(type A extern (enum (B (x u32) (y u32))))

(decl get_a (A) u32)
(extern extractor get_a get_a)

(decl pure partial u32_pure (u32) u32)
(extern constructor u32_pure u32_pure)

(decl entry (u32) u32)
(rule (entry x @ (get_a a1))
      (if-let (get_a a2) x)
      (if-let (A.B p q) a1)
      (if-let r (u32_pure p))
      r)