtin(n) => n,
             ImplSource::Object(d) => &mut d.nested,
-            ImplSource::TraitAlias(d) => &mut d.nested,
             ImplSource::TraitUpcasting(d) => &mut d.nested,
         }
     }
@@ -713,11 +707,6 @@ impl<'tcx, N> ImplSource<'tcx, N> {
                 vtable_base: o.vtable_base,
                 nested: o.nested.into_iter().map(f).collect(),
             }),
-            ImplSource::TraitAlias(d) => ImplSource::TraitAlias(ImplSourceTraitAliasData {
-                alias_def_id: d.alias_def_id,
-                substs: d.substs,
-                nested: d.nested.into_iter().map(f).collect(),
-            }),
             ImplSource::TraitUpcasting(d) => {
                 ImplSource::TraitUpcasting(ImplSourceTraitUpcastingData {
                     vtable_vptr_slot: d.vtable_vptr_slot,
@@ -773,14 +762,6 @@ pub struct ImplSourceObjectData<N> {
     pub nested: Vec<N>,
 }
 
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceTraitAliasData<'tcx, N> {
-    pub alias_def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
-    pub nested: Vec<N>,
-}
-
 #[derive(Clone, Debug, PartialEq, Eq, Hash, HashStable, PartialOrd, Ord)]
 pub enum ObjectSafetyViolation {
     /// `Self: Sized` declared on the trait.

compiler/rustc_middle/src/traits/structural_impls.rs

@@ -17,8 +17,6 @@ impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSource<'tcx, N> {
                 write!(f, "ImplSourceParamData({:?}, {:?})", n, ct)
             }
 
-            super::ImplSource::TraitAlias(ref d) => write!(f, "{:?}", d),
-
             super::ImplSource::TraitUpcasting(ref d) => write!(f, "{:?}", d),
         }
     }
@@ -53,13 +51,3 @@ impl<N: fmt::Debug> fmt::Debug for traits::ImplSourceObjectData<N> {
         )
     }
 }
-
-impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceTraitAliasData<'tcx, N> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(
-            f,
-            "ImplSourceTraitAliasData(alias_def_id={:?}, substs={:?}, nested={:?})",
-            self.alias_def_id, self.substs, self.nested
-        )
-    }
-}

compiler/rustc_trait_selection/src/traits/project.rs

@@ -1721,7 +1721,6 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
         };
 
         let eligible = match &impl_source {
-            super::ImplSource::TraitAlias(_) => true,
             super::ImplSource::UserDefined(impl_data) => {
                 // We have to be careful when projecting out of an
                 // impl because of specialization. If we are not in
@@ -2013,8 +2012,7 @@ fn confirm_select_candidate<'cx, 'tcx>(
         }
         super::ImplSource::Object(_)
         | super::ImplSource::Param(..)
-        | super::ImplSource::TraitUpcasting(_)
+        | super::ImplSource::TraitUpcasting(_) => {
-        | super::ImplSource::TraitAlias(..) => {
             // we don't create Select candidates with this kind of resolution
             span_bug!(
                 obligation.cause.span,

compiler/rustc_trait_selection/src/traits/select/confirmation.rs

@@ -27,10 +27,9 @@ use crate::traits::vtable::{
 };
 use crate::traits::{
     BuiltinDerivedObligation, ImplDerivedObligation, ImplDerivedObligationCause, ImplSource,
-    ImplSourceObjectData, ImplSourceTraitAliasData, ImplSourceTraitUpcastingData,
+    ImplSourceObjectData, ImplSourceTraitUpcastingData, ImplSourceUserDefinedData, Normalized,
-    ImplSourceUserDefinedData, Normalized, Obligation, ObligationCause,
+    Obligation, ObligationCause, OutputTypeParameterMismatch, PredicateObligation, Selection,
-    OutputTypeParameterMismatch, PredicateObligation, Selection, SelectionError,
+    SelectionError, TraitNotObjectSafe, TraitObligation, Unimplemented,
-    TraitNotObjectSafe, TraitObligation, Unimplemented,
 };
 
 use super::BuiltinImplConditions;
@@ -105,7 +104,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
             TraitAliasCandidate => {
                 let data = self.confirm_trait_alias_candidate(obligation);
-                ImplSource::TraitAlias(data)
+                ImplSource::Builtin(data)
             }
 
             BuiltinObjectCandidate => {
@@ -721,10 +720,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     fn confirm_trait_alias_candidate(
         &mut self,
         obligation: &TraitObligation<'tcx>,
-    ) -> ImplSourceTraitAliasData<'tcx, PredicateObligation<'tcx>> {
+    ) -> Vec<PredicateObligation<'tcx>> {
         debug!(?obligation, "confirm_trait_alias_candidate");
 
-        let alias_def_id = obligation.predicate.def_id();
         let predicate = self.infcx.instantiate_binder_with_placeholders(obligation.predicate);
         let trait_ref = predicate.trait_ref;
         let trait_def_id = trait_ref.def_id;
@@ -741,7 +739,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
         debug!(?trait_def_id, ?trait_obligations, "trait alias obligations");
 
-        ImplSourceTraitAliasData { alias_def_id, substs, nested: trait_obligations }
+        trait_obligations
     }
 
     fn confirm_generator_candidate(

compiler/rustc_ty_utils/src/instance.rs

@@ -293,9 +293,7 @@ fn resolve_associated_item<'tcx>(
                 None
             }
         }
-        traits::ImplSource::Param(..)
+        traits::ImplSource::Param(..) | traits::ImplSource::TraitUpcasting(_) => None,
-        | traits::ImplSource::TraitAlias(..)
-        | traits::ImplSource::TraitUpcasting(_) => None,
     })
 }