could not initialize immutable in immutable by map

immutable.groovy

@groovy.transform.Immutable
class A {
  int x
}

@groovy.transform.Immutable
class B {
  int y
  @Delegate
  A a = new A([:])
}

println new B(x: 200)            // -> B(0, A(0))
println new B(y: 100)            // -> B(100, A(0))
println new B(y: 100, x: 200)    // -> B(100, A(0))

tuple-constructor.groovy

@groovy.transform.TupleConstructor
@groovy.transform.ToString
class A {
  int x
}

@groovy.transform.TupleConstructor
@groovy.transform.ToString
class B {
  int y
  @Delegate
  A a = new A()
}

println new B(x: 200)            // -> B(0, A(200))
println new B(y: 100)            // -> B(100, A(0))
println new B(y: 100, x: 200)    // -> B(100, A(200))