Normalize type outlives obligations in NLL for new solver

compiler/rustc_borrowck/src/type_check/constraint_conversion.rs

@@ -5,10 +5,13 @@ use rustc_infer::infer::outlives::obligations::{TypeOutlives, TypeOutlivesDelega
 use rustc_infer::infer::region_constraints::{GenericKind, VerifyBound};
 use rustc_infer::infer::{self, InferCtxt, SubregionOrigin};
 use rustc_middle::mir::{ClosureOutlivesSubject, ClosureRegionRequirements, ConstraintCategory};
-use rustc_middle::ty::GenericArgKind;
-use rustc_middle::ty::{self, TyCtxt};
-use rustc_middle::ty::{TypeFoldable, TypeVisitableExt};
+use rustc_middle::traits::query::NoSolution;
+use rustc_middle::traits::ObligationCause;
+use rustc_middle::ty::{self, GenericArgKind, Ty, TyCtxt, TypeFoldable, TypeVisitableExt};
 use rustc_span::{Span, DUMMY_SP};
+use rustc_trait_selection::solve::deeply_normalize;
+use rustc_trait_selection::traits::query::type_op::custom::CustomTypeOp;
+use rustc_trait_selection::traits::query::type_op::{TypeOp, TypeOpOutput};
 
 use crate::{
     constraints::OutlivesConstraint,
@@ -33,6 +36,7 @@ pub(crate) struct ConstraintConversion<'a, 'tcx> {
     /// our special inference variable there, we would mess that up.
     region_bound_pairs: &'a RegionBoundPairs<'tcx>,
     implicit_region_bound: ty::Region<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
     known_type_outlives_obligations: &'tcx [ty::PolyTypeOutlivesPredicate<'tcx>],
     locations: Locations,
     span: Span,
@@ -47,6 +51,7 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
         universal_regions: &'a UniversalRegions<'tcx>,
         region_bound_pairs: &'a RegionBoundPairs<'tcx>,
         implicit_region_bound: ty::Region<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
         known_type_outlives_obligations: &'tcx [ty::PolyTypeOutlivesPredicate<'tcx>],
         locations: Locations,
         span: Span,
@@ -59,6 +64,7 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
             universal_regions,
             region_bound_pairs,
             implicit_region_bound,
+            param_env,
             known_type_outlives_obligations,
             locations,
             span,
@@ -137,36 +143,68 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
         // Extract out various useful fields we'll need below.
         let ConstraintConversion {
             tcx,
+            infcx,
             region_bound_pairs,
             implicit_region_bound,
             known_type_outlives_obligations,
             ..
         } = *self;
 
-        let ty::OutlivesPredicate(k1, r2) = predicate;
-        match k1.unpack() {
-            GenericArgKind::Lifetime(r1) => {
-                let r1_vid = self.to_region_vid(r1);
-                let r2_vid = self.to_region_vid(r2);
-                self.add_outlives(r1_vid, r2_vid, constraint_category);
+        let mut outlives_predicates = vec![(predicate, constraint_category)];
+        for iteration in 0.. {
+            if outlives_predicates.is_empty() {
+                break;
+            }
+
+            if !self.tcx.recursion_limit().value_within_limit(iteration) {
+                bug!(
+                    "FIXME(-Znext-solver): Overflowed when processing region obligations: {outlives_predicates:#?}"
+                );
             }
 
-            GenericArgKind::Type(t1) => {
-                // we don't actually use this for anything, but
-                // the `TypeOutlives` code needs an origin.
-                let origin = infer::RelateParamBound(DUMMY_SP, t1, None);
+            let mut next_outlives_predicates = vec![];
+            for (ty::OutlivesPredicate(k1, r2), constraint_category) in outlives_predicates {
+                match k1.unpack() {
+                    GenericArgKind::Lifetime(r1) => {
+                        let r1_vid = self.to_region_vid(r1);
+                        let r2_vid = self.to_region_vid(r2);
+                        self.add_outlives(r1_vid, r2_vid, constraint_category);
+                    }
 
