Unresolable collision between ocaml packages

[Brett Gilio]

Hi all,

I like to make meta-packages that I can pass to `guix environment
--ad-hoc` for development. I have the following meta package for ocaml

(define-public meta-ocaml
  (package
   (inherit %meta-base)
   (name "meta-ocaml")
   (propagated-inputs
    `(("meta-emacs" ,meta-emacs)
      ("darcs" ,darcs)
      ("dune" ,dune)
      ("emacs-tuareg" ,emacs-tuareg)
      ("gcc-toolchain" ,gcc-toolchain)
      ("m4" ,m4)
      ("make" ,gnu-make)
      ("mercurial" ,mercurial)
      ("ocaml" ,ocaml)
      ("ocaml-base" ,ocaml-base)
      ("ocaml-core" ,ocaml-core)
      ("ocaml-ctypes" ,ocaml-ctypes)
      ("ocaml-findlib" ,ocaml-findlib)
      ("ocaml-merlin" ,ocaml-merlin)
      ("ocaml-ounit" ,ocaml-ounit)
      ("oocaml-parsexp"
       ,ocaml-parsexp)
      ("ocaml-utop" ,ocaml-utop)
      ("opam" ,opam)
      ("rsync" ,rsync)))))


When trying to use that in an environment, I am getting the following
backtrace claiming there is a collision that I assume is not getting
resolved in its usual fashion.

Backtrace:
           6 (primitive-load "/gnu/store/k45l4ph58xakp3f52kmridr9wyc…")
In guix/build/profiles.scm:
    157:2  5 (build-profile "/gnu/store/c2khaalrpy7cdyr8k4lawgqnbzs…" …)
In unknown file:
           4 (hash-for-each #<procedure 105c180 at guix/build/union…> …)
           3 (hash-for-each #<procedure 10b3900 at guix/build/union…> …)
           2 (hash-for-each #<procedure 110b180 at guix/build/union…> …)
           1 (hash-for-each #<procedure 14368c0 at guix/build/union…> …)
           0 (scm-error misc-error #f "~A ~S" ("union-build: col…" …) …)

ERROR: In procedure scm-error:
union-build: collision between file and directories ((files
("/gnu/store/h1w5b2l1wny94cnfqm46w12nm3w8wz2k-ocaml-num-1.1/lib/ocaml/site-lib/stublibs"))
(dirs
("/gnu/store/93lp6k3d58dfc8gvx9zd70szapsb5kv6-ocaml-base-0.11.1/lib/ocaml/site-lib/stublibs"
"/gnu/store/7vrg8apsnl6hg9vsszpgcq4ymvz9whap-ocaml-core-0.11.3/lib/ocaml/site-lib/stublibs"
"/gnu/store/iz6wzz9sm4qnal2wlqi66blm8mb35zxv-ocaml-core-kernel-0.11.1/lib/ocaml/site-lib/stublibs"
"/gnu/store/zrpcrfrmyanhqpvhxkclpgiq2sp7k1ip-ocaml-bin-prot-0.11.0/lib/ocaml/site-lib/stublibs"
"/gnu/store/n70q0ypcv74vpwdd0354rjxi7mv9y1rf-ocaml-ppx-inline-test-0.12.0/lib/ocaml/site-lib/stublibs"
"/gnu/store/q42ayh04wy70pl2xdm2yp2i0s8yh5g7b-ocaml-ppx-expect-0.12.0/lib/ocaml/site-lib/stublibs"
"/gnu/store/cwijnaplps7zbby3xq21spjk4fgxpd35-ocaml-spawn-0.13.0/lib/ocaml/site-lib/stublibs"
"/gnu/store/09b6pfbw3n1j2qqni822wjjixh48qwfp-ocaml-lambda-term-1.13/lib/ocaml/site-lib/stublibs"
"/gnu/store/zlibrm9b6pa8hgwmjigzwm2cq3kb4y1r-ocaml-lwt-4.1.0/lib/ocaml/site-lib/stublibs"
"/gnu/store/qzkydyr8rrbpfk2lfjynnhgdbavf4kh0-ocaml-ssl-0.5.7/lib/ocaml/site-lib/stublibs"
"/gnu/store/sqkcaap13wgbjdqnjia8hi12rf2p5qf1-ocaml-dose3-5.0.1/lib/ocaml/site-lib/stublibs"
"/gnu/store/wnl6maf9s6ksvszyy9q2bz0psiy1h15j-ocaml-mccs-1.1+9/lib/ocaml/site-lib/stublibs")))


If formatting is bad in this email, here are plaintext pastes.

meta-packages.scm : http://ix.io/1L1A

backtrace : http://ix.io/1L1B