Better names?

compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs

@@ -102,8 +102,8 @@ impl<'tcx> InherentCollect<'tcx> {
             if let Some(simp) = simplify_type(
                 self.tcx,
                 self_ty,
-                TreatParams::AsInfer,
+                TreatParams::AsCandidateKey,
-                TreatProjections::DefaultCandidate,
+                TreatProjections::AsCandidateKey,
             ) {
                 self.impls_map.incoherent_impls.entry(simp).or_default().push(impl_def_id);
             } else {
@@ -164,9 +164,12 @@ impl<'tcx> InherentCollect<'tcx> {
             }
         }
 
-        if let Some(simp) =
+        if let Some(simp) = simplify_type(
-            simplify_type(self.tcx, ty, TreatParams::AsInfer, TreatProjections::DefaultCandidate)
+            self.tcx,
-        {
+            ty,
+            TreatParams::AsCandidateKey,
+            TreatProjections::AsCandidateKey,
+        ) {
             self.impls_map.incoherent_impls.entry(simp).or_default().push(impl_def_id);
         } else {
             bug!("unexpected primitive type: {:?}", ty);

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -700,7 +700,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
     }
 
     fn assemble_inherent_candidates_for_incoherent_ty(&mut self, self_ty: Ty<'tcx>) {
-        let Some(simp) = simplify_type(self.tcx, self_ty, TreatParams::AsInfer, TreatProjections::DefaultCandidate) else {
+        let Some(simp) = simplify_type(self.tcx, self_ty, TreatParams::AsCandidateKey, TreatProjections::AsCandidateKey) else {
             bug!("unexpected incoherent type: {:?}", self_ty)
         };
         for &impl_def_id in self.tcx.incoherent_impls(simp) {

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -1258,7 +1258,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let target_ty = self
                 .autoderef(sugg_span, rcvr_ty)
                 .find(|(rcvr_ty, _)| {
-                    DeepRejectCtxt { treat_obligation_params: TreatParams::AsInfer }
+                    DeepRejectCtxt { treat_obligation_params: TreatParams::AsCandidateKey }
                         .types_may_unify(*rcvr_ty, impl_ty)
                 })
                 .map_or(impl_ty, |(ty, _)| ty)
@@ -1517,7 +1517,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             .into_iter()
             .any(|info| self.associated_value(info.def_id, item_name).is_some());
         let found_assoc = |ty: Ty<'tcx>| {
-            simplify_type(tcx, ty, TreatParams::AsInfer, TreatProjections::DefaultCandidate)
+            simplify_type(tcx, ty, TreatParams::AsCandidateKey, TreatProjections::AsCandidateKey)
                 .and_then(|simp| {
                     tcx.incoherent_impls(simp)
                         .iter()
@@ -2649,8 +2649,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             } else if let Some(simp_rcvr_ty) = simplify_type(
                 self.tcx,
                 rcvr_ty,
-                TreatParams::AsPlaceholder,
+                TreatParams::ForLookup,
-                TreatProjections::DefaultLookup,
+                TreatProjections::ForLookup,
             ) {
                 let mut potential_candidates = Vec::new();
                 let mut explicitly_negative = Vec::new();
@@ -2667,8 +2667,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             let imp_simp = simplify_type(
                                 self.tcx,
                                 imp.self_ty(),
-                                TreatParams::AsPlaceholder,
+                                TreatParams::ForLookup,
-                                TreatProjections::DefaultLookup,
+                                TreatProjections::ForLookup,
                             );
                             imp_simp.map_or(false, |s| s == simp_rcvr_ty)
                         })

