massive increase in expanded code size for deriving.show

[oandrieu]

While using [@@deriving show] on a not-so-small-ish AST (~ 100 type declarations with a large clump of 60 mutually recursive types), I see that switching from ppx_deriving 5.2.1 to 6.0.3 resulted in massive increase of the code size after preprocessing.

With a ppx_deriving 5.2.1, there's rougly a ×3 file size increase, but with 6.0.3 it's more like ×100 and then the OCaml compiler fails with a stack overflow. In the output I see that many pretty-printing functions are repeated multiple times.

It's unclear to me if I'm using the annotations incorrectly, or using the ppx incorrectly.
(I'll try to come up with a repro case.)

[oandrieu]

Oh OK, I understand, that's because I have a deriving annotation on every typedef in a mutually recursive type definition:

type tutu =
  | VARIANT1
  | VARIANT2 of tutu
[@@deriving show]

and toto =
  { fielda : bool
  ; fieldb : tutu
  }
[@@deriving show]

I wasn't aware the annotation was only needed on one of the typedefs.
Still, the redundant annotations were harmless in ppx_deriving 5.2.1. Is this intended ?