  --> [ local path prefix ]/command/not_displayable.fpp:20:23
   |
20 |   async command C(a1: S)
   |                       ^ type of command parameter is not displayable
   |
  ::: [ local path prefix ]/command/not_displayable.fpp:10:6
   |
10 |   x: T
   |      - because this type is not displayable
   |
  ::: [ local path prefix ]/command/not_displayable.fpp:7:1
   |
 7 | type T
   | ------ type is defined here

