scala - how to call a subclass constructor with constrained access? -

i have below want compile

trait t{   def a: int }  class private(val a: int, a2: int) extends t{   def add(b: int): = new a(a + b, a2 + 2*b) }  object t{   def make(a: int): = {     new a(a, 2*a) // doesn't compile } 

here class has private constructor because want way construct a pass through constructor t.make or updated method a.add (which in example both garantie a2 = 2*a).

but because constructor private, cannot access parent trait t. same goes protected. basically, need inversed protected?

note: solution not satisfying lower (too much) restriction on constructor, maybe package-private. don't want other construction possible ones planned. lower constraint code in current file, don't know how either.

a few options.

• you can rename object t object a - have access a's private members

• you can make class a inner object t - can make constructor private[t], , t have access it.

• you can make package-private. mistaken when "lowering restriction much". package in scala doesn't have entire directory. doesn't need whole file. have complete control on content, , purpose of able trying here.