Auto merge of rust-lang#119101 - compiler-errors:outlives, r=<try>

Normalize region obligation in lexical region resolution with next-gen solver

Draft because this is not yet done -- no tests or anything... but this is the general approach I've found to work.

r? `@ghost`

Author: bors

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 => {
@@ -1293,31 +1282,25 @@ 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)
             }),
         }
     }
 
     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_borrowck/src/type_check/free_region_relations.rs

@@ -199,7 +199,8 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
 
         // Insert the facts we know from the predicates. Why? Why not.
         let param_env = self.param_env;
-        self.add_outlives_bounds(outlives::explicit_outlives_bounds(param_env));
+        // FIXME(-Znext-solver): This param-env is not normalized!
+        self.add_outlives_bounds(outlives::explicit_outlives_bounds(param_env.caller_bounds()));
 
         // - outlives is reflexive, so `'r: 'r` for every region `'r`
         // - `'static: 'r` for every region `'r`

compiler/rustc_hir_analysis/src/check/check.rs

@@ -10,6 +10,7 @@ use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, DefKind};
 use rustc_hir::def_id::LocalModDefId;
 use rustc_hir::Node;
+use rustc_infer::infer::outlives::env::RegionCheckingAssumptions;
 use rustc_infer::infer::{RegionVariableOrigin, TyCtxtInferExt};
 use rustc_infer::traits::{Obligation, TraitEngineExt as _};
 use rustc_lint_defs::builtin::REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS;
@@ -353,8 +354,8 @@ fn check_opaque_meets_bounds<'tcx>(
         hir::OpaqueTyOrigin::TyAlias { .. } => {
             let wf_tys = ocx.assumed_wf_types_and_report_errors(param_env, def_id)?;
             let implied_bounds = infcx.implied_bounds_tys(param_env, def_id, wf_tys);
-            let outlives_env = OutlivesEnvironment::with_bounds(param_env, implied_bounds);
-            ocx.resolve_regions_and_report_errors(defining_use_anchor, &outlives_env)?;
+            let assumptions = RegionCheckingAssumptions::with_bounds(param_env, implied_bounds);
+            ocx.resolve_regions_and_report_errors(defining_use_anchor, &assumptions)?;
         }
     }
     // Check that any hidden types found during wf checking match the hidden types that `type_of` sees.

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -7,7 +7,7 @@ use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::intravisit;
 use rustc_hir::{GenericParamKind, ImplItemKind};
-use rustc_infer::infer::outlives::env::OutlivesEnvironment;
+use rustc_infer::infer::outlives::env::RegionCheckingAssumptions;
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc_infer::infer::{self, InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::util;
@@ -20,6 +20,7 @@ use rustc_middle::ty::{
 };
 use rustc_middle::ty::{GenericParamDefKind, TyCtxt};
 use rustc_span::{Span, DUMMY_SP};
+use rustc_trait_selection::regions::InferCtxtRegionExt;
 use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt;
 use rustc_trait_selection::traits::outlives_bounds::InferCtxtExt as _;
 use rustc_trait_selection::traits::{
@@ -376,11 +377,11 @@ fn compare_method_predicate_entailment<'tcx>(
 
     // Finally, resolve all regions. This catches wily misuses of
     // lifetime parameters.
-    let outlives_env = OutlivesEnvironment::with_bounds(
+    let assumptions = RegionCheckingAssumptions::with_bounds(
         param_env,
         infcx.implied_bounds_tys(param_env, impl_m_def_id, wf_tys),
     );
-    let errors = infcx.resolve_regions(&outlives_env);
+    let errors = infcx.resolve_regions_normalizing_outlives_obligations(&assumptions);
     if !errors.is_empty() {
         return Err(infcx
             .tainted_by_errors()
@@ -700,11 +701,11 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
 
     // Finally, resolve all regions. This catches wily misuses of
     // lifetime parameters.
-    let outlives_env = OutlivesEnvironment::with_bounds(
+    let assumptions = RegionCheckingAssumptions::with_bounds(
         param_env,
         infcx.implied_bounds_tys(param_env, impl_m_def_id, wf_tys),
     );
-    ocx.resolve_regions_and_report_errors(impl_m_def_id, &outlives_env)?;
+    ocx.resolve_regions_and_report_errors(impl_m_def_id, &assumptions)?;
 
     let mut remapped_types = FxHashMap::default();
     for (def_id, (ty, args)) in collected_types {
@@ -1872,8 +1873,8 @@ fn compare_const_predicate_entailment<'tcx>(
         return Err(infcx.err_ctxt().report_fulfillment_errors(errors));
     }
 
-    let outlives_env = OutlivesEnvironment::new(param_env);
-    ocx.resolve_regions_and_report_errors(impl_ct_def_id, &outlives_env)
+    let assumptions = RegionCheckingAssumptions::new(param_env);
+    ocx.resolve_regions_and_report_errors(impl_ct_def_id, &assumptions)
 }
 
 pub(super) fn compare_impl_ty<'tcx>(
@@ -1968,8 +1969,8 @@ fn compare_type_predicate_entailment<'tcx>(
 
