---

yaml
---
r: 166764
b: refs/heads/master
c: 46e7376
h: refs/heads/master
v: v3

Author: luqmana

[refs]

@@ -1,5 +1,5 @@
 ---
-refs/heads/master: 6d91419f27b25810f2cfcd263e0e20b62910f4ff
+refs/heads/master: 46e73764896316ef1384591656cfca01280c5e5c
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
 refs/heads/snap-stage3: 023dfb0c898d851dee6ace2f8339b73b5287136b
 refs/heads/try: f5d619caf9f32458680fae55526b99582ca682dd

trunk/src/librustc/middle/lang_items.rs

@@ -327,6 +327,8 @@ lets_do_this! {
     NoSyncItem,                      "no_sync_bound",           no_sync_bound;
     ManagedItem,                     "managed_bound",           managed_bound;
 
+    NonZeroItem,                     "non_zero",                non_zero;
+
     IteratorItem,                    "iterator",                iterator;
 
     StackExhaustedLangItem,          "stack_exhausted",         stack_exhausted;

trunk/src/librustc_trans/trans/adt.rs

@@ -357,7 +357,19 @@ fn find_discr_field_candidate<'tcx>(tcx: &ty::ctxt<'tcx>, ty: Ty<'tcx>) -> Optio
         // Closures are a pair of pointers: the code and environment
         ty::ty_closure(..) => Some(vec![FAT_PTR_ADDR]),
 
-        // Perhaps one of the fields of this struct is non-null
+        // Is this the NonZero lang item wrapping a pointer or integer type?
+        ty::ty_struct(did, ref substs) if Some(did) == tcx.lang_items.non_zero() => {
+            let nonzero_fields = ty::lookup_struct_fields(tcx, did);
+            assert_eq!(nonzero_fields.len(), 1);
+            let nonzero_field = ty::lookup_field_type(tcx, did, nonzero_fields[0].id, substs);
+            match nonzero_field.sty {
+                ty::ty_ptr(..) | ty::ty_int(..) |
+                ty::ty_uint(..) => Some(vec![0]),
+                _ => None
+            }
+        },
+
+        // Perhaps one of the fields of this struct is non-zero
         // let's recurse and find out
         ty::ty_struct(def_id, ref substs) => {
             let fields = ty::lookup_struct_fields(tcx, def_id);