-                TypeOutlives::new(
-                    &mut *self,
-                    tcx,
-                    region_bound_pairs,
-                    Some(implicit_region_bound),
-                    known_type_outlives_obligations,
-                )
-                .type_must_outlive(origin, t1, r2, constraint_category);
+                    GenericArgKind::Type(mut t1) => {
+                        // Normalize the type we receive from a `TypeOutlives` obligation
+                        // in the new trait solver.
+                        if infcx.next_trait_solver() {
+                            t1 = self.normalize_and_add_type_outlives_constraints(
+                                t1,
+                                &mut next_outlives_predicates,
+                            );
+                        }
+
+                        // we don't actually use this for anything, but
+                        // the `TypeOutlives` code needs an origin.
+                        let origin = infer::RelateParamBound(DUMMY_SP, t1, None);
+
+                        TypeOutlives::new(
+                            &mut *self,
+                            tcx,
+                            region_bound_pairs,
+                            Some(implicit_region_bound),
+                            known_type_outlives_obligations,
+                        )
+                        .type_must_outlive(
+                            origin,
+                            t1,
+                            r2,
+                            constraint_category,
+                        );
+                    }
+
+                    GenericArgKind::Const(_) => unreachable!(),
+                }
             }
 
-            GenericArgKind::Const(_) => unreachable!(),
+            outlives_predicates = next_outlives_predicates;
         }
     }
 
@@ -232,6 +270,42 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
         debug!("add_type_test(type_test={:?})", type_test);
         self.constraints.type_tests.push(type_test);
     }
+
+    fn normalize_and_add_type_outlives_constraints(
+        &self,
+        ty: Ty<'tcx>,
+        next_outlives_predicates: &mut Vec<(
+            ty::OutlivesPredicate<ty::GenericArg<'tcx>, ty::Region<'tcx>>,
+            ConstraintCategory<'tcx>,
+        )>,
+    ) -> Ty<'tcx> {
+        let result = CustomTypeOp::new(
+            |ocx| {
+                deeply_normalize(
+                    ocx.infcx.at(&ObligationCause::dummy_with_span(self.span), self.param_env),
+                    ty,
+                )
+                .map_err(|_| NoSolution)
+            },
+            "normalize type outlives obligation",
+        )
+        .fully_perform(self.infcx, self.span);
+
+        match result {
+            Ok(TypeOpOutput { output: ty, constraints, .. }) => {
+                if let Some(constraints) = constraints {
+                    assert!(
+                        constraints.member_constraints.is_empty(),
+                        "no member constraints expected from normalizing: {:#?}",
+                        constraints.member_constraints
+                    );
+                    next_outlives_predicates.extend(constraints.outlives.iter().copied());
+                }
+                ty
+            }
+            Err(_) => ty,
+        }
+    }
 }
 
 impl<'a, 'b, 'tcx> TypeOutlivesDelegate<'tcx> for &'a mut ConstraintConversion<'b, 'tcx> {

compiler/rustc_borrowck/src/type_check/free_region_relations.rs

@@ -8,8 +8,11 @@ use rustc_infer::infer::region_constraints::GenericKind;
 use rustc_infer::infer::InferCtxt;
 use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::traits::query::OutlivesBound;
+use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::{self, RegionVid, Ty, TypeVisitableExt};
-use rustc_span::{ErrorGuaranteed, Span, DUMMY_SP};
+use rustc_span::{ErrorGuaranteed, DUMMY_SP};
+use rustc_trait_selection::solve::deeply_normalize;
+use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt;
 use rustc_trait_selection::traits::query::type_op::{self, TypeOp};
 use std::rc::Rc;
 use type_op::TypeOpOutput;
@@ -52,15 +55,13 @@ pub(crate) struct CreateResult<'tcx> {
 pub(crate) fn create<'tcx>(
     infcx: &InferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
-    known_type_outlives_obligations: &'tcx [ty::PolyTypeOutlivesPredicate<'tcx>],
     implicit_region_bound: ty::Region<'tcx>,
     universal_regions: &Rc<UniversalRegions<'tcx>>,
     constraints: &mut MirTypeckRegionConstraints<'tcx>,
 ) -> CreateResult<'tcx> {
     UniversalRegionRelationsBuilder {
         infcx,
         param_env,
-        known_type_outlives_obligations,
         implicit_region_bound,
         constraints,
         universal_regions: universal_regions.clone(),
@@ -178,7 +179,6 @@ impl UniversalRegionRelations<'_> {
 struct UniversalRegionRelationsBuilder<'this, 'tcx> {
     infcx: &'this InferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
-    known_type_outlives_obligations: &'tcx [ty::PolyTypeOutlivesPredicate<'tcx>],
     universal_regions: Rc<UniversalRegions<'tcx>>,
     implicit_region_bound: ty::Region<'tcx>,
     constraints: &'this mut MirTypeckRegionConstraints<'tcx>,
@@ -222,6 +222,32 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
             self.relate_universal_regions(fr, fr_fn_body);
         }
 
