fix modes on dtors

src/libsyntax/ast_util.rs

@@ -399,7 +399,7 @@ fn operator_prec(op: ast::binop) -> uint {
 fn dtor_dec() -> fn_decl {
     let nil_t = @{id: 0, node: ty_nil, span: dummy_sp()};
     // dtor has one argument, of type ()
-    {inputs: ~[{mode: ast::expl(ast::by_ref),
+    {inputs: ~[{mode: ast::infer(0), // tjc: node id???
                 ty: nil_t, ident: parse::token::special_idents::underscore,
                 id: 0}],
      output: nil_t, cf: return_val}

src/test/run-pass/dtor-explicit-mode.rs

@@ -0,0 +1,6 @@
+struct Foo {
+    x: int,
+    drop { }
+}
+
+fn main() {}