error: unconstrained generic constant
  --> $DIR/needs_where_clause.rs:11:6
   |
LL |   b: [f32; complex_maths::<T>(N)],
   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
help: try adding a `where` bound
   |
LL | struct Example<T, const N: usize> where [(); complex_maths::<T>(N)]: {
   |                                   ++++++++++++++++++++++++++++++++++

error: aborting due to 1 previous error