Metadata decoding of more than one attribute like mutable and non_owned broken

[bill-myers]

It seems the decoding of [mutable] and [non_owned] is broken: specifically it seems they are ignored when applied on a struct in an external module, when another attribute follows.

In particular, it seems that when more than one attribute is present, only the last attribute survives encode+decode, and the others are somehow lost.

extern mod std;
use core::cell::Cell;
use std::rc::RcMut;
use std::arc::RWARC;

fn check_const<T: Const>(v: &T)
{
}

fn check_owned<T: Owned>(v: &T)
{
}

#[mutable]
#[deriving(Clone)]
pub struct MyCell<T> {
    priv value: Option<T>
}


fn test(c: &Cell<u32>, m: &RcMut<u32>, a: &RWARC<u32>, mc: &MyCell<u32>)
{
    // these succeed but should fail
    check_const(c);
    check_owned(m);

    // these fail as expected
    check_const(m);
    check_const(a);
    check_const(mc);
}

[thestinger]

Nominating for the production ready milestone.

[bill-myers]

Should be fixable with the following patch:

diff --git a/src/librustc/middle/ty.rs b/src/librustc/middle/ty.rs
index c51fba8..8b1100a 100644
--- a/src/librustc/middle/ty.rs
+++ b/src/librustc/middle/ty.rs
@@ -4179,7 +4179,7 @@ pub fn has_attr(tcx: ctxt, did: def_id, attr: &str) -> bool {
     } else {
         let mut ret = false;
         do csearch::get_item_attrs(tcx.cstore, did) |meta_items| {
-            ret = attr::contains_name(meta_items, attr);
+            ret = ret || attr::contains_name(meta_items, attr);
         }
         ret
     }

[Aatch]

Fixed by #7018.