Auto merge of #55305 - nikomatsakis:universes-refactor-3, r=scalexm

universes refactor 3

Some more refactorings from my universe branch. These are getting a bit more "invasive" -- they start to plumb the universe information through the canonicalization process. As of yet though I don't **believe** this branch changes our behavior in any notable way, though I'm marking the branch as `WIP` to give myself a chance to verify this.

r? @scalexm

3 files changed, 10 insertions, 14 deletions

diff --git a/src/librustc/ty/error.rs b/src/librustc/ty/error.rs
index ed6e372fe76..855983042c0 100644
--- a/src/librustc/ty/error.rs
+++ b/src/librustc/ty/error.rs
@@ -53,8 +53,6 @@ pub enum TypeError<'tcx> {
     ProjectionMismatched(ExpectedFound<DefId>),
     ProjectionBoundsLength(ExpectedFound<usize>),
     ExistentialMismatch(ExpectedFound<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>),
-
-    OldStyleLUB(Box<TypeError<'tcx>>),
 }
 
 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Debug, Copy)]
@@ -166,9 +164,6 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
                 report_maybe_different(f, &format!("trait `{}`", values.expected),
                                        &format!("trait `{}`", values.found))
             }
-            OldStyleLUB(ref err) => {
-                write!(f, "{}", err)
-            }
         }
     }
 }
@@ -266,12 +261,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                     }
                 }
             },
-            OldStyleLUB(err) => {
-                db.note("this was previously accepted by the compiler but has been phased out");
-                db.note("for more information, see https://github.com/rust-lang/rust/issues/45852");
-
-                self.note_and_explain_type_err(db, &err, sp);
-            }
             CyclicTy(ty) => {
                 // Watch out for various cases of cyclic types and try to explain.
                 if ty.is_closure() || ty.is_generator() {
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index f8fc2cc8303..ad26383df6a 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -1522,10 +1522,17 @@ impl UniverseIndex {
 
     /// True if `self` can name a name from `other` -- in other words,
     /// if the set of names in `self` is a superset of those in
-    /// `other`.
+    /// `other` (`self >= other`).
     pub fn can_name(self, other: UniverseIndex) -> bool {
         self.private >= other.private
     }
+
+    /// True if `self` cannot name some names from `other` -- in other
+    /// words, if the set of names in `self` is a strict subset of
+    /// those in `other` (`self < other`).
+    pub fn cannot_name(self, other: UniverseIndex) -> bool {
+        self.private < other.private
+    }
 }
 
 /// The "placeholder index" fully defines a placeholder region.
@@ -1540,6 +1547,8 @@ pub struct Placeholder {
     pub name: BoundRegion,
 }
 
+impl_stable_hash_for!(struct Placeholder { universe, name });
+
 /// When type checking, we use the `ParamEnv` to track
 /// details about the set of where-clauses that are in scope at this
 /// particular point.
diff --git a/src/librustc/ty/structural_impls.rs b/src/librustc/ty/structural_impls.rs
index ba5b714a0e7..05f5f923557 100644
--- a/src/librustc/ty/structural_impls.rs
+++ b/src/librustc/ty/structural_impls.rs
@@ -455,7 +455,6 @@ impl<'a, 'tcx> Lift<'tcx> for ty::error::TypeError<'a> {
             ProjectionMismatched(x) => ProjectionMismatched(x),
             ProjectionBoundsLength(x) => ProjectionBoundsLength(x),
             Sorts(ref x) => return tcx.lift(x).map(Sorts),
-            OldStyleLUB(ref x) => return tcx.lift(x).map(OldStyleLUB),
             ExistentialMismatch(ref x) => return tcx.lift(x).map(ExistentialMismatch)
         })
     }
@@ -1003,7 +1002,6 @@ EnumTypeFoldableImpl! {
         (ty::error::TypeError::ProjectionBoundsLength)(x),
         (ty::error::TypeError::Sorts)(x),
         (ty::error::TypeError::ExistentialMismatch)(x),
-        (ty::error::TypeError::OldStyleLUB)(x),
     }
 }