Add let destructuring for unique boxes

Issue #409

src/comp/middle/check_alt.rs

@@ -120,6 +120,7 @@ fn is_refutable(tcx: ty::ctxt, pat: @pat) -> bool {
       pat_wild. | pat_bind(_) { ret false; }
       pat_lit(_) { ret true; }
       pat_box(sub) { ret is_refutable(tcx, sub); }
+      pat_uniq(sub) { ret is_refutable(tcx, sub); }
       pat_rec(fields, _) {
         for field: field_pat in fields {
             if is_refutable(tcx, field.pat) { ret true; }

src/comp/middle/trans_alt.rs

@@ -656,6 +656,10 @@ fn bind_irrefutable_pat(bcx: @block_ctxt, pat: @ast::pat, val: ValueRef,
                         [C_int(0), C_int(back::abi::box_rc_field_body)]);
         bcx = bind_irrefutable_pat(bcx, inner, unboxed, table, true);
       }
+      ast::pat_uniq(inner) {
+        let val = Load(bcx, val);
+        bcx = bind_irrefutable_pat(bcx, inner, val, table, true);
+      }
       ast::pat_wild. | ast::pat_lit(_) { }
     }
     ret bcx;

src/test/run-pass/unique-destructure.rs

+fn main() {
+    let ~{a, b} = ~{a: 100, b: 200};
+    assert a + b == 300;
+}
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