Merging upstream version 1.70.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

2 files changed, 26 insertions, 70 deletions

diff --git a/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs b/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs
index e413b2bb5..b8ba98fc0 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs
+++ b/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs
@@ -290,9 +290,9 @@ impl<'me, 'tcx> LeakCheck<'me, 'tcx> {
     ) -> TypeError<'tcx> {
         debug!("error: placeholder={:?}, other_region={:?}", placeholder, other_region);
         if self.overly_polymorphic {
-            TypeError::RegionsOverlyPolymorphic(placeholder.name, other_region)
+            TypeError::RegionsOverlyPolymorphic(placeholder.bound.kind, other_region)
         } else {
-            TypeError::RegionsInsufficientlyPolymorphic(placeholder.name, other_region)
+            TypeError::RegionsInsufficientlyPolymorphic(placeholder.bound.kind, other_region)
         }
     }
 }
@@ -424,9 +424,6 @@ impl<'tcx> MiniGraph<'tcx> {
                 &AddConstraint(Constraint::RegSubReg(a, b)) => {
                     each_edge(a, b);
                 }
-                &AddGiven(a, b) => {
-                    each_edge(a, tcx.mk_re_var(b));
-                }
                 &AddVerify(i) => span_bug!(
                     verifys[i].origin.span(),
                     "we never add verifications while doing higher-ranked things",
diff --git a/compiler/rustc_infer/src/infer/region_constraints/mod.rs b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
index 872f61747..7b272dfd2 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/mod.rs
+++ b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
@@ -7,7 +7,7 @@ use super::{
     InferCtxtUndoLogs, MiscVariable, RegionVariableOrigin, Rollback, Snapshot, SubregionOrigin,
 };
 
-use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
+use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::sync::Lrc;
 use rustc_data_structures::undo_log::UndoLogs;
@@ -104,26 +104,6 @@ pub struct RegionConstraintData<'tcx> {
     /// An example is a `A <= B` where neither `A` nor `B` are
     /// inference variables.
     pub verifys: Vec<Verify<'tcx>>,
-
-    /// A "given" is a relationship that is known to hold. In
-    /// particular, we often know from closure fn signatures that a
-    /// particular free region must be a subregion of a region
-    /// variable:
-    ///
-    ///    foo.iter().filter(<'a> |x: &'a &'b T| ...)
-    ///
-    /// In situations like this, `'b` is in fact a region variable
-    /// introduced by the call to `iter()`, and `'a` is a bound region
-    /// on the closure (as indicated by the `<'a>` prefix). If we are
-    /// naive, we wind up inferring that `'b` must be `'static`,
-    /// because we require that it be greater than `'a` and we do not
-    /// know what `'a` is precisely.
-    ///
-    /// This hashmap is used to avoid that naive scenario. Basically
-    /// we record the fact that `'a <= 'b` is implied by the fn
-    /// signature, and then ignore the constraint when solving
-    /// equations. This is a bit of a hack but seems to work.
-    pub givens: FxIndexSet<(Region<'tcx>, ty::RegionVid)>,
 }
 
 /// Represents a constraint that influences the inference process.
@@ -297,9 +277,6 @@ pub(crate) enum UndoLog<'tcx> {
     /// We added the given `verify`.
     AddVerify(usize),
 
-    /// We added the given `given`.
-    AddGiven(Region<'tcx>, ty::RegionVid),
-
     /// We added a GLB/LUB "combination variable".
     AddCombination(CombineMapType, TwoRegions<'tcx>),
 }
@@ -348,9 +325,6 @@ impl<'tcx> RegionConstraintStorage<'tcx> {
                 self.data.verifys.pop();
                 assert_eq!(self.data.verifys.len(), index);
             }
-            AddGiven(sub, sup) => {
-                self.data.givens.remove(&(sub, sup));
-            }
             AddCombination(Glb, ref regions) => {
                 self.glbs.remove(regions);
             }
@@ -420,7 +394,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
         // `RegionConstraintData` contains the relationship here.
         if *any_unifications {
             *any_unifications = false;
-            self.unification_table().reset_unifications(|_| UnifiedRegion(None));
+            self.unification_table_mut().reset_unifications(|_| UnifiedRegion::new(None));
         }
 
         data
@@ -447,7 +421,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
     ) -> RegionVid {
         let vid = self.var_infos.push(RegionVariableInfo { origin, universe });
 
