Use DeepRejectCtxt to quickly reject ParamEnv candidates

compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs

@@ -90,7 +90,8 @@ impl<'tcx> InherentCollect<'tcx> {
                 }
             }
 
-            if let Some(simp) = simplify_type(self.tcx, self_ty, TreatParams::AsCandidateKey) {
+            if let Some(simp) = simplify_type(self.tcx, self_ty, TreatParams::InstantiateWithInfer)
+            {
                 self.impls_map.incoherent_impls.entry(simp).or_default().push(impl_def_id);
             } else {
                 bug!("unexpected self type: {:?}", self_ty);
@@ -129,7 +130,7 @@ impl<'tcx> InherentCollect<'tcx> {
             }
         }
 
-        if let Some(simp) = simplify_type(self.tcx, ty, TreatParams::AsCandidateKey) {
+        if let Some(simp) = simplify_type(self.tcx, ty, TreatParams::InstantiateWithInfer) {
             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

@@ -714,7 +714,7 @@ 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::AsCandidateKey) else {
+        let Some(simp) = simplify_type(self.tcx, self_ty, TreatParams::InstantiateWithInfer) else {
             bug!("unexpected incoherent type: {:?}", self_ty)
         };
         for &impl_def_id in self.tcx.incoherent_impls(simp).into_iter().flatten() {

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -2234,8 +2234,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let target_ty = self
                 .autoderef(sugg_span, rcvr_ty)
                 .find(|(rcvr_ty, _)| {
-                    DeepRejectCtxt::new(self.tcx, TreatParams::ForLookup)
-                        .types_may_unify(*rcvr_ty, impl_ty)
+                    DeepRejectCtxt::relate_rigid_infer(self.tcx).types_may_unify(*rcvr_ty, impl_ty)
                 })
                 .map_or(impl_ty, |(ty, _)| ty)
                 .peel_refs();
@@ -2497,7 +2496,7 @@ 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::AsCandidateKey)
+            simplify_type(tcx, ty, TreatParams::InstantiateWithInfer)
                 .and_then(|simp| {
                     tcx.incoherent_impls(simp)
                         .into_iter()
@@ -3962,7 +3961,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // cases where a positive bound implies a negative impl.
                 (candidates, Vec::new())
             } else if let Some(simp_rcvr_ty) =
-                simplify_type(self.tcx, rcvr_ty, TreatParams::ForLookup)
+                simplify_type(self.tcx, rcvr_ty, TreatParams::AsRigid)
             {
                 let mut potential_candidates = Vec::new();
                 let mut explicitly_negative = Vec::new();
@@ -3980,7 +3979,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         .any(|header| {
                             let imp = header.trait_ref.instantiate_identity();
                             let imp_simp =
-                                simplify_type(self.tcx, imp.self_ty(), TreatParams::ForLookup);
+                                simplify_type(self.tcx, imp.self_ty(), TreatParams::AsRigid);
                             imp_simp.is_some_and(|s| s == simp_rcvr_ty)
                         })
                     {

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -2017,7 +2017,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 let simplified_self_ty = fast_reject::simplify_type(
                     self.tcx,
                     trait_ref.self_ty(),
-                    TreatParams::AsCandidateKey,
+                    TreatParams::InstantiateWithInfer,
                 );
                 trait_impls
                     .entry(trait_ref.def_id)

compiler/rustc_middle/src/ty/context.rs

@@ -428,7 +428,7 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
                 let simp = ty::fast_reject::simplify_type(
                     tcx,
                     self_ty,
-                    ty::fast_reject::TreatParams::ForLookup,
+                    ty::fast_reject::TreatParams::AsRigid,
                 )
                 .unwrap();
                 consider_impls_for_simplified_type(simp);

compiler/rustc_middle/src/ty/fast_reject.rs

@@ -3,6 +3,14 @@ pub use rustc_type_ir::fast_reject::*;
 
 use super::TyCtxt;
 
