Valac generates invalid C source (const gchar * + const char *)

[Hibou57 (Yannick Duchêne)]

Using the source given as an attached file (not the real application, I stripped as much as possible from it), compilation using the options given below, terminates with this error:

    Compilation failed: 1 error(s), 0 warning(s)
    <cwd>/bug.vala.c: In function ‘setup_xdg_data_dirs_env_variable’:
    <cwd>/bug.vala.c:294:21: erreur: invalid operands to binary + (have ‘const gchar *’ and ‘const char *’)

Using `valac` invoked as in (recalled in the attached source file):

    valac \
       --enable-checking \
       --enable-experimental \
       --enable-experimental-non-null \
       --enable-version-header \
       --pkg gtk+-3.0 \
       --vapidir=/usr/share/vala-0.14/vapi/ \
       "bug.vala";

-----

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: valac 0.14.2-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-37.58-generic-pae 3.2.35
Uname: Linux 3.2.0-37-generic-pae i686
ApportVersion: 2.0.1-0ubuntu17.1
Architecture: i386
CheckboxSubmission: 9b39dc487a858b4cfa15c3a2f5fa50d5
CheckboxSystem: d00f84de8a555815fa1c4660280da308
Date: Tue Feb 19 07:48:34 2013
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release i386 (20120423)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=fr_FR.UTF-8
 SHELL=/bin/bash
SourcePackage: vala-0.14
UpgradeStatus: No upgrade log present (probably fresh install)

[Hibou57 (Yannick Duchêne) (yannick-duchene)]

I've noticed the error disappears if this `valac` option is removed:

    --enable-experimental-non-null

(I'm unlucky, as I love the idea of this kind of check).

As a workaround for now, running `valadoc` with the same option, does not make it fails, checks the source and points any error about conversion attempt like from `string?` to `string`. Finally I can disable the option for compiling and keep it for document generation, which becomes a kind of added check.

Would still be better if using this option would not result in invalid C source generation.

How is it supposed to impact C source generation? Though it was only about static checking...