     // Finally, resolve all regions. This catches wily misuses of
     // lifetime parameters.
-    let outlives_env = OutlivesEnvironment::new(param_env);
-    ocx.resolve_regions_and_report_errors(impl_ty_def_id, &outlives_env)
+    let assumptions = RegionCheckingAssumptions::new(param_env);
+    ocx.resolve_regions_and_report_errors(impl_ty_def_id, &assumptions)
 }
 
 /// Validate that `ProjectionCandidate`s created for this associated type will
@@ -2074,8 +2075,8 @@ pub(super) fn check_type_bounds<'tcx>(
     // Finally, resolve all regions. This catches wily misuses of
     // lifetime parameters.
     let implied_bounds = infcx.implied_bounds_tys(param_env, impl_ty_def_id, assumed_wf_types);
-    let outlives_env = OutlivesEnvironment::with_bounds(param_env, implied_bounds);
-    ocx.resolve_regions_and_report_errors(impl_ty_def_id, &outlives_env)
+    let assumptions = RegionCheckingAssumptions::with_bounds(param_env, implied_bounds);
+    ocx.resolve_regions_and_report_errors(impl_ty_def_id, &assumptions)
 }
 
 /// Install projection predicates that allow GATs to project to their own

compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs

@@ -1,13 +1,15 @@
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
-use rustc_infer::infer::{outlives::env::OutlivesEnvironment, TyCtxtInferExt};
+use rustc_infer::infer::outlives::env::RegionCheckingAssumptions;
+use rustc_infer::infer::TyCtxtInferExt;
 use rustc_lint_defs::builtin::REFINING_IMPL_TRAIT;
 use rustc_middle::traits::{ObligationCause, Reveal};
 use rustc_middle::ty::{
     self, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperVisitable, TypeVisitable, TypeVisitor,
 };
 use rustc_span::{Span, DUMMY_SP};
+use rustc_trait_selection::regions::InferCtxtRegionExt;
 use rustc_trait_selection::traits::{
     elaborate, normalize_param_env_or_error, outlives_bounds::InferCtxtExt, ObligationCtxt,
 };
@@ -159,11 +161,11 @@ pub(super) fn check_refining_return_position_impl_trait_in_trait<'tcx>(
         );
         return;
     }
-    let outlives_env = OutlivesEnvironment::with_bounds(
+    let assumptions = RegionCheckingAssumptions::with_bounds(
         param_env,
         infcx.implied_bounds_tys(param_env, impl_m.def_id.expect_local(), implied_wf_types),
     );
-    let errors = infcx.resolve_regions(&outlives_env);
+    let errors = infcx.resolve_regions_normalizing_outlives_obligations(&assumptions);
     if !errors.is_empty() {
         tcx.sess.span_delayed_bug(
             DUMMY_SP,

compiler/rustc_hir_analysis/src/check/dropck.rs

@@ -3,11 +3,12 @@
 // We don't do any drop checking during hir typeck.
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{struct_span_err, ErrorGuaranteed};
-use rustc_infer::infer::outlives::env::OutlivesEnvironment;
+use rustc_infer::infer::outlives::env::RegionCheckingAssumptions;
 use rustc_infer::infer::{RegionResolutionError, TyCtxtInferExt};
 use rustc_middle::ty::util::CheckRegions;
 use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, TyCtxt};
+use rustc_trait_selection::regions::InferCtxtRegionExt;
 use rustc_trait_selection::traits::{self, ObligationCtxt};
 
 use crate::errors;
@@ -169,7 +170,9 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
         return Err(guar.unwrap());
     }
 
-    let errors = ocx.infcx.resolve_regions(&OutlivesEnvironment::new(param_env));
+    let errors = ocx.infcx.resolve_regions_normalizing_outlives_obligations(
+        &RegionCheckingAssumptions::new(param_env),
+    );
     if !errors.is_empty() {
         let mut guar = None;
         for error in errors {
@@ -184,6 +187,7 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
                 RegionResolutionError::UpperBoundUniverseConflict(a, _, _, _, b) => {
                     format!("{b}: {a}", a = ty::Region::new_var(tcx, a))
                 }
+                RegionResolutionError::CannotNormalize(..) => todo!(),
             };
             guar = Some(
                 struct_span_err!(

compiler/rustc_hir_analysis/src/check/mod.rs

@@ -83,7 +83,7 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::Visitor;
 use rustc_index::bit_set::BitSet;
 use rustc_infer::infer::error_reporting::ObligationCauseExt as _;
-use rustc_infer::infer::outlives::env::OutlivesEnvironment;
+use rustc_infer::infer::outlives::env::RegionCheckingAssumptions;
 use rustc_infer::infer::{self, TyCtxtInferExt as _};
 use rustc_infer::traits::ObligationCause;
 use rustc_middle::query::Providers;
@@ -633,8 +633,8 @@ pub fn check_function_signature<'tcx>(
         }
     }
 
