Type synonyms nested inside types do not always work

[vkuncak]

This crashes with mismatch between List[(Int,Char)] and List[(Int,T)]:

import stainless.collection._
object Test {
    type T = Char
    case class C(u: List[(Int,T)]) 
}

Having a list of pairs as opposed to List[T] seems necessary to trigger the problem.

Maybe tuples are not entirely traversed when expanding type synonyms?