comments

3 files changed, 31 insertions, 23 deletions

diff --git a/src/librustc/infer/outlives/obligations.rs b/src/librustc/infer/outlives/obligations.rs
index 221d378d621..3c3aba372fb 100644
--- a/src/librustc/infer/outlives/obligations.rs
+++ b/src/librustc/infer/outlives/obligations.rs
@@ -181,18 +181,6 @@ impl<'cx, 'gcx, 'tcx> InferCtxt<'cx, 'gcx, 'tcx> {
             TypeOutlives::new(self, region_bound_pairs, implicit_region_bound, param_env);
         outlives.type_must_outlive(origin, ty, region);
     }
-
-    /// Ignore the region obligations, not bothering to prove
-    /// them. This function should not really exist; it is used to
-    /// accommodate some older code for the time being.
-    pub fn ignore_region_obligations(&self) {
-        assert!(
-            !self.in_snapshot.get(),
-            "cannot ignore registered region obligations in a snapshot"
-        );
-
-        self.region_obligations.borrow_mut().clear();
-    }
 }
 
 #[must_use] // you ought to invoke `into_accrued_obligations` when you are done =)
diff --git a/src/librustc/traits/mod.rs b/src/librustc/traits/mod.rs
index 55bd10e9225..a3a5c26ec18 100644
--- a/src/librustc/traits/mod.rs
+++ b/src/librustc/traits/mod.rs
@@ -431,6 +431,9 @@ pub fn type_known_to_meet_bound<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx
         // this function's result remains infallible, we must confirm
         // that guess. While imperfect, I believe this is sound.
 
+        // The handling of regions in this area of the code is terrible,
+        // see issue #29149. We should be able to improve on this with
+        // NLL.
         let mut fulfill_cx = FulfillmentContext::new_ignoring_regions();
 
         // We can use a dummy node-id here because we won't pay any mind
@@ -511,8 +514,24 @@ pub fn normalize_param_env_or_error<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                            unnormalized_env.reveal);
 
     tcx.infer_ctxt().enter(|infcx| {
-        let predicates = match fully_normalize(
+        // FIXME. We should really... do something with these region
+        // obligations. But this call just continues the older
+        // behavior (i.e., doesn't cause any new bugs), and it would
+        // take some further refactoring to actually solve them. In
+        // particular, we would have to handle implied bounds
+        // properly, and that code is currently largely confined to
+        // regionck (though I made some efforts to extract it
+        // out). -nmatsakis
+        //
+        // @arielby: In any case, these obligations are checked
+        // by wfcheck anyway, so I'm not sure we have to check
+        // them here too, and we will remove this function when
+        // we move over to lazy normalization *anyway*.
+        let fulfill_cx = FulfillmentContext::new_ignoring_regions();
+
+        let predicates = match fully_normalize_with_fulfillcx(
             &infcx,
+            fulfill_cx,
             cause,
             elaborated_env,
             // You would really want to pass infcx.param_env.caller_bounds here,
@@ -537,16 +556,6 @@ pub fn normalize_param_env_or_error<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         let region_scope_tree = region::ScopeTree::default();
         let free_regions = FreeRegionMap::new();
 
-        // FIXME. We should really... do something with these region
-        // obligations. But this call just continues the older
-        // behavior (i.e., doesn't cause any new bugs), and it would
-        // take some further refactoring to actually solve them. In
-        // particular, we would have to handle implied bounds
-        // properly, and that code is currently largely confined to
-        // regionck (though I made some efforts to extract it
-        // out). -nmatsakis
-        let _ = infcx.ignore_region_obligations();
-
         infcx.resolve_regions_and_report_errors(region_context, &region_scope_tree, &free_regions);
         let predicates = match infcx.fully_resolve(&predicates) {
             Ok(predicates) => predicates,
diff --git a/src/librustc/traits/specialize/mod.rs b/src/librustc/traits/specialize/mod.rs
index f83e131c327..1b5b0d35ba3 100644
--- a/src/librustc/traits/specialize/mod.rs
+++ b/src/librustc/traits/specialize/mod.rs
@@ -241,6 +241,17 @@ fn fulfill_implication<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
     // (which are packed up in penv)
 
     infcx.save_and_restore_in_snapshot_flag(|infcx| {
+        // If we came from `translate_substs`, we already know that the
+        // predicates for our impl hold (after all, we know that a more
+        // specialized impl holds, so our impl must hold too), and
+        // we only want to process the projections to determine the
+        // the types in our substs using RFC 447, so we can safely
+        // ignore region obligations, which allows us to avoid threading
+        // a node-id to assign them with.
+        //
+        // If we came from specialization graph construction, then
+        // we already make a mockery out of the region system, so
+        // why not ignore them a bit earlier?
         let mut fulfill_cx = FulfillmentContext::new_ignoring_regions();
         for oblig in obligations.into_iter() {
             fulfill_cx.register_predicate_obligation(&infcx, oblig);