Need compiler error to disallow enhancing a recursive type bound with a structure

[DPUkyle]

See example:

Kaboom.gs

structure Kaboom {
  property Bang : String
}

KaboomEnhancement.gsx

enhancement KaboomEnhancement : Iterable<T extends Kaboom> {}

TNT.gsp

uses java.nio.file.Paths

var somePath = Paths.get("", {}).toFile() //returns a Path, which is Iterable<Path>

This example creates a cycle in TypeInfo verification within the compiler. For now, we should disallow enhancing recursive types bound by a structure, like KaboomEnhancement.