-    let outlives_env = OutlivesEnvironment::new(param_env);
-    if let Err(e) = ocx.resolve_regions_and_report_errors(local_id, &outlives_env) {
+    let assumptions = RegionCheckingAssumptions::new(param_env);
+    if let Err(e) = ocx.resolve_regions_and_report_errors(local_id, &assumptions) {
         return Err(e);
     }
 

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -8,10 +8,8 @@ use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId, LocalModDefId};
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::ItemKind;
-use rustc_infer::infer::outlives::env::{OutlivesEnvironment, RegionBoundPairs};
-use rustc_infer::infer::outlives::obligations::TypeOutlives;
+use rustc_infer::infer::outlives::env::RegionCheckingAssumptions;
 use rustc_infer::infer::{self, InferCtxt, TyCtxtInferExt};
-use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::trait_def::TraitSpecializationKind;
 use rustc_middle::ty::{
@@ -23,6 +21,7 @@ use rustc_session::parse::feature_err;
 use rustc_span::symbol::{sym, Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
 use rustc_target::spec::abi::Abi;
+use rustc_trait_selection::regions::InferCtxtRegionExt;
 use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt;
 use rustc_trait_selection::traits::misc::{
     type_allowed_to_implement_const_param_ty, ConstParamTyImplementationError,
@@ -126,9 +125,9 @@ where
         }
     }
 
-    let outlives_env = OutlivesEnvironment::with_bounds(param_env, implied_bounds);
+    let assumptions = RegionCheckingAssumptions::with_bounds(param_env, implied_bounds);
 
-    wfcx.ocx.resolve_regions_and_report_errors(body_def_id, &outlives_env)?;
+    wfcx.ocx.resolve_regions_and_report_errors(body_def_id, &assumptions)?;
     infcx.tainted_by_errors().error_reported()
 }
 
@@ -673,10 +672,12 @@ fn ty_known_to_outlive<'tcx>(
     ty: Ty<'tcx>,
     region: ty::Region<'tcx>,
 ) -> bool {
-    resolve_regions_with_wf_tys(tcx, id, param_env, wf_tys, |infcx, region_bound_pairs| {
-        let origin = infer::RelateParamBound(DUMMY_SP, ty, None);
-        let outlives = &mut TypeOutlives::new(infcx, tcx, region_bound_pairs, None, param_env);
-        outlives.type_must_outlive(origin, ty, region, ConstraintCategory::BoringNoLocation);
+    test_region_obligations(tcx, id, param_env, wf_tys, |infcx| {
+        infcx.register_region_obligation(infer::RegionObligation {
+            sub_region: region,
+            sup_type: ty,
+            origin: infer::RelateParamBound(DUMMY_SP, ty, None),
+        });
     })
 }
 
@@ -690,42 +691,34 @@ fn region_known_to_outlive<'tcx>(
     region_a: ty::Region<'tcx>,
     region_b: ty::Region<'tcx>,
 ) -> bool {
-    resolve_regions_with_wf_tys(tcx, id, param_env, wf_tys, |mut infcx, _| {
-        use rustc_infer::infer::outlives::obligations::TypeOutlivesDelegate;
-        let origin = infer::RelateRegionParamBound(DUMMY_SP);
-        // `region_a: region_b` -> `region_b <= region_a`
-        infcx.push_sub_region_constraint(
-            origin,
-            region_b,
-            region_a,
-            ConstraintCategory::BoringNoLocation,
-        );
+    test_region_obligations(tcx, id, param_env, wf_tys, |infcx| {
+        infcx.sub_regions(infer::RelateRegionParamBound(DUMMY_SP), region_b, region_a);
     })
 }
 
 /// Given a known `param_env` and a set of well formed types, set up an
 /// `InferCtxt`, call the passed function (to e.g. set up region constraints
 /// to be tested), then resolve region and return errors
-fn resolve_regions_with_wf_tys<'tcx>(
+fn test_region_obligations<'tcx>(
     tcx: TyCtxt<'tcx>,
     id: LocalDefId,
     param_env: ty::ParamEnv<'tcx>,
     wf_tys: &FxIndexSet<Ty<'tcx>>,
-    add_constraints: impl for<'a> FnOnce(&'a InferCtxt<'tcx>, &'a RegionBoundPairs<'tcx>),
+    add_constraints: impl FnOnce(&InferCtxt<'tcx>),
 ) -> bool {
     // Unfortunately, we have to use a new `InferCtxt` each call, because
     // region constraints get added and solved there and we need to test each
     // call individually.
     let infcx = tcx.infer_ctxt().build();
-    let outlives_environment = OutlivesEnvironment::with_bounds(
+
+    add_constraints(&infcx);
+
+    let outlives_environment = RegionCheckingAssumptions::with_bounds(
         param_env,
         infcx.implied_bounds_tys(param_env, id, wf_tys.clone()),
     );
-    let region_bound_pairs = outlives_environment.region_bound_pairs();
-
-    add_constraints(&infcx, region_bound_pairs);
 
-    let errors = infcx.resolve_regions(&outlives_environment);
+    let errors = infcx.resolve_regions_normalizing_outlives_obligations(&outlives_environment);
     debug!(?errors, "errors");
 
     // If we were able to prove that the type outlives the region without