Apply suggestions from review

11 files changed, 77 insertions, 50 deletions

diff --git a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
index 02ef7357d66..52559f9039b 100644
--- a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
+++ b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
@@ -33,7 +33,7 @@ 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,
     category: ConstraintCategory<'tcx>,
@@ -47,7 +47,7 @@ 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,
         category: ConstraintCategory<'tcx>,
@@ -59,7 +59,7 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
             universal_regions,
             region_bound_pairs,
             implicit_region_bound,
-            param_env,
+            known_type_outlives_obligations,
             locations,
             span,
             category,
@@ -136,7 +136,11 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
 
         // Extract out various useful fields we'll need below.
         let ConstraintConversion {
-            tcx, region_bound_pairs, implicit_region_bound, param_env, ..
+            tcx,
+            region_bound_pairs,
+            implicit_region_bound,
+            known_type_outlives_obligations,
+            ..
         } = *self;
 
         let ty::OutlivesPredicate(k1, r2) = predicate;
@@ -157,8 +161,7 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
                     tcx,
                     region_bound_pairs,
                     Some(implicit_region_bound),
-                    // FIXME(-Znext-solver): These bounds are not normalized!
-                    param_env.caller_bounds(),
+                    known_type_outlives_obligations,
                 )
                 .type_must_outlive(origin, t1, r2, constraint_category);
             }
diff --git a/compiler/rustc_borrowck/src/type_check/free_region_relations.rs b/compiler/rustc_borrowck/src/type_check/free_region_relations.rs
index 011b5b760c2..d518f54fd25 100644
--- a/compiler/rustc_borrowck/src/type_check/free_region_relations.rs
+++ b/compiler/rustc_borrowck/src/type_check/free_region_relations.rs
@@ -45,12 +45,14 @@ type NormalizedInputsAndOutput<'tcx> = Vec<Ty<'tcx>>;
 pub(crate) struct CreateResult<'tcx> {
     pub(crate) universal_region_relations: Frozen<UniversalRegionRelations<'tcx>>,
     pub(crate) region_bound_pairs: RegionBoundPairs<'tcx>,
+    pub(crate) known_type_outlives_obligations: &'tcx [ty::PolyTypeOutlivesPredicate<'tcx>],
     pub(crate) normalized_inputs_and_output: NormalizedInputsAndOutput<'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>,
@@ -58,6 +60,7 @@ pub(crate) fn create<'tcx>(
     UniversalRegionRelationsBuilder {
         infcx,
         param_env,
+        known_type_outlives_obligations,
         implicit_region_bound,
         constraints,
         universal_regions: universal_regions.clone(),
@@ -175,6 +178,7 @@ 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>,
@@ -200,7 +204,8 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
         let defining_ty_def_id = self.universal_regions.defining_ty.def_id().expect_local();
         let span = tcx.def_span(defining_ty_def_id);
 
-        // Insert the facts we know from the predicates. Why? Why not.
+        // Insert the `'a: 'b` we know from the predicates.
+        // This does not consider the type-outlives.
         let param_env = self.param_env;
         self.add_outlives_bounds(outlives::explicit_outlives_bounds(param_env));
 