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1858,8 +1858,8 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                     let simplified_self_ty = fast_reject::simplify_type(
                         self.tcx,
                         trait_ref.self_ty(),
-                        TreatParams::AsInfer,
+                        TreatParams::AsCandidateKey,
-                        TreatProjections::DefaultCandidate,
+                        TreatProjections::AsCandidateKey,
                     );
 
                     fx_hash_map

compiler/rustc_middle/src/ty/fast_reject.rs

@@ -51,9 +51,12 @@ pub enum SimplifiedType {
 /// generic parameters as if they were inference variables in that case.
 #[derive(PartialEq, Eq, Debug, Clone, Copy)]
 pub enum TreatParams {
-    /// Treat parameters as placeholders in the given environment.
+    /// Treat parameters as infer vars. This is the correct mode for caching
-    AsPlaceholder,
+    /// an impl's type for lookup.
-    AsInfer,
+    AsCandidateKey,
+    /// Treat parameters as placeholders in the given environment. This is the
+    /// correct mode for *lookup*, as during candidate selection.
+    ForLookup,
 }
 
 /// During fast-rejection, we have the choice of treating projection types
@@ -67,13 +70,13 @@ pub enum TreatProjections {
     /// We must assume that the `impl<T> Trait<T> for <T as Id>::This`
     /// can apply to all self types so we don't return a simplified type
     /// for `<T as Id>::This`.
-    DefaultCandidate,
+    AsCandidateKey,
     /// In the old solver we don't try to normalize projections
     /// when looking up impls and only access them by using the
     /// current self type. This means that if the self type is
     /// a projection which could later be normalized, we must not
     /// treat it as rigid.
-    DefaultLookup,
+    ForLookup,
     /// We can treat projections in the self type as opaque as
     /// we separately look up impls for the normalized self type.
     NextSolverLookup,
@@ -133,13 +136,13 @@ pub fn simplify_type<'tcx>(
         ty::FnPtr(f) => Some(FunctionSimplifiedType(f.skip_binder().inputs().len())),
         ty::Placeholder(..) => Some(PlaceholderSimplifiedType),
         ty::Param(_) => match treat_params {
-            TreatParams::AsPlaceholder => Some(PlaceholderSimplifiedType),
+            TreatParams::ForLookup => Some(PlaceholderSimplifiedType),
-            TreatParams::AsInfer => None,
+            TreatParams::AsCandidateKey => None,
         },
         ty::Alias(..) => match treat_projections {
-            TreatProjections::DefaultLookup if !ty.needs_infer() => Some(PlaceholderSimplifiedType),
+            TreatProjections::ForLookup if !ty.needs_infer() => Some(PlaceholderSimplifiedType),
             TreatProjections::NextSolverLookup => Some(PlaceholderSimplifiedType),
-            TreatProjections::DefaultCandidate | TreatProjections::DefaultLookup => None,
+            TreatProjections::AsCandidateKey | TreatProjections::ForLookup => None,
         },
         ty::Foreign(def_id) => Some(ForeignSimplifiedType(def_id)),
         ty::Bound(..) | ty::Infer(_) | ty::Error(_) => None,
@@ -307,8 +310,8 @@ impl DeepRejectCtxt {
             // Depending on the value of `treat_obligation_params`, we either
             // treat generic parameters like placeholders or like inference variables.
             ty::Param(_) => match self.treat_obligation_params {
-                TreatParams::AsPlaceholder => false,
+                TreatParams::ForLookup => false,
-                TreatParams::AsInfer => true,
+                TreatParams::AsCandidateKey => true,
             },
 
             ty::Infer(_) => true,
@@ -345,8 +348,8 @@ impl DeepRejectCtxt {
         let k = impl_ct.kind();
         match obligation_ct.kind() {
             ty::ConstKind::Param(_) => match self.treat_obligation_params {
-                TreatParams::AsPlaceholder => false,
+                TreatParams::ForLookup => false,
-                TreatParams::AsInfer => true,
+                TreatParams::AsCandidateKey => true,
             },
 
