error[E0080]: evaluation of constant value failed
 --> tests/compile/too_big.rs:1:1
  |
1 | / bit_struct::bit_struct! {
2 | |     struct TooMany(u16) {
3 | |         a: u32
4 | |     }
5 | | }
  | |_^ attempt to compute `16_usize - 32_usize`, which would overflow
  |
  = note: this error originates in the macro `$crate::impl_fields` which comes from the expansion of the macro `bit_struct::bit_struct` (in Nightly builds, run with -Z macro-backtrace for more info)