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librustc: Add NonZero lang item and use it if possible for nullable pointer enum opt.

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This commit is contained in:
Luqman Aden 2014-12-04 16:56:57 -05:00
parent 6d91419f27
commit 46e7376489
2 changed files with 15 additions and 1 deletions
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2
src/librustc/middle/lang_items.rs
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@ -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;

14
src/librustc_trans/trans/adt.rs
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@ -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);