tests/fail-fl-num-inval-len.nt

   1 { 23 : 17 }
   2 ---
   3 1:8 - Expecting a fixed length (multiple of eight bits), `uleb128`, `sleb128`, or `s:` followed with a valid encoding (`u8`, `u16be`, `u16le`, `u32be`, `u32le`, or `latin1` to `latin10`)