-pub type DeepRejectCtxt<'tcx> = rustc_type_ir::fast_reject::DeepRejectCtxt<TyCtxt<'tcx>>;
+pub type DeepRejectCtxt<
+    'tcx,
+    const INSTANTIATE_LHS_WITH_INFER: bool,
+    const INSTANTIATE_RHS_WITH_INFER: bool,
+> = rustc_type_ir::fast_reject::DeepRejectCtxt<
+    TyCtxt<'tcx>,
+    INSTANTIATE_LHS_WITH_INFER,
+    INSTANTIATE_RHS_WITH_INFER,
+>;
 
 pub type SimplifiedType = rustc_type_ir::fast_reject::SimplifiedType<DefId>;

compiler/rustc_middle/src/ty/trait_def.rs

@@ -168,9 +168,9 @@ impl<'tcx> TyCtxt<'tcx> {
         // whose outer level is not a parameter or projection. Especially for things like
         // `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.
-        // Note that we're using `TreatParams::ForLookup` to query `non_blanket_impls` while using
-        // `TreatParams::AsCandidateKey` while actually adding them.
-        if let Some(simp) = fast_reject::simplify_type(self, self_ty, TreatParams::ForLookup) {
+        // Note that we're using `TreatParams::AsRigid` to query `non_blanket_impls` while using
+        // `TreatParams::InstantiateWithInfer` while actually adding them.
+        if let Some(simp) = fast_reject::simplify_type(self, self_ty, TreatParams::AsRigid) {
             if let Some(impls) = impls.non_blanket_impls.get(&simp) {
                 for &impl_def_id in impls {
                     f(impl_def_id);
@@ -190,7 +190,9 @@ impl<'tcx> TyCtxt<'tcx> {
         self_ty: Ty<'tcx>,
     ) -> impl Iterator<Item = DefId> + 'tcx {
         let impls = self.trait_impls_of(trait_def_id);
-        if let Some(simp) = fast_reject::simplify_type(self, self_ty, TreatParams::AsCandidateKey) {
+        if let Some(simp) =
+            fast_reject::simplify_type(self, self_ty, TreatParams::InstantiateWithInfer)
+        {
             if let Some(impls) = impls.non_blanket_impls.get(&simp) {
                 return impls.iter().copied();
             }
@@ -239,7 +241,7 @@ pub(super) fn trait_impls_of_provider(tcx: TyCtxt<'_>, trait_id: DefId) -> Trait
         let impl_self_ty = tcx.type_of(impl_def_id).instantiate_identity();
 
         if let Some(simplified_self_ty) =
-            fast_reject::simplify_type(tcx, impl_self_ty, TreatParams::AsCandidateKey)
+            fast_reject::simplify_type(tcx, impl_self_ty, TreatParams::InstantiateWithInfer)
         {
             impls.non_blanket_impls.entry(simplified_self_ty).or_default().push(impl_def_id);
         } else {

compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs

@@ -3,7 +3,7 @@ mod inherent;
 mod opaque_types;
 mod weak_types;
 
-use rustc_type_ir::fast_reject::{DeepRejectCtxt, TreatParams};
+use rustc_type_ir::fast_reject::DeepRejectCtxt;
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::lang_items::TraitSolverLangItem;
 use rustc_type_ir::{self as ty, Interner, NormalizesTo, Upcast as _};
@@ -106,6 +106,12 @@ where
         if let Some(projection_pred) = assumption.as_projection_clause() {
             if projection_pred.projection_def_id() == goal.predicate.def_id() {
                 let cx = ecx.cx();
+                if !DeepRejectCtxt::relate_rigid_rigid(ecx.cx()).args_may_unify(
+                    goal.predicate.alias.args,
+                    projection_pred.skip_binder().projection_term.args,
+                ) {
+                    return Err(NoSolution);
+                }
                 ecx.probe_trait_candidate(source).enter(|ecx| {
                     let assumption_projection_pred =
                         ecx.instantiate_binder_with_infer(projection_pred);
@@ -144,7 +150,7 @@ where
 
         let goal_trait_ref = goal.predicate.alias.trait_ref(cx);
         let impl_trait_ref = cx.impl_trait_ref(impl_def_id);
-        if !DeepRejectCtxt::new(ecx.cx(), TreatParams::ForLookup).args_may_unify(
+        if !DeepRejectCtxt::relate_rigid_infer(ecx.cx()).args_may_unify(
             goal.predicate.alias.trait_ref(cx).args,
             impl_trait_ref.skip_binder().args,
         ) {

compiler/rustc_next_trait_solver/src/solve/trait_goals.rs

@@ -2,7 +2,7 @@
 
 use rustc_ast_ir::Movability;
 use rustc_type_ir::data_structures::IndexSet;
-use rustc_type_ir::fast_reject::{DeepRejectCtxt, TreatParams};
+use rustc_type_ir::fast_reject::DeepRejectCtxt;
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::lang_items::TraitSolverLangItem;
 use rustc_type_ir::visit::TypeVisitableExt as _;
@@ -47,7 +47,7 @@ where
         let cx = ecx.cx();
 
