remove keys w/ skolemized regions from proj cache when popping skolemized regions

src/librustc/infer/higher_ranked/mod.rs

@@ -839,5 +839,9 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         debug!("pop_skolemized({:?})", skol_map);
         let skol_regions: FnvHashSet<_> = skol_map.values().cloned().collect();
         self.region_vars.pop_skolemized(&skol_regions, &snapshot.region_vars_snapshot);
+        if !skol_map.is_empty() {
+            self.projection_cache.borrow_mut().rollback_skolemized(
+                &snapshot.projection_cache_snapshot);
+        }
     }
 }

src/librustc/traits/project.rs

@@ -167,7 +167,7 @@ pub fn poly_project_and_unify_type<'cx, 'gcx, 'tcx>(
             infcx.skolemize_late_bound_regions(&obligation.predicate, snapshot);
 
         let skol_obligation = obligation.with(skol_predicate);
-        match project_and_unify_type(selcx, &skol_obligation) {
+        let r = match project_and_unify_type(selcx, &skol_obligation) {
             Ok(result) => {
                 let span = obligation.cause.span;
                 match infcx.leak_check(false, span, &skol_map, snapshot) {
@@ -178,7 +178,9 @@ pub fn poly_project_and_unify_type<'cx, 'gcx, 'tcx>(
             Err(e) => {
                 Err(e)
             }
-        }
+        };
+
+        r
     })
 }
 
@@ -1396,6 +1398,10 @@ impl<'tcx> ProjectionCache<'tcx> {
         self.map.rollback_to(snapshot.snapshot);
     }
 
+    pub fn rollback_skolemized(&mut self, snapshot: &ProjectionCacheSnapshot) {
+        self.map.partial_rollback(&snapshot.snapshot, &|k| k.has_re_skol());
+    }
+
     pub fn commit(&mut self, snapshot: ProjectionCacheSnapshot) {
         self.map.commit(snapshot.snapshot);
     }

src/librustc/ty/flags.rs

@@ -11,6 +11,7 @@
 use ty::subst::Substs;
 use ty::{self, Ty, TypeFlags, TypeFoldable};
 
+#[derive(Debug)]
 pub struct FlagComputation {
     pub flags: TypeFlags,
 
@@ -182,24 +183,9 @@ impl FlagComputation {
     }
 
     fn add_region(&mut self, r: &ty::Region) {
-        match *r {
-            ty::ReVar(..) => {
-                self.add_flags(TypeFlags::HAS_RE_INFER);
-                self.add_flags(TypeFlags::KEEP_IN_LOCAL_TCX);
-            }
-            ty::ReSkolemized(..) => {
-                self.add_flags(TypeFlags::HAS_RE_INFER);
-                self.add_flags(TypeFlags::HAS_RE_SKOL);
-                self.add_flags(TypeFlags::KEEP_IN_LOCAL_TCX);
-            }
-            ty::ReLateBound(debruijn, _) => { self.add_depth(debruijn.depth); }
-            ty::ReEarlyBound(..) => { self.add_flags(TypeFlags::HAS_RE_EARLY_BOUND); }
-            ty::ReStatic | ty::ReErased => {}
-            _ => { self.add_flags(TypeFlags::HAS_FREE_REGIONS); }
-        }
-
-        if !r.is_global() {
-            self.add_flags(TypeFlags::HAS_LOCAL_NAMES);
+        self.add_flags(r.type_flags());
+        if let ty::ReLateBound(debruijn, _) = *r {
+            self.add_depth(debruijn.depth);
         }
     }
 

src/librustc/ty/fold.rs

@@ -91,6 +91,9 @@ pub trait TypeFoldable<'tcx>: fmt::Debug + Clone {
     fn needs_subst(&self) -> bool {
         self.has_type_flags(TypeFlags::NEEDS_SUBST)
     }
+    fn has_re_skol(&self) -> bool {
+        self.has_type_flags(TypeFlags::HAS_RE_SKOL)
+    }
     fn has_closure_types(&self) -> bool {
         self.has_type_flags(TypeFlags::HAS_TY_CLOSURE)
     }
@@ -632,26 +635,15 @@ struct HasTypeFlagsVisitor {
 
 impl<'tcx> TypeVisitor<'tcx> for HasTypeFlagsVisitor {
     fn visit_ty(&mut self, t: Ty) -> bool {
-        t.flags.get().intersects(self.flags)
+        let flags = t.flags.get();
+        debug!("HasTypeFlagsVisitor: t={:?} t.flags={:?} self.flags={:?}", t, flags, self.flags);
+        flags.intersects(self.flags)
     }
 
     fn visit_region(&mut self, r: &'tcx ty::Region) -> bool {
-        if self.flags.intersects(ty::TypeFlags::HAS_LOCAL_NAMES) {
-            // does this represent a region that cannot be named
-            // in a global way? used in fulfillment caching.
-            match *r {
-                ty::ReStatic | ty::ReEmpty | ty::ReErased => {}
-                _ => return true,
-            }
-        }
-        if self.flags.intersects(ty::TypeFlags::HAS_RE_INFER |
-                                 ty::TypeFlags::KEEP_IN_LOCAL_TCX) {
-            match *r {
-                ty::ReVar(_) | ty::ReSkolemized(..) => { return true }
-                _ => {}
-            }
-        }
-        false
+        let flags = r.type_flags();
+        debug!("HasTypeFlagsVisitor: r={:?} r.flags={:?} self.flags={:?}", r, flags, self.flags);
+        flags.intersects(self.flags)
     }
 }
 

src/librustc/ty/mod.rs

@@ -477,6 +477,7 @@ bitflags! {
                                   TypeFlags::HAS_SELF.bits |
                                   TypeFlags::HAS_TY_INFER.bits |
                                   TypeFlags::HAS_RE_INFER.bits |
+                                  TypeFlags::HAS_RE_SKOL.bits |
                                   TypeFlags::HAS_RE_EARLY_BOUND.bits |
                                   TypeFlags::HAS_FREE_REGIONS.bits |
                                   TypeFlags::HAS_TY_ERR.bits |

src/librustc/ty/sty.rs

@@ -406,7 +406,7 @@ impl<T> Binder<T> {
 
 impl fmt::Debug for TypeFlags {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{}", self.bits)
+        write!(f, "{:x}", self.bits)
     }
 }
 
