Remove unnecessary param-env from lexical region resolution and fully structural relations

compiler/rustc_borrowck/src/region_infer/mod.rs

@@ -674,13 +674,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         // eagerly.
         let mut outlives_requirements = infcx.tcx.is_typeck_child(mir_def_id).then(Vec::new);
 
-        self.check_type_tests(
-            infcx,
-            param_env,
-            body,
-            outlives_requirements.as_mut(),
-            &mut errors_buffer,
-        );
+        self.check_type_tests(infcx, body, outlives_requirements.as_mut(), &mut errors_buffer);
 
         debug!(?errors_buffer);
         debug!(?outlives_requirements);
@@ -938,7 +932,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     fn check_type_tests(
         &self,
         infcx: &InferCtxt<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
         body: &Body<'tcx>,
         mut propagated_outlives_requirements: Option<&mut Vec<ClosureOutlivesRequirement<'tcx>>>,
         errors_buffer: &mut RegionErrors<'tcx>,
@@ -956,7 +949,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             let generic_ty = type_test.generic_kind.to_ty(tcx);
             if self.eval_verify_bound(
                 infcx,
-                param_env,
                 generic_ty,
                 type_test.lower_bound,
                 &type_test.verify_bound,
@@ -967,7 +959,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             if let Some(propagated_outlives_requirements) = &mut propagated_outlives_requirements {
                 if self.try_promote_type_test(
                     infcx,
-                    param_env,
                     body,
                     type_test,
                     propagated_outlives_requirements,
@@ -1025,7 +1016,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     fn try_promote_type_test(
         &self,
         infcx: &InferCtxt<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
         body: &Body<'tcx>,
         type_test: &TypeTest<'tcx>,
         propagated_outlives_requirements: &mut Vec<ClosureOutlivesRequirement<'tcx>>,
@@ -1087,7 +1077,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             // where `ur` is a local bound -- we are sometimes in a
             // position to prove things that our caller cannot. See
             // #53570 for an example.
-            if self.eval_verify_bound(infcx, param_env, generic_ty, ur, &type_test.verify_bound) {
+            if self.eval_verify_bound(infcx, generic_ty, ur, &type_test.verify_bound) {
                 continue;
             }
 
@@ -1270,7 +1260,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     fn eval_verify_bound(
         &self,
         infcx: &InferCtxt<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
         generic_ty: Ty<'tcx>,
         lower_bound: RegionVid,
         verify_bound: &VerifyBound<'tcx>,
@@ -1279,7 +1268,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
 
         match verify_bound {
             VerifyBound::IfEq(verify_if_eq_b) => {
-                self.eval_if_eq(infcx, param_env, generic_ty, lower_bound, *verify_if_eq_b)
+                self.eval_if_eq(infcx, generic_ty, lower_bound, *verify_if_eq_b)
             }
 
             VerifyBound::IsEmpty => {
@@ -1293,11 +1282,11 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             }
 
             VerifyBound::AnyBound(verify_bounds) => verify_bounds.iter().any(|verify_bound| {
-                self.eval_verify_bound(infcx, param_env, generic_ty, lower_bound, verify_bound)
+                self.eval_verify_bound(infcx, generic_ty, lower_bound, verify_bound)
             }),
 
             VerifyBound::AllBounds(verify_bounds) => verify_bounds.iter().all(|verify_bound| {
-                self.eval_verify_bound(infcx, param_env, generic_ty, lower_bound, verify_bound)
+                self.eval_verify_bound(infcx, generic_ty, lower_bound, verify_bound)
             }),
         }
     }
@@ -1305,19 +1294,13 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     fn eval_if_eq(
         &self,
         infcx: &InferCtxt<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
         generic_ty: Ty<'tcx>,
         lower_bound: RegionVid,
         verify_if_eq_b: ty::Binder<'tcx, VerifyIfEq<'tcx>>,
     ) -> bool {
         let generic_ty = self.normalize_to_scc_representatives(infcx.tcx, generic_ty);
         let verify_if_eq_b = self.normalize_to_scc_representatives(infcx.tcx, verify_if_eq_b);
-        match test_type_match::extract_verify_if_eq(
-            infcx.tcx,
-            param_env,
-            &verify_if_eq_b,
-            generic_ty,
-        ) {
+        match test_type_match::extract_verify_if_eq(infcx.tcx, &verify_if_eq_b, generic_ty) {
             Some(r) => {
                 let r_vid = self.to_region_vid(r);
                 self.eval_outlives(r_vid, lower_bound)

