Auto merge of rust-lang#120513 - compiler-errors:normalize-regions-for-nll, r=<try>

Normalize type outlives obligations in NLL for new solver

Normalize the type outlives assumptions and obligations in MIR borrowck. This should fix any of the lazy-norm-related MIR borrowck problems.

Also some cleanups from last PR:
1. Normalize obligations in a loop in lexical region resolution
2. Use `deeply_normalize_with_skipped_universes` in lexical resolution since we may have, e.g. `for<'a> Alias<'a>: 'b`.

r? lcnr

Author: bors

compiler/rustc_borrowck/src/type_check/constraint_conversion.rs

@@ -5,10 +5,15 @@ 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::traits::ObligationCause;
 use rustc_middle::ty::GenericArgKind;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_middle::ty::{TypeFoldable, TypeVisitableExt};
 use rustc_span::{Span, 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::custom::CustomTypeOp;
+use rustc_trait_selection::traits::query::type_op::{TypeOp, TypeOpOutput};
 
 use crate::{
     constraints::OutlivesConstraint,
@@ -33,6 +38,7 @@ 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 +53,7 @@ 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 +66,7 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
             universal_regions,
             region_bound_pairs,
             implicit_region_bound,
+            param_env,
             known_type_outlives_obligations,
             locations,
             span,
@@ -137,36 +145,83 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
         // Extract out various useful fields we'll need below.
         let ConstraintConversion {
             tcx,
+            infcx,
+            param_env,
             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)];
+        while let Some((ty::OutlivesPredicate(k1, r2), constraint_category)) =
+            outlives_predicates.pop()
+        {
+            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);
+                }
 
-            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);
+                GenericArgKind::Type(mut t1) => {
+                    // Normalize the type we receive from a `TypeOutlives` obligation
+                    // in the new trait solver.
+                    if infcx.next_trait_solver() {
+                        let result = CustomTypeOp::new(
+                            |ocx| {
+                                match deeply_normalize(
+                                    ocx.infcx.at(
+                                        &ObligationCause::dummy_with_span(self.span),
+                                        param_env,
+                                    ),
+                                    t1,
+                                ) {
+                                    Ok(normalized_ty) => {
+                                        t1 = normalized_ty;
+                                    }
+                                    Err(e) => {
+                                        infcx.err_ctxt().report_fulfillment_errors(e);
+                                    }
+                                }
 
-                TypeOutlives::new(
-                    &mut *self,
-                    tcx,
-                    region_bound_pairs,
-                    Some(implicit_region_bound),
-                    known_type_outlives_obligations,
-                )
-                .type_must_outlive(origin, t1, r2, constraint_category);
-            }
+                                Ok(())
+                            },
+                            "normalize type outlives obligation",
+                        )
+                        .fully_perform(infcx, self.span);
+
+                        match result {
+                            Ok(TypeOpOutput { output: (), constraints, .. }) => {
+                                if let Some(constraints) = constraints {
+                                    assert!(
+                                        constraints.member_constraints.is_empty(),
+                                        "FIXME(-Znext-solver): How do I handle these?"
+                                    );
+                                    outlives_predicates
+                                        .extend(constraints.outlives.iter().copied());
+                                }
+                            }
+                            Err(_) => {}
+                        }
+                    }
 
-            GenericArgKind::Const(_) => unreachable!(),
+                    // 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!(),
+            }
         }
     }
 

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_with_skipped_universes;
+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 +222,35 @@ 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(outlives) = bound.as_type_outlives_clause() else { continue };
+            let ty::OutlivesPredicate(mut ty, region) = outlives.skip_binder();
+
+            // In the new solver, normalize the type-outlives obligation assumptions.
+            if self.infcx.next_trait_solver() {
+                match deeply_normalize_with_skipped_universes(
+                    self.infcx.at(&ObligationCause::misc(span, defining_ty_def_id), self.param_env),
+                    ty,
+                    vec![None; ty.outer_exclusive_binder().as_usize()],
+                ) {
+                    Ok(normalized_ty) => {
+                        ty = normalized_ty;
+                    }
+                    Err(e) => {
+                        self.infcx.err_ctxt().report_fulfillment_errors(e);
+                    }
+                }
+            }
+
+            known_type_outlives_obligations
+                .push(outlives.rebind(ty::OutlivesPredicate(ty, region)));
+        }
+        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 +268,6 @@ 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 +332,19 @@ 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 +353,12 @@ 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/outlives/obligations.rs

@@ -153,22 +153,28 @@ impl<'tcx> InferCtxt<'tcx> {
             .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, origin.clone()).map_err(|e| (e, origin.clone()))?;
-            debug!(?sup_type, ?sub_region, ?origin);
-
-            let outlives = &mut TypeOutlives::new(
-                self,
-                self.tcx,
-                outlives_env.region_bound_pairs(),
-                None,
-                &normalized_caller_bounds,
-            );
-            let category = origin.to_constraint_category();
-            outlives.type_must_outlive(origin, sup_type, sub_region, category);
+        // Must loop since the process of normalizing may itself register region obligations.
+        loop {
+            let my_region_obligations = self.take_registered_region_obligations();
+            if my_region_obligations.is_empty() {
+                break;
+            }
+
+            for RegionObligation { sup_type, sub_region, origin } in my_region_obligations {
+                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(
+                    self,
+                    self.tcx,
+                    outlives_env.region_bound_pairs(),
+                    None,
+                    &normalized_caller_bounds,
+                );
+                let category = origin.to_constraint_category();
+                outlives.type_must_outlive(origin, sup_type, sub_region, category);
+            }
         }
 
         Ok(())

compiler/rustc_trait_selection/src/regions.rs

@@ -24,12 +24,13 @@ impl<'tcx> InferCtxtRegionExt<'tcx> for InferCtxt<'tcx> {
             let ty = self.resolve_vars_if_possible(ty);
 
             if self.next_trait_solver() {
-                crate::solve::deeply_normalize(
+                crate::solve::deeply_normalize_with_skipped_universes(
                     self.at(
                         &ObligationCause::dummy_with_span(origin.span()),
                         outlives_env.param_env,
                     ),
                     ty,
+                    vec![None; ty.outer_exclusive_binder().as_usize()],
                 )
                 .map_err(|_| ty)
             } else {

tests/ui/traits/next-solver/normalize-region-obligations.rs

@@ -1,4 +1,4 @@
-// revisions: normalize_param_env normalize_obligation
+// revisions: normalize_param_env normalize_obligation hrtb
 // check-pass
 // compile-flags: -Znext-solver
 
@@ -7,16 +7,23 @@ trait Foo {
     type Gat<'a> where <Self as Mirror>::Assoc: 'a;
     #[cfg(normalize_obligation)]
     type Gat<'a> where Self: 'a;
+    #[cfg(hrtb)]
+    type Gat<'b> where for<'a> <Self as MirrorRegion<'a>>::Assoc: 'b;
 }
 
 trait Mirror { type Assoc: ?Sized; }
 impl<T: ?Sized> Mirror for T { type Assoc = T; }
 
+trait MirrorRegion<'a> { type Assoc: ?Sized; }
+impl<'a, T> MirrorRegion<'a> for T { type Assoc = T; }
+
 impl<T> Foo for T {
     #[cfg(normalize_param_env)]
     type Gat<'a> = i32 where T: 'a;
     #[cfg(normalize_obligation)]
     type Gat<'a> = i32 where <T as Mirror>::Assoc: 'a;
+    #[cfg(hrtb)]
+    type Gat<'b> = i32 where Self: 'b;
 }
 
 fn main() {}