         let impl_trait_ref = cx.impl_trait_ref(impl_def_id);
-        if !DeepRejectCtxt::new(ecx.cx(), TreatParams::ForLookup)
+        if !DeepRejectCtxt::relate_rigid_infer(ecx.cx())
             .args_may_unify(goal.predicate.trait_ref.args, impl_trait_ref.skip_binder().args)
         {
             return Err(NoSolution);
@@ -124,6 +124,13 @@ where
             if trait_clause.def_id() == goal.predicate.def_id()
                 && trait_clause.polarity() == goal.predicate.polarity
             {
+                if !DeepRejectCtxt::relate_rigid_rigid(ecx.cx()).args_may_unify(
+                    goal.predicate.trait_ref.args,
+                    trait_clause.skip_binder().trait_ref.args,
+                ) {
+                    return Err(NoSolution);
+                }
+
                 ecx.probe_trait_candidate(source).enter(|ecx| {
                     let assumption_trait_pred = ecx.instantiate_binder_with_infer(trait_clause);
                     ecx.eq(

compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs

@@ -4,7 +4,7 @@ use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_middle::traits::{ObligationCause, ObligationCauseCode};
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
-use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
+use rustc_middle::ty::fast_reject::DeepRejectCtxt;
 use rustc_middle::ty::print::{FmtPrinter, Printer};
 use rustc_middle::ty::{self, suggest_constraining_type_param, Ty};
 use rustc_span::def_id::DefId;
@@ -316,7 +316,7 @@ impl<T> Trait<T> for X {
                     {
                         let mut has_matching_impl = false;
                         tcx.for_each_relevant_impl(def_id, values.found, |did| {
-                            if DeepRejectCtxt::new(tcx, TreatParams::ForLookup)
+                            if DeepRejectCtxt::relate_rigid_infer(tcx)
                                 .types_may_unify(values.found, tcx.type_of(did).skip_binder())
                             {
                                 has_matching_impl = true;
@@ -337,7 +337,7 @@ impl<T> Trait<T> for X {
                     {
                         let mut has_matching_impl = false;
                         tcx.for_each_relevant_impl(def_id, values.expected, |did| {
-                            if DeepRejectCtxt::new(tcx, TreatParams::ForLookup)
+                            if DeepRejectCtxt::relate_rigid_infer(tcx)
                                 .types_may_unify(values.expected, tcx.type_of(did).skip_binder())
                             {
                                 has_matching_impl = true;
@@ -357,7 +357,7 @@ impl<T> Trait<T> for X {
                     {
                         let mut has_matching_impl = false;
                         tcx.for_each_relevant_impl(def_id, values.found, |did| {
-                            if DeepRejectCtxt::new(tcx, TreatParams::ForLookup)
+                            if DeepRejectCtxt::relate_rigid_infer(tcx)
                                 .types_may_unify(values.found, tcx.type_of(did).skip_binder())
                             {
                                 has_matching_impl = true;

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -15,7 +15,7 @@ use rustc_middle::bug;
 use rustc_middle::traits::query::NoSolution;
 use rustc_middle::traits::solve::{CandidateSource, Certainty, Goal};
 use rustc_middle::traits::specialization_graph::OverlapMode;
-use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
+use rustc_middle::ty::fast_reject::DeepRejectCtxt;
 use rustc_middle::ty::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor};
 use rustc_middle::ty::{self, Ty, TyCtxt};
 pub use rustc_next_trait_solver::coherence::*;
@@ -94,7 +94,7 @@ 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::new(tcx, TreatParams::AsCandidateKey);
+    let drcx = DeepRejectCtxt::relate_infer_infer(tcx);
     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/project.rs

@@ -13,6 +13,7 @@ use rustc_infer::traits::ObligationCauseCode;
 use rustc_middle::traits::select::OverflowError;
 pub use rustc_middle::traits::Reveal;
 use rustc_middle::traits::{BuiltinImplSource, ImplSource, ImplSourceUserDefinedData};
+use rustc_middle::ty::fast_reject::DeepRejectCtxt;
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::visit::{MaxUniverse, TypeVisitable, TypeVisitableExt};
 use rustc_middle::ty::{self, Term, Ty, TyCtxt, Upcast};
@@ -885,6 +886,7 @@ fn assemble_candidates_from_predicates<'cx, 'tcx>(
     potentially_unnormalized_candidates: bool,
 ) {
     let infcx = selcx.infcx;
+    let drcx = DeepRejectCtxt::relate_rigid_rigid(selcx.tcx());
     for predicate in env_predicates {
         let bound_predicate = predicate.kind();
         if let ty::ClauseKind::Projection(data) = predicate.kind().skip_binder() {
@@ -893,6 +895,12 @@ fn assemble_candidates_from_predicates<'cx, 'tcx>(
                 continue;
             }
 