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -2654,8 +2654,7 @@ impl<'tcx> TypeRelation<'tcx> for SameTypeModuloInfer<'_, 'tcx> {
     }
 
     fn param_env(&self) -> ty::ParamEnv<'tcx> {
-        // Unused, only for consts which we treat as always equal
-        ty::ParamEnv::empty()
+        unreachable!("purely structural relation should not need a param-env")
     }
 
     fn tag(&self) -> &'static str {

compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs

@@ -31,13 +31,12 @@ use super::outlives::test_type_match;
 /// all the variables as well as a set of errors that must be reported.
 #[instrument(level = "debug", skip(region_rels, var_infos, data))]
 pub(crate) fn resolve<'tcx>(
-    param_env: ty::ParamEnv<'tcx>,
     region_rels: &RegionRelations<'_, 'tcx>,
     var_infos: VarInfos,
     data: RegionConstraintData<'tcx>,
 ) -> (LexicalRegionResolutions<'tcx>, Vec<RegionResolutionError<'tcx>>) {
     let mut errors = vec![];
-    let mut resolver = LexicalResolver { param_env, region_rels, var_infos, data };
+    let mut resolver = LexicalResolver { region_rels, var_infos, data };
     let values = resolver.infer_variable_values(&mut errors);
     (values, errors)
 }
@@ -120,7 +119,6 @@ struct RegionAndOrigin<'tcx> {
 type RegionGraph<'tcx> = Graph<(), Constraint<'tcx>>;
 
 struct LexicalResolver<'cx, 'tcx> {
-    param_env: ty::ParamEnv<'tcx>,
     region_rels: &'cx RegionRelations<'cx, 'tcx>,
     var_infos: VarInfos,
     data: RegionConstraintData<'tcx>,
@@ -914,12 +912,8 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
         match bound {
             VerifyBound::IfEq(verify_if_eq_b) => {
                 let verify_if_eq_b = var_values.normalize(self.region_rels.tcx, *verify_if_eq_b);
-                match test_type_match::extract_verify_if_eq(
-                    self.tcx(),
-                    self.param_env,
-                    &verify_if_eq_b,
-                    generic_ty,
-                ) {
+                match test_type_match::extract_verify_if_eq(self.tcx(), &verify_if_eq_b, generic_ty)
+                {
                     Some(r) => {
                         self.bound_is_met(&VerifyBound::OutlivedBy(r), var_values, generic_ty, min)
                     }

compiler/rustc_infer/src/infer/outlives/for_liveness.rs

@@ -84,7 +84,6 @@ where
                         } else {
                             test_type_match::extract_verify_if_eq(
                                 tcx,
-                                param_env,
                                 &outlives.map_bound(|ty::OutlivesPredicate(ty, bound)| {
                                     VerifyIfEq { ty, bound }
                                 }),

compiler/rustc_infer/src/infer/outlives/mod.rs

@@ -67,7 +67,7 @@ impl<'tcx> InferCtxt<'tcx> {
         let region_rels = &RegionRelations::new(self.tcx, outlives_env.free_region_map());
 
         let (lexical_region_resolutions, errors) =
-            lexical_region_resolve::resolve(outlives_env.param_env, region_rels, var_infos, data);
+            lexical_region_resolve::resolve(region_rels, var_infos, data);
 
         let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions));
         assert!(old_value.is_none());

compiler/rustc_infer/src/infer/outlives/test_type_match.rs

@@ -36,15 +36,14 @@ use crate::infer::region_constraints::VerifyIfEq;
 /// like are used. This is a particular challenge since this function is invoked
 /// very late in inference and hence cannot make use of the normal inference
 /// machinery.
-#[instrument(level = "debug", skip(tcx, param_env))]
+#[instrument(level = "debug", skip(tcx))]
 pub fn extract_verify_if_eq<'tcx>(
     tcx: TyCtxt<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
     verify_if_eq_b: &ty::Binder<'tcx, VerifyIfEq<'tcx>>,
     test_ty: Ty<'tcx>,
 ) -> Option<ty::Region<'tcx>> {
     assert!(!verify_if_eq_b.has_escaping_bound_vars());
-    let mut m = MatchAgainstHigherRankedOutlives::new(tcx, param_env);
+    let mut m = MatchAgainstHigherRankedOutlives::new(tcx);
     let verify_if_eq = verify_if_eq_b.skip_binder();
     m.relate(verify_if_eq.ty, test_ty).ok()?;
 