@@ -308,6 +313,7 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
                 outlives: self.outlives.freeze(),
                 inverse_outlives: self.inverse_outlives.freeze(),
             }),
+            known_type_outlives_obligations: self.known_type_outlives_obligations,
             region_bound_pairs: self.region_bound_pairs,
             normalized_inputs_and_output,
         }
@@ -322,7 +328,7 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
             &self.universal_regions,
             &self.region_bound_pairs,
             self.implicit_region_bound,
-            self.param_env,
+            self.known_type_outlives_obligations,
             Locations::All(span),
             span,
             ConstraintCategory::Internal,
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 488dfc64cf6..59c4d9a6c78 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -152,9 +152,14 @@ pub(crate) fn type_check<'mir, 'tcx>(
         universal_region_relations,
         region_bound_pairs,
         normalized_inputs_and_output,
+        known_type_outlives_obligations,
     } = 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,
@@ -176,6 +181,7 @@ pub(crate) fn type_check<'mir, 'tcx>(
         body,
         param_env,
         &region_bound_pairs,
+        known_type_outlives_obligations,
         implicit_region_bound,
         &mut borrowck_context,
     );
@@ -850,6 +856,7 @@ struct TypeChecker<'a, 'tcx> {
     /// all of the promoted items.
     user_type_annotations: &'a CanonicalUserTypeAnnotations<'tcx>,
     region_bound_pairs: &'a RegionBoundPairs<'tcx>,
+    known_type_outlives_obligations: &'tcx [ty::PolyTypeOutlivesPredicate<'tcx>],
     implicit_region_bound: ty::Region<'tcx>,
     reported_errors: FxIndexSet<(Ty<'tcx>, Span)>,
     borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>,
@@ -1000,6 +1007,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         body: &'a Body<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         region_bound_pairs: &'a RegionBoundPairs<'tcx>,
+        known_type_outlives_obligations: &'tcx [ty::PolyTypeOutlivesPredicate<'tcx>],
         implicit_region_bound: ty::Region<'tcx>,
         borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>,
     ) -> Self {
@@ -1010,6 +1018,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             user_type_annotations: &body.user_type_annotations,
             param_env,
             region_bound_pairs,
+            known_type_outlives_obligations,
             implicit_region_bound,
             borrowck_context,
             reported_errors: Default::default(),
@@ -1127,7 +1136,7 @@ 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),
             category,
@@ -2731,7 +2740,7 @@ 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.
                 ConstraintCategory::Boring, // same as above.
diff --git a/compiler/rustc_hir_analysis/src/check/dropck.rs b/compiler/rustc_hir_analysis/src/check/dropck.rs
index 3d2d667763a..7b60457affa 100644
--- a/compiler/rustc_hir_analysis/src/check/dropck.rs
+++ b/compiler/rustc_hir_analysis/src/check/dropck.rs
@@ -189,7 +189,7 @@ 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!(),
+                RegionResolutionError::CannotNormalize(..) => unreachable!(),
             };
             guar = Some(
                 struct_span_code_err!(
diff --git a/compiler/rustc_infer/src/infer/outlives/mod.rs b/compiler/rustc_infer/src/infer/outlives/mod.rs
index 97ab2f32c40..926e198b219 100644
--- a/compiler/rustc_infer/src/infer/outlives/mod.rs
+++ b/compiler/rustc_infer/src/infer/outlives/mod.rs
@@ -1,7 +1,7 @@
 //! Various code related to computing outlives relations.
 use self::env::OutlivesEnvironment;
 use super::region_constraints::RegionConstraintData;
-use super::{InferCtxt, RegionResolutionError};
+use super::{InferCtxt, RegionResolutionError, SubregionOrigin};
 use crate::infer::free_regions::RegionRelations;
 use crate::infer::lexical_region_resolve;
 use rustc_middle::traits::query::OutlivesBound;
@@ -42,14 +42,14 @@ impl<'tcx> InferCtxt<'tcx> {
     /// done -- or the compiler will panic -- but it is legal to use
     /// `resolve_vars_if_possible` as well as `fully_resolve`.
     ///
-    /// If you are in a crate that has access to `rustc_trai_selection`,
-    /// then it's probably better to use `resolve_regions_normalizing_outlives_obligations`,
+    /// If you are in a crate that has access to `rustc_trait_selection`,
+    /// then it's probably better to use `resolve_regions`,
     /// which knows how to normalize registered region obligations.
     #[must_use]
     pub fn resolve_regions_with_normalize(
         &self,
         outlives_env: &OutlivesEnvironment<'tcx>,
-        deeply_normalize_ty: impl Fn(Ty<'tcx>) -> Result<Ty<'tcx>, Ty<'tcx>>,
+        deeply_normalize_ty: impl Fn(Ty<'tcx>, SubregionOrigin<'tcx>) -> Result<Ty<'tcx>, Ty<'tcx>>,
     ) -> Vec<RegionResolutionError<'tcx>> {
         match self.process_registered_region_obligations(outlives_env, deeply_normalize_ty) {
             Ok(()) => {}
diff --git a/compiler/rustc_infer/src/infer/outlives/obligations.rs b/compiler/rustc_infer/src/infer/outlives/obligations.rs
index bc66522a8b6..b10bf98e8b5 100644
--- a/compiler/rustc_infer/src/infer/outlives/obligations.rs
+++ b/compiler/rustc_infer/src/infer/outlives/obligations.rs
@@ -68,8 +68,8 @@ use crate::infer::{
 use crate::traits::{ObligationCause, ObligationCauseCode};
 use rustc_data_structures::undo_log::UndoLogs;
 use rustc_middle::mir::ConstraintCategory;
+use rustc_middle::ty::GenericArgKind;
 use rustc_middle::ty::{self, GenericArgsRef, Region, Ty, TyCtxt, TypeVisitableExt};
-use rustc_middle::ty::{GenericArgKind, ToPredicate};
 use rustc_span::DUMMY_SP;
 use smallvec::smallvec;
 