@@ -866,6 +866,35 @@ impl Region {
             r => r
         }
     }
+
+    pub fn type_flags(&self) -> TypeFlags {
+        let mut flags = TypeFlags::empty();
+
+        match *self {
+            ty::ReVar(..) => {
+                flags = flags | TypeFlags::HAS_RE_INFER;
+                flags = flags | TypeFlags::KEEP_IN_LOCAL_TCX;
+            }
+            ty::ReSkolemized(..) => {
+                flags = flags | TypeFlags::HAS_RE_INFER;
+                flags = flags | TypeFlags::HAS_RE_SKOL;
+                flags = flags | TypeFlags::KEEP_IN_LOCAL_TCX;
+            }
+            ty::ReLateBound(..) => { }
+            ty::ReEarlyBound(..) => { flags = flags | TypeFlags::HAS_RE_EARLY_BOUND; }
+            ty::ReStatic | ty::ReErased => { }
+            _ => { flags = flags | TypeFlags::HAS_FREE_REGIONS; }
+        }
+
+        match *self {
+            ty::ReStatic | ty::ReEmpty | ty::ReErased => (),
+            _ => flags = flags | TypeFlags::HAS_LOCAL_NAMES,
+        }
+
+        debug!("type_flags({:?}) = {:?}", self, flags);
+
+        flags
+    }
 }
 
 // Type utilities

src/librustc_data_structures/snapshot_map/mod.rs

@@ -11,6 +11,7 @@
 use fnv::FnvHashMap;
 use std::hash::Hash;
 use std::ops;
+use std::mem;
 
 #[cfg(test)]
 mod test;
@@ -31,6 +32,7 @@ enum UndoLog<K, V> {
     CommittedSnapshot,
     Inserted(K),
     Overwrite(K, V),
+    Noop,
 }
 
 impl<K, V> SnapshotMap<K, V>
@@ -100,24 +102,33 @@ impl<K, V> SnapshotMap<K, V>
         }
     }
 
+    pub fn partial_rollback<F>(&mut self,
+                               snapshot: &Snapshot,
+                               should_revert_key: &F)
+        where F: Fn(&K) -> bool
+    {
+        self.assert_open_snapshot(snapshot);
+        for i in (snapshot.len + 1..self.undo_log.len()).rev() {
+            let reverse = match self.undo_log[i] {
+                UndoLog::OpenSnapshot => false,
+                UndoLog::CommittedSnapshot => false,
+                UndoLog::Noop => false,
+                UndoLog::Inserted(ref k) => should_revert_key(k),
+                UndoLog::Overwrite(ref k, _) => should_revert_key(k),
+            };
+
+            if reverse {
+                let entry = mem::replace(&mut self.undo_log[i], UndoLog::Noop);
+                self.reverse(entry);
+            }
+        }
+    }
+
     pub fn rollback_to(&mut self, snapshot: Snapshot) {
         self.assert_open_snapshot(&snapshot);
         while self.undo_log.len() > snapshot.len + 1 {
-            match self.undo_log.pop().unwrap() {
-                UndoLog::OpenSnapshot => {
-                    panic!("cannot rollback an uncommitted snapshot");
-                }
-
-                UndoLog::CommittedSnapshot => {}
-
-                UndoLog::Inserted(key) => {
-                    self.map.remove(&key);
-                }
-
-                UndoLog::Overwrite(key, old_value) => {
-                    self.map.insert(key, old_value);
-                }
-            }
+            let entry = self.undo_log.pop().unwrap();
+            self.reverse(entry);
         }
 
         let v = self.undo_log.pop().unwrap();
@@ -127,6 +138,26 @@ impl<K, V> SnapshotMap<K, V>
         });
         assert!(self.undo_log.len() == snapshot.len);
     }
+
+    fn reverse(&mut self, entry: UndoLog<K, V>) {
+        match entry {
+            UndoLog::OpenSnapshot => {
+                panic!("cannot rollback an uncommitted snapshot");
+            }
+
+            UndoLog::CommittedSnapshot => {}
+
+            UndoLog::Inserted(key) => {
+                self.map.remove(&key);
+            }
+
+            UndoLog::Overwrite(key, old_value) => {
+                self.map.insert(key, old_value);
+            }
+
+            UndoLog::Noop => {}
+        }
+    }
 }
 
 impl<'k, K, V> ops::Index<&'k K> for SnapshotMap<K, V>

src/test/run-pass/project-cache-issue-37154.rs

@@ -0,0 +1,28 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Regression test for #37154: the problem here was that the cache
+// results in a false error because it was caching skolemized results
+// even after those skolemized regions had been popped.
+
+trait Foo {
+    fn method(&self) {}
+}
+
+struct Wrapper<T>(T);
+
+impl<T> Foo for Wrapper<T> where for<'a> &'a T: IntoIterator<Item=&'a ()> {}
+
+fn f(x: Wrapper<Vec<()>>) {
+    x.method(); // This works.
+    x.method(); // error: no method named `method`
+}
+
+fn main() { }