target set!: (name: String) to: v :=
  if: (target has-slot?: name)
    then: {
      target set-slot: name to: v
      v
    }
    else: {
      { done |
        target delegates map: { d |
          { d set!: name to: v
            done yield: v
          } handle: {
            @(undefined: _) -> @ok
          }
        }

        error: @(undefined: name)
      } call/cc
    }

macro ((name: Dispatch) set!: v)
  { msg = `Dispatch new: name particle to: ['this]
    `(~(name target) set!: ~(msg name) to: ~v)
  } call