arr! with no type loops infinitely in the compiler #30

rustc 1.15.0-nightly (daf8c1dfc 2016-12-05)
error: recursion limit reached while expanding the macro `arr`
 --> <anon>:5:24
  |
5 |     ($($x:expr,)*) => (arr![$($x),*])
  |                        ^^^^^^^^^^^^^
...
9 |     arr![]
  |     ------ in this macro invocation