+        // Normalize the assumptions we use to borrowck the program.
+        let mut constraints = vec![];
+        let mut known_type_outlives_obligations = vec![];
+        for bound in param_env.caller_bounds() {
+            let Some(mut outlives) = bound.as_type_outlives_clause() else { continue };
+
+            // In the new solver, normalize the type-outlives obligation assumptions.
+            if self.infcx.next_trait_solver() {
+                match deeply_normalize(
+                    self.infcx.at(&ObligationCause::misc(span, defining_ty_def_id), self.param_env),
+                    outlives,
+                ) {
+                    Ok(normalized_outlives) => {
+                        outlives = normalized_outlives;
+                    }
+                    Err(e) => {
+                        self.infcx.err_ctxt().report_fulfillment_errors(e);
+                    }
+                }
+            }
+
+            known_type_outlives_obligations.push(outlives);
+        }
+        let known_type_outlives_obligations =
+            self.infcx.tcx.arena.alloc_slice(&known_type_outlives_obligations);
+
         let unnormalized_input_output_tys = self
             .universal_regions
             .unnormalized_input_tys
@@ -239,7 +265,6 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
         //   the `relations` is built.
         let mut normalized_inputs_and_output =
             Vec::with_capacity(self.universal_regions.unnormalized_input_tys.len() + 1);
-        let mut constraints = vec![];
         for ty in unnormalized_input_output_tys {
             debug!("build: input_or_output={:?}", ty);
             // We add implied bounds from both the unnormalized and normalized ty.
@@ -304,7 +329,19 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
         }
 
         for c in constraints {
-            self.push_region_constraints(c, span);
+            constraint_conversion::ConstraintConversion::new(
+                self.infcx,
+                &self.universal_regions,
+                &self.region_bound_pairs,
+                self.implicit_region_bound,
+                param_env,
+                known_type_outlives_obligations,
+                Locations::All(span),
+                span,
+                ConstraintCategory::Internal,
+                self.constraints,
+            )
+            .convert_all(c);
         }
 
         CreateResult {
@@ -313,30 +350,12 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
                 outlives: self.outlives.freeze(),
                 inverse_outlives: self.inverse_outlives.freeze(),
             }),
-            known_type_outlives_obligations: self.known_type_outlives_obligations,
+            known_type_outlives_obligations,
             region_bound_pairs: self.region_bound_pairs,
             normalized_inputs_and_output,
         }
     }
 
-    #[instrument(skip(self, data), level = "debug")]
-    fn push_region_constraints(&mut self, data: &QueryRegionConstraints<'tcx>, span: Span) {
-        debug!("constraints generated: {:#?}", data);
-
-        constraint_conversion::ConstraintConversion::new(
-            self.infcx,
-            &self.universal_regions,
-            &self.region_bound_pairs,
-            self.implicit_region_bound,
-            self.known_type_outlives_obligations,
-            Locations::All(span),
-            span,
-            ConstraintCategory::Internal,
-            self.constraints,
-        )
-        .convert_all(data);
-    }
-
     /// Update the type of a single local, which should represent
     /// either the return type of the MIR or one of its arguments. At
     /// the same time, compute and add any implied bounds that come

