error[E0425]: cannot find value `b` in this scope
 --> tests/compile_failures/combine_inputs_missing.rs:5:18
  |
5 |     let result = combinebits!("aaaa aaaa bbbb bbbb");
  |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: a local variable with a similar name exists: `a`
  |
  = note: this error originates in the macro `combinebits` (in Nightly builds, run with -Z macro-backtrace for more info)