Rollup merge of #104716 - lcnr:selection-candidate, r=jackh726

move 2 candidates into builtin candidate

having separate candidates for these isn't too helpful i think

r? types

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

@@ -282,10 +282,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 self.assemble_builtin_bound_candidates(copy_conditions, &mut candidates);
             } else if lang_items.discriminant_kind_trait() == Some(def_id) {
                 // `DiscriminantKind` is automatically implemented for every type.
-                candidates.vec.push(DiscriminantKindCandidate);
+                candidates.vec.push(BuiltinCandidate { has_nested: false });
             } else if lang_items.pointee_trait() == Some(def_id) {
                 // `Pointee` is automatically implemented for every type.
-                candidates.vec.push(PointeeCandidate);
+                candidates.vec.push(BuiltinCandidate { has_nested: false });
             } else if lang_items.sized_trait() == Some(def_id) {
                 // Sized is never implementable by end-users, it is
                 // always automatically computed.

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

@@ -22,12 +22,11 @@ use crate::traits::util::{self, closure_trait_ref_and_return_type, predicate_for
 use crate::traits::{
     BuiltinDerivedObligation, ImplDerivedObligation, ImplDerivedObligationCause, ImplSource,
     ImplSourceAutoImplData, ImplSourceBuiltinData, ImplSourceClosureData,
-    ImplSourceConstDestructData, ImplSourceDiscriminantKindData, ImplSourceFnPointerData,
-    ImplSourceFutureData, ImplSourceGeneratorData, ImplSourceObjectData, ImplSourcePointeeData,
-    ImplSourceTraitAliasData, ImplSourceTraitUpcastingData, ImplSourceUserDefinedData, Normalized,
-    ObjectCastObligation, Obligation, ObligationCause, OutputTypeParameterMismatch,
-    PredicateObligation, Selection, SelectionError, TraitNotObjectSafe, TraitObligation,
-    Unimplemented, VtblSegment,
+    ImplSourceConstDestructData, ImplSourceFnPointerData, ImplSourceFutureData,
+    ImplSourceGeneratorData, ImplSourceObjectData, ImplSourceTraitAliasData,
+    ImplSourceTraitUpcastingData, ImplSourceUserDefinedData, Normalized, ObjectCastObligation,
+    Obligation, ObligationCause, OutputTypeParameterMismatch, PredicateObligation, Selection,
+    SelectionError, TraitNotObjectSafe, TraitObligation, Unimplemented, VtblSegment,
 };
 
 use super::BuiltinImplConditions;
@@ -100,12 +99,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 ImplSource::FnPointer(data)
             }
 
-            DiscriminantKindCandidate => {
-                ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData)
-            }
-
-            PointeeCandidate => ImplSource::Pointee(ImplSourcePointeeData),
-
             TraitAliasCandidate => {
                 let data = self.confirm_trait_alias_candidate(obligation);
                 ImplSource::TraitAlias(data)

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

@@ -1569,20 +1569,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             (TransmutabilityCandidate, _) | (_, TransmutabilityCandidate) => false,
 
             // (*)
-            (
-                BuiltinCandidate { has_nested: false }
-                | DiscriminantKindCandidate
-                | PointeeCandidate
-                | ConstDestructCandidate(_),
-                _,
-            ) => true,
-            (
-                _,
-                BuiltinCandidate { has_nested: false }
-                | DiscriminantKindCandidate
-                | PointeeCandidate
-                | ConstDestructCandidate(_),
-            ) => false,
+            (BuiltinCandidate { has_nested: false } | ConstDestructCandidate(_), _) => true,
+            (_, BuiltinCandidate { has_nested: false } | ConstDestructCandidate(_)) => false,
 
             (ParamCandidate(other), ParamCandidate(victim)) => {
                 let same_except_bound_vars = other.skip_binder().trait_ref