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -156,10 +156,6 @@ pub(crate) fn type_check<'mir, 'tcx>(
     } = free_region_relations::create(
         infcx,
         param_env,
-        // FIXME(-Znext-solver): These are unnormalized. Normalize them.
-        infcx.tcx.arena.alloc_from_iter(
-            param_env.caller_bounds().iter().filter_map(|clause| clause.as_type_outlives_clause()),
-        ),
         implicit_region_bound,
         universal_regions,
         &mut constraints,
@@ -1136,6 +1132,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             self.borrowck_context.universal_regions,
             self.region_bound_pairs,
             self.implicit_region_bound,
+            self.param_env,
             self.known_type_outlives_obligations,
             locations,
             locations.span(self.body),
@@ -2740,6 +2737,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 self.borrowck_context.universal_regions,
                 self.region_bound_pairs,
                 self.implicit_region_bound,
+                self.param_env,
                 self.known_type_outlives_obligations,
                 locations,
                 DUMMY_SP,                   // irrelevant; will be overridden.

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

@@ -71,6 +71,7 @@ use rustc_hir::lang_items::LangItem;
 use rustc_middle::dep_graph::DepContext;
 use rustc_middle::ty::print::{with_forced_trimmed_paths, PrintError};
 use rustc_middle::ty::relate::{self, RelateResult, TypeRelation};
+use rustc_middle::ty::ToPredicate;
 use rustc_middle::ty::{
     self, error::TypeError, IsSuggestable, List, Region, Ty, TyCtxt, TypeFoldable,
     TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
@@ -519,10 +520,12 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                         self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
                     }
 
-                    RegionResolutionError::CannotNormalize(ty, origin) => {
+                    RegionResolutionError::CannotNormalize(clause, origin) => {
+                        let clause: ty::Clause<'tcx> =
+                            clause.map_bound(ty::ClauseKind::TypeOutlives).to_predicate(self.tcx);
                         self.tcx
                             .dcx()
-                            .struct_span_err(origin.span(), format!("cannot normalize `{ty}`"))
+                            .struct_span_err(origin.span(), format!("cannot normalize `{clause}`"))
                             .emit();
                     }
                 }

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

@@ -99,7 +99,7 @@ pub enum RegionResolutionError<'tcx> {
         Region<'tcx>,          // the placeholder `'b`
     ),
 
-    CannotNormalize(Ty<'tcx>, SubregionOrigin<'tcx>),
+    CannotNormalize(ty::PolyTypeOutlivesPredicate<'tcx>, SubregionOrigin<'tcx>),
 }
 
 impl<'tcx> RegionResolutionError<'tcx> {

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

@@ -4,8 +4,8 @@ use super::region_constraints::RegionConstraintData;
 use super::{InferCtxt, RegionResolutionError, SubregionOrigin};
 use crate::infer::free_regions::RegionRelations;
 use crate::infer::lexical_region_resolve;
-use rustc_middle::traits::query::OutlivesBound;
-use rustc_middle::ty::{self, Ty};
+use rustc_middle::traits::query::{NoSolution, OutlivesBound};
+use rustc_middle::ty;
 
 pub mod components;
 pub mod env;
@@ -49,12 +49,15 @@ impl<'tcx> InferCtxt<'tcx> {
     pub fn resolve_regions_with_normalize(
         &self,
         outlives_env: &OutlivesEnvironment<'tcx>,
-        deeply_normalize_ty: impl Fn(Ty<'tcx>, SubregionOrigin<'tcx>) -> Result<Ty<'tcx>, Ty<'tcx>>,
+        deeply_normalize_ty: impl Fn(
+            ty::PolyTypeOutlivesPredicate<'tcx>,
+            SubregionOrigin<'tcx>,
+        ) -> Result<ty::PolyTypeOutlivesPredicate<'tcx>, NoSolution>,
     ) -> Vec<RegionResolutionError<'tcx>> {
         match self.process_registered_region_obligations(outlives_env, deeply_normalize_ty) {
             Ok(()) => {}
-            Err((ty, origin)) => {
-                return vec![RegionResolutionError::CannotNormalize(ty, origin)];
+            Err((clause, origin)) => {
+                return vec![RegionResolutionError::CannotNormalize(clause, origin)];
             }
         };