error: unconstrained generic constant
  --> $DIR/needs_where_clause.rs:11:6
   |
LL |   b: [f32; complex_maths::<T>(N)],
   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: try adding a `where` bound using this expression: `where [(); complex_maths::<T>(N)]:`

error: aborting due to previous error