Compiling the following, ```scala object Test { // The identity on Unit type Id[X] = X match { case _ => X } def foo[T](it: Id[T]) = ??? foo(()) } ``` with `-Xprint-types -Ytest-pickler -Yprint-pos -Yprint-pos-syms` as in `CompilationTests.pickling` results in a round trip failure, ``` miles@tarski:dotty (master)% diff before-pickling.txt after-pickling.txt 33c33 < <<Test.foo:([T](it: T): scala.Nothing)>@<118..121>[scala.Unit]: --- > <<Test.foo:([T](it: Test.Id[T]): scala.Nothing)>@<118..121>[scala.Unit]: ```