Type error:
project/simple/bmod.sail:3.18-23:
3 |function main() = hello()
  |                  ^---^
  | Not in scope
  | 
  | Try requiring module A to bring the following into scope for module B:
  | project/simple/amod.sail:5.4-9:
  | 5 |val hello : unit -> unit
  |   |    ^---^ definition here in A
  | project/fail_simple.sail_project:6.0-1:
  | 6 |B {
  |   |^ add 'requires A' within B here