             // As we don't necessarily eagerly evaluate constants,

compiler/rustc_middle/src/ty/trait_def.rs

@@ -127,7 +127,7 @@ impl<'tcx> TyCtxt<'tcx> {
         self.for_each_relevant_impl_treating_projections(
             trait_def_id,
             self_ty,
-            TreatProjections::DefaultLookup,
+            TreatProjections::ForLookup,
             f,
         )
     }
@@ -156,8 +156,8 @@ impl<'tcx> TyCtxt<'tcx> {
         if let Some(simp) = fast_reject::simplify_type(
             self,
             self_ty,
-            TreatParams::AsInfer,
+            TreatParams::AsCandidateKey,
-            TreatProjections::DefaultCandidate,
+            TreatProjections::AsCandidateKey,
         ) {
             if let Some(impls) = impls.non_blanket_impls.get(&simp) {
                 return impls.iter().copied();
@@ -196,7 +196,7 @@ impl<'tcx> TyCtxt<'tcx> {
         // `T: Clone` this is incredibly useful as we would otherwise look at all the impls
         // of `Clone` for `Option<T>`, `Vec<T>`, `ConcreteType` and so on.
         if let Some(simp) =
-            fast_reject::simplify_type(self, self_ty, TreatParams::AsPlaceholder, treat_projections)
+            fast_reject::simplify_type(self, self_ty, TreatParams::ForLookup, treat_projections)
         {
             if let Some(impls) = impls.non_blanket_impls.get(&simp) {
                 for &impl_def_id in impls {
@@ -261,8 +261,8 @@ pub(super) fn trait_impls_of_provider(tcx: TyCtxt<'_>, trait_id: DefId) -> Trait
         if let Some(simplified_self_ty) = fast_reject::simplify_type(
             tcx,
             impl_self_ty,
-            TreatParams::AsInfer,
+            TreatParams::AsCandidateKey,
-            TreatProjections::DefaultCandidate,
+            TreatProjections::AsCandidateKey,
         ) {
             impls.non_blanket_impls.entry(simplified_self_ty).or_default().push(impl_def_id);
         } else {

compiler/rustc_middle/src/ty/util.rs

@@ -368,7 +368,7 @@ impl<'tcx> TyCtxt<'tcx> {
             drop_trait,
             ty,
             // FIXME: This could also be some other mode, like "unexpected"
-            TreatProjections::DefaultLookup,
+            TreatProjections::ForLookup,
             |impl_did| {
                 if let Some(item_id) = self.associated_item_def_ids(impl_did).first() {
                     if validate(self, impl_did).is_ok() {

compiler/rustc_passes/src/check_attr.rs

@@ -2215,7 +2215,7 @@ impl CheckAttrVisitor<'_> {
             // `fn(TokenStream) -> TokenStream` after some substitution of generic arguments.
             //
             // Properly checking this means pulling in additional `rustc` crates, so we don't.
-            let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsInfer };
+            let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsCandidateKey };
 
             if sig.abi != Abi::Rust {
                 tcx.sess.emit_err(errors::ProcMacroInvalidAbi {

compiler/rustc_trait_selection/src/solve/project_goals.rs

@@ -184,7 +184,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
 
         let goal_trait_ref = goal.predicate.projection_ty.trait_ref(tcx);
         let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
-        let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsPlaceholder };
+        let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
         if iter::zip(goal_trait_ref.substs, impl_trait_ref.skip_binder().substs)
             .any(|(goal, imp)| !drcx.generic_args_may_unify(goal, imp))
         {

compiler/rustc_trait_selection/src/solve/trait_goals.rs

@@ -36,7 +36,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
         let tcx = ecx.tcx();
 
         let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
-        let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsPlaceholder };
+        let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
         if iter::zip(goal.predicate.trait_ref.substs, impl_trait_ref.skip_binder().substs)
             .any(|(goal, imp)| !drcx.generic_args_may_unify(goal, imp))
         {

