#show_module prints types incorrectly

[vicuna]

Original bug ID: 6587
Reporter: jcf
Assigned to: @garrigue
Status: resolved (set by @garrigue on 2017-03-16T00:22:57Z)
Resolution: fixed
Priority: normal
Severity: feature
Version: 4.02.0+beta1 / +rc1
Target version: undecided
Fixed in version: 4.06.0 +dev/beta1/beta2/rc1
Category: typing
Child of: #4791
Monitored by: @gasche @hcarty

Bug description

With the code below, the OCaml toplevel prints

module M : sig type in_channel val f : in_channel -> in_channel end

that is, it prints the two types M.in_channel and Pervasives.in_channel the same way. (I found this while playing with camlzip, which has a module containing a type called in_channel.)

Steps to reproduce

module M = struct
type in_channel
let f (c: Pervasives.in_channel) : in_channel = assert false
end;;

#show_module M;;

[vicuna]

Comment author: @garrigue

The problem is specific to Pervasives: omitting the prefix is hard-wired in Printtyp.
Note that this is not specific to #show_module: this is just the behavior of the standard printer.

[vicuna]

Comment author: @Octachron

I have proposed a patch in #1109 to only perform this Pervasives prefix elision when it is unambiguous in the current printing environment.

[vicuna]

Comment author: @garrigue

Merge #1109 after light edit, in commit 929b99b.
Thanks for the code.