-        let u_vid = self.unification_table().new_key(UnifiedRegion(None));
+        let u_vid = self.unification_table_mut().new_key(UnifiedRegion::new(None));
         assert_eq!(vid, u_vid.vid);
         self.undo_log.push(AddVar(vid));
         debug!("created new region variable {:?} in {:?} with origin {:?}", vid, universe, origin);
@@ -492,15 +466,6 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
         self.undo_log.push(AddVerify(index));
     }
 
-    pub(super) fn add_given(&mut self, sub: Region<'tcx>, sup: ty::RegionVid) {
-        // cannot add givens once regions are resolved
-        if self.data.givens.insert((sub, sup)) {
-            debug!("add_given({:?} <= {:?})", sub, sup);
-
-            self.undo_log.push(AddGiven(sub, sup));
-        }
-    }
-
     pub(super) fn make_eqregion(
         &mut self,
         origin: SubregionOrigin<'tcx>,
@@ -516,13 +481,13 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
             match (sub, sup) {
                 (Region(Interned(ReVar(sub), _)), Region(Interned(ReVar(sup), _))) => {
                     debug!("make_eqregion: unifying {:?} with {:?}", sub, sup);
-                    self.unification_table().union(*sub, *sup);
+                    self.unification_table_mut().union(*sub, *sup);
                     self.any_unifications = true;
                 }
                 (Region(Interned(ReVar(vid), _)), value)
                 | (value, Region(Interned(ReVar(vid), _))) => {
                     debug!("make_eqregion: unifying {:?} with {:?}", vid, value);
-                    self.unification_table().union_value(*vid, UnifiedRegion(Some(value)));
+                    self.unification_table_mut().union_value(*vid, UnifiedRegion::new(Some(value)));
                     self.any_unifications = true;
                 }
                 (_, _) => {}
@@ -633,28 +598,25 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
         }
     }
 
-    /// Resolves the passed RegionVid to the root RegionVid in the unification table
-    pub(super) fn opportunistic_resolve_var(&mut self, rid: ty::RegionVid) -> ty::RegionVid {
-        self.unification_table().find(rid).vid
-    }
-
-    /// If the Region is a `ReVar`, then resolves it either to the root value in
-    /// the unification table, if it exists, or to the root `ReVar` in the table.
-    /// If the Region is not a `ReVar`, just returns the Region itself.
-    pub fn opportunistic_resolve_region(
+    /// Resolves a region var to its value in the unification table, if it exists.
+    /// Otherwise, it is resolved to the root `ReVar` in the table.
+    pub fn opportunistic_resolve_var(
         &mut self,
         tcx: TyCtxt<'tcx>,
-        region: ty::Region<'tcx>,
+        vid: ty::RegionVid,
     ) -> ty::Region<'tcx> {
-        match *region {
-            ty::ReVar(rid) => {
-                let unified_region = self.unification_table().probe_value(rid);
-                unified_region.0.unwrap_or_else(|| {
-                    let root = self.unification_table().find(rid).vid;
-                    tcx.mk_re_var(root)
-                })
-            }
-            _ => region,
+        let mut ut = self.unification_table_mut(); // FIXME(rust-lang/ena#42): unnecessary mut
+        let root_vid = ut.find(vid).vid;
+        let resolved = ut
+            .probe_value(root_vid)
+            .get_value_ignoring_universes()
+            .unwrap_or_else(|| tcx.mk_re_var(root_vid));
+
+        // Don't resolve a variable to a region that it cannot name.
+        if self.var_universe(vid).can_name(self.universe(resolved)) {
+            resolved
+        } else {
+            tcx.mk_re_var(vid)
         }
     }
 
@@ -733,7 +695,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
     }
 
     #[inline]
-    fn unification_table(&mut self) -> super::UnificationTable<'_, 'tcx, RegionVidKey<'tcx>> {
+    fn unification_table_mut(&mut self) -> super::UnificationTable<'_, 'tcx, RegionVidKey<'tcx>> {
         ut::UnificationTable::with_log(&mut self.storage.unification_table, self.undo_log)
     }
 }
@@ -807,11 +769,8 @@ impl<'tcx> RegionConstraintData<'tcx> {
     /// Returns `true` if this region constraint data contains no constraints, and `false`
     /// otherwise.
     pub fn is_empty(&self) -> bool {
-        let RegionConstraintData { constraints, member_constraints, verifys, givens } = self;
-        constraints.is_empty()
-            && member_constraints.is_empty()
-            && verifys.is_empty()
-            && givens.is_empty()
+        let RegionConstraintData { constraints, member_constraints, verifys } = self;
+        constraints.is_empty() && member_constraints.is_empty() && verifys.is_empty()
     }
 }