@@ -128,7 +128,7 @@ impl<'tcx> InferCtxt<'tcx> {
     pub fn process_registered_region_obligations<E>(
         &self,
         outlives_env: &OutlivesEnvironment<'tcx>,
-        mut deeply_normalize_ty: impl FnMut(Ty<'tcx>) -> Result<Ty<'tcx>, E>,
+        mut deeply_normalize_ty: impl FnMut(Ty<'tcx>, SubregionOrigin<'tcx>) -> Result<Ty<'tcx>, E>,
     ) -> Result<(), (E, SubregionOrigin<'tcx>)> {
         assert!(!self.in_snapshot(), "cannot process registered region obligations in a snapshot");
 
@@ -141,20 +141,23 @@ impl<'tcx> InferCtxt<'tcx> {
                 let ty::ClauseKind::TypeOutlives(outlives) = bound_clause.skip_binder() else {
                     return None;
                 };
-                Some(deeply_normalize_ty(outlives.0).map(|ty| {
-                    bound_clause
-                        .rebind(ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(ty, outlives.1)))
-                        .to_predicate(self.tcx)
-                }))
+                Some(
+                    deeply_normalize_ty(
+                        outlives.0,
+                        SubregionOrigin::AscribeUserTypeProvePredicate(DUMMY_SP),
+                    )
+                    .map(|ty| bound_clause.rebind(ty::OutlivesPredicate(ty, outlives.1))),
+                )
             })
-            // FIXME: How do we accurately report an error here :(
+            // FIXME(-Znext-solver): How do we accurately report an error here :(
             .try_collect()
             .map_err(|e| (e, SubregionOrigin::AscribeUserTypeProvePredicate(DUMMY_SP)))?;
 
         let my_region_obligations = self.take_registered_region_obligations();
 
         for RegionObligation { sup_type, sub_region, origin } in my_region_obligations {
-            let sup_type = deeply_normalize_ty(sup_type).map_err(|e| (e, origin.clone()))?;
+            let sup_type =
+                deeply_normalize_ty(sup_type, origin.clone()).map_err(|e| (e, origin.clone()))?;
             debug!(?sup_type, ?sub_region, ?origin);
 
             let outlives = &mut TypeOutlives::new(
@@ -216,7 +219,7 @@ where
         tcx: TyCtxt<'tcx>,
         region_bound_pairs: &'cx RegionBoundPairs<'tcx>,
         implicit_region_bound: Option<ty::Region<'tcx>>,
-        caller_bounds: &'cx [ty::Clause<'tcx>],
+        caller_bounds: &'cx [ty::PolyTypeOutlivesPredicate<'tcx>],
     ) -> Self {
         Self {
             delegate,
diff --git a/compiler/rustc_infer/src/infer/outlives/verify.rs b/compiler/rustc_infer/src/infer/outlives/verify.rs
index 2ad8b6b98e3..5d2f51c689b 100644
--- a/compiler/rustc_infer/src/infer/outlives/verify.rs
+++ b/compiler/rustc_infer/src/infer/outlives/verify.rs
@@ -23,7 +23,7 @@ pub struct VerifyBoundCx<'cx, 'tcx> {
     /// Outside of borrowck the only way to prove `T: '?0` is by
     /// setting  `'?0` to `'empty`.
     implicit_region_bound: Option<ty::Region<'tcx>>,
-    caller_bounds: &'cx [ty::Clause<'tcx>],
+    caller_bounds: &'cx [ty::PolyTypeOutlivesPredicate<'tcx>],
 }
 
 impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
@@ -31,7 +31,7 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
         tcx: TyCtxt<'tcx>,
         region_bound_pairs: &'cx RegionBoundPairs<'tcx>,
         implicit_region_bound: Option<ty::Region<'tcx>>,
-        caller_bounds: &'cx [ty::Clause<'tcx>],
+        caller_bounds: &'cx [ty::PolyTypeOutlivesPredicate<'tcx>],
     ) -> Self {
         Self { tcx, region_bound_pairs, implicit_region_bound, caller_bounds }
     }
@@ -219,8 +219,9 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
         // To start, collect bounds from user environment. Note that
         // parameter environments are already elaborated, so we don't
         // have to worry about that.
-        let param_bounds =
-            self.collect_outlives_from_clause_list(erased_ty, self.caller_bounds.iter().copied());
+        let param_bounds = self.caller_bounds.iter().copied().filter(move |outlives_predicate| {
+            super::test_type_match::can_match_erased_ty(tcx, *outlives_predicate, erased_ty)
+        });
 
