Reported by Eugeniy D on scala-internals.

class C[@specialized(Double) A]()
class D[@specialized(Double) A]() {
    val (a, b) = (1, 2)
    val c = new C[A]()
}

Crashes the backend. In 2.12, GenBCode: unexpected type representation reached the backend: => Tuple2. In 2.11 during GenICode: error: Unknown type: => Tuple2, => Tuple2.

  <specialized> class D$mcD$sp extends D {
...
    <specialized> def <init>(): D$mcD$sp = {
      D$mcD$sp.super.<init>();
      D$mcD$sp.this.x$1 = {
        private[this] val x1: Tuple2 = (new Tuple2$mcII$sp(1, 2): Tuple2);
        case4(){
          if (D$mcD$sp.this.x1.ne(null))
...

when generating code for loading D$mcD$sp.this.x1, its sym.info is a NullaryMethodType. Note that this is in the specialized subclass D$mcD$sp, the class D also has a definition x1 which seems to have a good type. Maybe a bug in duplicators? Just a guess.