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

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)
         })
     }
 }