That has nothing to do with type erasure. Type aliases are not distinct from the underlying type, even at compile time. You needed value classes, not aliases.

That has nothing to do with type erasure. Type aliases are not distinct from the underlying type, even at compile time. You needed value classes, not aliases. example: object Example { type IdA = Long type IdB = Long def usesA(i: IdA) = "it's an A" case class IdC(i: Long) extends AnyVal case class IdD(i: Long) extends AnyVal def usesC(i: IdC) = "it's a C" val a: IdA = 1L val b: IdB = 2L val c = IdC(3L) val d = IdD(4L) usesA(a) usesA(b) usesC(c) // these won't compile // usesC(d) // usesC(a) }