         // Next, collect regions we scraped from the well-formedness
         // constraints in the fn signature. To do that, we walk the list
@@ -307,22 +308,4 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
             .filter_map(|p| p.no_bound_vars())
             .map(|OutlivesPredicate(_, r)| r)
     }
-
-    /// Searches through a predicate list for a predicate `T: 'a`.
-    ///
-    /// Careful: does not elaborate predicates, and just uses `==`
-    /// when comparing `ty` for equality, so `ty` must be something
-    /// that does not involve inference variables and where you
-    /// otherwise want a precise match.
-    fn collect_outlives_from_clause_list(
-        &self,
-        erased_ty: Ty<'tcx>,
-        clauses: impl Iterator<Item = ty::Clause<'tcx>>,
-    ) -> impl Iterator<Item = ty::Binder<'tcx, ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>>>
-    {
-        let tcx = self.tcx;
-        clauses.filter_map(|p| p.as_type_outlives_clause()).filter(move |outlives_predicate| {
-            super::test_type_match::can_match_erased_ty(tcx, *outlives_predicate, erased_ty)
-        })
-    }
 }
diff --git a/compiler/rustc_trait_selection/src/regions.rs b/compiler/rustc_trait_selection/src/regions.rs
index 3c53da32d0a..e8929f114e1 100644
--- a/compiler/rustc_trait_selection/src/regions.rs
+++ b/compiler/rustc_trait_selection/src/regions.rs
@@ -20,12 +20,15 @@ impl<'tcx> InferCtxtRegionExt<'tcx> for InferCtxt<'tcx> {
         &self,
         outlives_env: &OutlivesEnvironment<'tcx>,
     ) -> Vec<RegionResolutionError<'tcx>> {
-        self.resolve_regions(outlives_env, |ty| {
+        self.resolve_regions_with_normalize(outlives_env, |ty, origin| {
             let ty = self.resolve_vars_if_possible(ty);
 
             if self.next_trait_solver() {
                 crate::solve::deeply_normalize(
-                    self.at(&ObligationCause::dummy(), outlives_env.param_env),
+                    self.at(
+                        &ObligationCause::dummy_with_span(origin.span()),
+                        outlives_env.param_env,
+                    ),
                     ty,
                 )
                 .map_err(|_| ty)
diff --git a/compiler/rustc_trait_selection/src/traits/auto_trait.rs b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
index 87b68a8bd2d..b258007787d 100644
--- a/compiler/rustc_trait_selection/src/traits/auto_trait.rs
+++ b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
@@ -179,7 +179,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
         }
 
         let outlives_env = OutlivesEnvironment::new(full_env);
-        let _ = infcx.process_registered_region_obligations::<!>(&outlives_env, |ty| Ok(ty));
+        let _ = infcx.process_registered_region_obligations::<!>(&outlives_env, |ty, _| Ok(ty));
 
         let region_data =
             infcx.inner.borrow_mut().unwrap_region_constraints().region_constraint_data().clone();
diff --git a/tests/ui/traits/next-solver/unsound-region-obligation.rs b/tests/ui/traits/next-solver/unsound-region-obligation.rs
new file mode 100644
index 00000000000..b8bfa035388
--- /dev/null
+++ b/tests/ui/traits/next-solver/unsound-region-obligation.rs
@@ -0,0 +1,13 @@
+//~ ERROR the type `<() as StaticTy>::Item<'a>` does not fulfill the required lifetime
+// compile-flags: -Znext-solver
+// Regression test for rust-lang/trait-system-refactor-initiative#59
+
+trait StaticTy {
+    type Item<'a>: 'static;
+}
+
+impl StaticTy for () {
+    type Item<'a> = &'a ();
+}
+
+fn main() {}
diff --git a/tests/ui/traits/next-solver/unsound-region-obligation.stderr b/tests/ui/traits/next-solver/unsound-region-obligation.stderr
new file mode 100644
index 00000000000..518de7ea3e0
--- /dev/null
+++ b/tests/ui/traits/next-solver/unsound-region-obligation.stderr
@@ -0,0 +1,7 @@
+error[E0477]: the type `<() as StaticTy>::Item<'a>` does not fulfill the required lifetime
+   |
+   = note: type must satisfy the static lifetime
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0477`.