@@ -73,10 +72,9 @@ pub fn extract_verify_if_eq<'tcx>(
 }
 
 /// True if a (potentially higher-ranked) outlives
-#[instrument(level = "debug", skip(tcx, param_env))]
+#[instrument(level = "debug", skip(tcx))]
 pub(super) fn can_match_erased_ty<'tcx>(
     tcx: TyCtxt<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
     outlives_predicate: ty::Binder<'tcx, ty::TypeOutlivesPredicate<'tcx>>,
     erased_ty: Ty<'tcx>,
 ) -> bool {
@@ -87,25 +85,20 @@ pub(super) fn can_match_erased_ty<'tcx>(
         // pointless micro-optimization
         true
     } else {
-        MatchAgainstHigherRankedOutlives::new(tcx, param_env).relate(outlives_ty, erased_ty).is_ok()
+        MatchAgainstHigherRankedOutlives::new(tcx).relate(outlives_ty, erased_ty).is_ok()
     }
 }
 
 struct MatchAgainstHigherRankedOutlives<'tcx> {
     tcx: TyCtxt<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
     pattern_depth: ty::DebruijnIndex,
     map: FxHashMap<ty::BoundRegion, ty::Region<'tcx>>,
 }
 
 impl<'tcx> MatchAgainstHigherRankedOutlives<'tcx> {
-    fn new(
-        tcx: TyCtxt<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
-    ) -> MatchAgainstHigherRankedOutlives<'tcx> {
+    fn new(tcx: TyCtxt<'tcx>) -> MatchAgainstHigherRankedOutlives<'tcx> {
         MatchAgainstHigherRankedOutlives {
             tcx,
-            param_env,
             pattern_depth: ty::INNERMOST,
             map: FxHashMap::default(),
         }
@@ -144,15 +137,17 @@ impl<'tcx> MatchAgainstHigherRankedOutlives<'tcx> {
 
 impl<'tcx> TypeRelation<'tcx> for MatchAgainstHigherRankedOutlives<'tcx> {
     fn tag(&self) -> &'static str {
-        "Match"
+        "MatchAgainstHigherRankedOutlives"
     }
 
     fn tcx(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
+
     fn param_env(&self) -> ty::ParamEnv<'tcx> {
-        self.param_env
+        unreachable!("purely structural relation should not need a param-env")
     }
+
     fn a_is_expected(&self) -> bool {
         true
     } // irrelevant

compiler/rustc_infer/src/infer/outlives/verify.rs

@@ -312,14 +312,8 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
     ) -> impl Iterator<Item = ty::Binder<'tcx, ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>>>
     {
         let tcx = self.tcx;
-        let param_env = self.param_env;
         clauses.filter_map(|p| p.as_type_outlives_clause()).filter(move |outlives_predicate| {
-            super::test_type_match::can_match_erased_ty(
-                tcx,
-                param_env,
-                *outlives_predicate,
-                erased_ty,
-            )
+            super::test_type_match::can_match_erased_ty(tcx, *outlives_predicate, erased_ty)
         })
     }
 }

compiler/rustc_middle/src/ty/_match.rs

@@ -20,12 +20,11 @@ use crate::ty::{self, InferConst, Ty, TyCtxt};
 /// affects any type variables or unification state.
 pub struct MatchAgainstFreshVars<'tcx> {
     tcx: TyCtxt<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
 }
 
 impl<'tcx> MatchAgainstFreshVars<'tcx> {
-    pub fn new(tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> MatchAgainstFreshVars<'tcx> {
-        MatchAgainstFreshVars { tcx, param_env }
+    pub fn new(tcx: TyCtxt<'tcx>) -> MatchAgainstFreshVars<'tcx> {
+        MatchAgainstFreshVars { tcx }
     }
 }
 
@@ -33,13 +32,15 @@ impl<'tcx> TypeRelation<'tcx> for MatchAgainstFreshVars<'tcx> {
     fn tag(&self) -> &'static str {
         "MatchAgainstFreshVars"
     }
+
     fn tcx(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
 
     fn param_env(&self) -> ty::ParamEnv<'tcx> {
-        self.param_env
+        panic!("relation should not need a param-env")
     }
+
     fn a_is_expected(&self) -> bool {
         true
     } // irrelevant

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

@@ -1226,11 +1226,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         if unbound_input_types
             && stack.iter().skip(1).any(|prev| {
                 stack.obligation.param_env == prev.obligation.param_env
-                    && self.match_fresh_trait_refs(
-                        stack.fresh_trait_pred,
-                        prev.fresh_trait_pred,
-                        prev.obligation.param_env,
-                    )
+                    && self.match_fresh_trait_refs(stack.fresh_trait_pred, prev.fresh_trait_pred)
             })
         {
             debug!("evaluate_stack --> unbound argument, recursive --> giving up",);
@@ -2632,9 +2628,8 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         &self,
         previous: ty::PolyTraitPredicate<'tcx>,
         current: ty::PolyTraitPredicate<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
     ) -> bool {
-        let mut matcher = MatchAgainstFreshVars::new(self.tcx(), param_env);
+        let mut matcher = MatchAgainstFreshVars::new(self.tcx());
         matcher.relate(previous, current).is_ok()
     }