mapper.createMap(User, UserDto).forMember(
  (d) => d.someArrayField,
  mapWith(
    () => XDto,
    (s) => [], // the mapper will return an XDto instance instead of this value
    () => X
  )
)

class A {
  // ...
  @AutoMap(() => B)
  b: B[]
}

class B {
  // ...
  @AutoMap(() => C)
  c: C
}

class C {}

class AVm {
  @AutoMap(() => CVm)
  c: CVm[] // I want to extract this from B[]
}

class CVm {}