+            if !drcx
+                .args_may_unify(obligation.predicate.args, data.skip_binder().projection_term.args)
+            {
+                continue;
+            }
+
             let is_match = infcx.probe(|_| {
                 selcx.match_projection_projections(
                     obligation,

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

@@ -13,7 +13,7 @@ use hir::LangItem;
 use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
 use rustc_hir as hir;
 use rustc_infer::traits::{Obligation, ObligationCause, PolyTraitObligation, SelectionError};
-use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
+use rustc_middle::ty::fast_reject::DeepRejectCtxt;
 use rustc_middle::ty::{self, ToPolyTraitRef, Ty, TypeVisitableExt};
 use rustc_middle::{bug, span_bug};
 
@@ -247,11 +247,17 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             .filter(|p| p.def_id() == stack.obligation.predicate.def_id())
             .filter(|p| p.polarity() == stack.obligation.predicate.polarity());
 
+        let drcx = DeepRejectCtxt::relate_rigid_rigid(self.tcx());
+        let obligation_args = stack.obligation.predicate.skip_binder().trait_ref.args;
         // Keep only those bounds which may apply, and propagate overflow if it occurs.
         for bound in bounds {
+            let bound_trait_ref = bound.map_bound(|t| t.trait_ref);
+            if !drcx.args_may_unify(obligation_args, bound_trait_ref.skip_binder().args) {
+                continue;
+            }
             // FIXME(oli-obk): it is suspicious that we are dropping the constness and
             // polarity here.
-            let wc = self.where_clause_may_apply(stack, bound.map_bound(|t| t.trait_ref))?;
+            let wc = self.where_clause_may_apply(stack, bound_trait_ref)?;
             if wc.may_apply() {
                 candidates.vec.push(ParamCandidate(bound));
             }
@@ -580,7 +586,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             return;
         }
 
-        let drcx = DeepRejectCtxt::new(self.tcx(), TreatParams::ForLookup);
+        let drcx = DeepRejectCtxt::relate_rigid_infer(self.tcx());
         let obligation_args = obligation.predicate.skip_binder().trait_ref.args;
         self.tcx().for_each_relevant_impl(
             obligation.predicate.def_id(),

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

@@ -40,7 +40,7 @@ impl<'tcx> Children {
     fn insert_blindly(&mut self, tcx: TyCtxt<'tcx>, impl_def_id: DefId) {
         let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap().skip_binder();
         if let Some(st) =
-            fast_reject::simplify_type(tcx, trait_ref.self_ty(), TreatParams::AsCandidateKey)
+            fast_reject::simplify_type(tcx, trait_ref.self_ty(), TreatParams::InstantiateWithInfer)
         {
             debug!("insert_blindly: impl_def_id={:?} st={:?}", impl_def_id, st);
             self.non_blanket_impls.entry(st).or_default().push(impl_def_id)
@@ -57,7 +57,7 @@ impl<'tcx> Children {
         let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap().skip_binder();
         let vec: &mut Vec<DefId>;
         if let Some(st) =
-            fast_reject::simplify_type(tcx, trait_ref.self_ty(), TreatParams::AsCandidateKey)
+            fast_reject::simplify_type(tcx, trait_ref.self_ty(), TreatParams::InstantiateWithInfer)
         {
             debug!("remove_existing: impl_def_id={:?} st={:?}", impl_def_id, st);
             vec = self.non_blanket_impls.get_mut(&st).unwrap();
@@ -278,7 +278,7 @@ impl<'tcx> Graph {
         let mut parent = trait_def_id;
         let mut last_lint = None;
         let simplified =
-            fast_reject::simplify_type(tcx, trait_ref.self_ty(), TreatParams::AsCandidateKey);
+            fast_reject::simplify_type(tcx, trait_ref.self_ty(), TreatParams::InstantiateWithInfer);
 
         // Descend the specialization tree, where `parent` is the current parent node.
         loop {