From 4835764592414d881af35b66049ab493a8037735 Mon Sep 17 00:00:00 2001
From: Inokentiy Babushkin <twk@twki.de>
Date: Thu, 31 Aug 2017 23:51:41 +0200
Subject: [PATCH] Fixed issue #28.

Trait objects weren't translated correctly in some edge cases. Combined
with an ordering bug in the filtering logic, this led to crashes when
sentinel values were passed to the analysis mechanisms.
---
 src/semcheck/translate.rs | 33 ++++++++++++++++++++++-----------
 tests/examples.rs         |  1 +
 2 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/src/semcheck/translate.rs b/src/semcheck/translate.rs
index 4426bfcc9a61f..b5ef029541997 100644
--- a/src/semcheck/translate.rs
+++ b/src/semcheck/translate.rs
@@ -174,21 +174,31 @@ impl<'a, 'gcx, 'tcx> TranslationContext<'a, 'gcx, 'tcx> {
                 TyDynamic(preds, region) => {
                     // hacky error catching mechanism
                     use rustc::hir::def_id::{CRATE_DEF_INDEX, DefId};
-                    let mut success = true;
+                    use std::cell::Cell;
+
+                    let success = Cell::new(true);
                     let err_pred = AutoTrait(DefId::local(CRATE_DEF_INDEX));
 
-                    let target_preds = self.tcx.mk_existential_predicates(preds.iter().map(|p| {
+                    let res: Vec<_> = preds.iter().map(|p| {
+                        debug!("pred: {:?}", p);
                         match *p.skip_binder() {
-                            Trait(ExistentialTraitRef { def_id: did, substs }) => {
+                            Trait(existential_trait_ref) => {
+                                let trait_ref = Binder(existential_trait_ref)
+                                    .with_self_ty(self.tcx, self.tcx.types.err);
+                                let did = trait_ref.skip_binder().def_id;
+                                let substs = trait_ref.skip_binder().substs;
+
                                 if let Some((target_def_id, target_substs)) =
                                     self.translate_orig_substs(index_map, did, substs)
                                 {
-                                    Trait(ExistentialTraitRef {
+                                    let target_trait_ref = TraitRef {
                                         def_id: target_def_id,
-                                        substs: target_substs
-                                    })
-                                } else {
-                                    success = false;
+                                        substs: target_substs,
+                                    };
+                                    Trait(ExistentialTraitRef::erase_self_ty(self.tcx,
+                                                                             target_trait_ref))
+                                } else  {
+                                    success.set(false);
                                     err_pred
                                 }
                             },
@@ -202,7 +212,7 @@ impl<'a, 'gcx, 'tcx> TranslationContext<'a, 'gcx, 'tcx> {
                                         ty: ty,
                                     })
                                 } else {
-                                    success = false;
+                                    success.set(false);
                                     err_pred
                                 }
                             },
@@ -210,9 +220,10 @@ impl<'a, 'gcx, 'tcx> TranslationContext<'a, 'gcx, 'tcx> {
                                 AutoTrait(self.translate_orig(did))
                             },
                         }
-                    }));
+                    }).collect();
 
-                    if success {
+                    if success.get() {
+                        let target_preds = self.tcx.mk_existential_predicates(res.iter());
                         self.tcx.mk_dynamic(Binder(target_preds), region)
                     } else {
                         ty
diff --git a/tests/examples.rs b/tests/examples.rs
index 2ac9fde110660..1705fc1341fc4 100644
--- a/tests/examples.rs
+++ b/tests/examples.rs
@@ -121,4 +121,5 @@ test!(structs);
 test!(swap);
 test!(traits);
 test!(trait_impls);
+test!(trait_objects);
 test!(ty_alias);