error: expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found `expr` metavariable
  --> $DIR/nonterminal-expansion.rs:7:22
   |
LL |         #[repr(align($n))]
   |                      ^^
...
LL | pass_nonterminal!(n!());
   | ----------------------- in this macro invocation
   |
   = note: this error originates in the macro `pass_nonterminal` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 1 previous error