Artifact of pickled type splices

During quote reification a quote'{ ... F[t.Underlying] ... } will be transformed into'{ @SplicedType type T$1 = t.Underlying ... F[T$1] ... } to have a tree fort.Underlying. This artifact is removed during quote unpickling.

See PickleQuotes.scala and PickledQuotes.scala

Adding this annotation in source has undefined behavior at compile-time