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -75,7 +75,7 @@ pub fn overlapping_impls(
     // Before doing expensive operations like entering an inference context, do
     // a quick check via fast_reject to tell if the impl headers could possibly
     // unify.
-    let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsInfer };
+    let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsCandidateKey };
     let impl1_ref = tcx.impl_trait_ref(impl1_def_id);
     let impl2_ref = tcx.impl_trait_ref(impl2_def_id);
     let may_overlap = match (impl1_ref, impl2_ref) {

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

@@ -1803,7 +1803,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         self.tcx.find_map_relevant_impl(
                             id,
                             proj.projection_ty.self_ty(),
-                            TreatProjections::DefaultLookup,
+                            TreatProjections::ForLookup,
                             |did| {
                                 self.tcx
                                     .associated_items(did)
@@ -2185,7 +2185,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             self.tcx.find_map_relevant_impl(
                 trait_def_id,
                 trait_ref.skip_binder().self_ty(),
-                TreatProjections::DefaultLookup,
+                TreatProjections::ForLookup,
                 Some,
             )
         };

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

@@ -784,7 +784,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 let relevant_impl = self.tcx().find_map_relevant_impl(
                     self.tcx().require_lang_item(LangItem::Drop, None),
                     obligation.predicate.skip_binder().trait_ref.self_ty(),
-                    TreatProjections::DefaultLookup,
+                    TreatProjections::ForLookup,
                     Some,
                 );
 

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

@@ -2558,7 +2558,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         // We can avoid creating type variables and doing the full
         // substitution if we find that any of the input types, when
         // simplified, do not match.
-        let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsPlaceholder };
+        let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
         iter::zip(obligation.predicate.skip_binder().trait_ref.substs, impl_trait_ref.substs)
             .any(|(obl, imp)| !drcx.generic_args_may_unify(obl, imp))
     }

compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs

@@ -52,8 +52,8 @@ impl<'tcx> ChildrenExt<'tcx> for Children {
         if let Some(st) = fast_reject::simplify_type(
             tcx,
             trait_ref.self_ty(),
-            TreatParams::AsInfer,
+            TreatParams::AsCandidateKey,
-            fast_reject::TreatProjections::DefaultCandidate,
+            TreatProjections::AsCandidateKey,
         ) {
             debug!("insert_blindly: impl_def_id={:?} st={:?}", impl_def_id, st);
             self.non_blanket_impls.entry(st).or_default().push(impl_def_id)
@@ -72,8 +72,8 @@ impl<'tcx> ChildrenExt<'tcx> for Children {
         if let Some(st) = fast_reject::simplify_type(
             tcx,
             trait_ref.self_ty(),
-            TreatParams::AsInfer,
+            TreatParams::AsCandidateKey,
-            TreatProjections::DefaultCandidate,
+            TreatProjections::AsCandidateKey,
         ) {
             debug!("remove_existing: impl_def_id={:?} st={:?}", impl_def_id, st);
             vec = self.non_blanket_impls.get_mut(&st).unwrap();
@@ -313,8 +313,8 @@ impl<'tcx> GraphExt<'tcx> for Graph {
         let simplified = fast_reject::simplify_type(
             tcx,
             trait_ref.self_ty(),
-            TreatParams::AsInfer,
+            TreatParams::AsCandidateKey,
-            TreatProjections::DefaultCandidate,
+            TreatProjections::AsCandidateKey,
         );
 
         // Descend the specialization tree, where `parent` is the current parent node.

src/librustdoc/passes/collect_intra_doc_links.rs

@@ -735,7 +735,7 @@ fn trait_impls_for<'a>(
         trace!("considering explicit impl for trait {:?}", trait_);
 
         // Look at each trait implementation to see if it's an impl for `did`
-        tcx.find_map_relevant_impl(trait_, ty, TreatProjections::DefaultLookup, |impl_| {
+        tcx.find_map_relevant_impl(trait_, ty, TreatProjections::ForLookup, |impl_| {
             let trait_ref = tcx.impl_trait_ref(impl_).expect("this is not an inherent impl");
             // Check if these are the same type.
             let impl_type = trait_ref.skip_binder().self_ty();