B.foo "hello" : String × String
[Meta.synthInstance] preprocess: Add String ==> Add String
  [Meta.synthInstance] 
    [Meta.synthInstance] main goal Add String
    [Meta.synthInstance.newSubgoal] Add String
    [Meta.synthInstance.globalInstances] Add String, []
    [Meta.synthInstance] failed
[Meta.synthInstance] preprocess: Add Bool ==> Add Bool
  [Meta.synthInstance] 
    [Meta.synthInstance] main goal Add Bool
    [Meta.synthInstance.newSubgoal] Add Bool
    [Meta.synthInstance.globalInstances] Add Bool, []
    [Meta.synthInstance] failed