Created attachment 582124 [details, diff]
Patch agains gentoo-tree to add guile-2.2.6, SLOT=2.2 + patches
dev-scheme/guile as native support for parallel installations for a while , and I have experimented it on the lisp-overlay [2,3].
This bug aims as tracking progress on SLOTting guile-2.2 series, fixing reverse dependencies to use the 2.2 slot when available, and ensure dead packages non compatible with guile-2.2 to be able to use guile-1.8 or 2.0.
If SLOTting guile-2.2 is a success, we will be able to start slotting guile 2.0 as well if some packages are strictly depending on a specific pre-2.2 version. guile-3.0 is also on the way.
Depending packages will be required to update there dependencies to use the 2.2 slot, and failing packages should be added to bug #640116.
Comments are welcome either to gentoo-lisp project ML or IRC Channel. Please avoid scheme@ mail alias as I cannot receive them.
From the NEWS file in version 3.0.0:
* Changes to the distribution
** New effective version
The "effective version" of Guile is now 3.0, which allows parallel
installation with other effective versions (for example, the older Guile
2.2). See "Parallel Installations" in the manual for full details.
Notably, the `pkg-config' file is now `guile-3.0', and there are new
`guile-3' and `guile-3.0' features for `cond-expand'.