serras/scion-class-browser — Issue #19: GHC 7.2.2 fails to build (FlexibleInstances)
Author: codeweaverx
Created: 2012-01-29 23:40:12+00:00
State: open

On ghc7.2.2, I several of this kind of error in Json.hs and Query.hs

src/Scion/PersistentBrowser/Instances/Json.hs:90:10:
Illegal instance declaration for `ToJSON DbTyVar'
(All instance types must be of the form (T a1 ... an)
where a1 ... an are *distinct type variables*,
and each type variable appears at most once in the instance head.
Use -XFlexibleInstances if you want to disable this.)
In the instance declaration for `ToJSON DbTyVar'

I was able to build upon adding FlexibleInstances to the relevant files, but this may not be the correct fix.

(discovered as a result of this thread over on sourceforge: http://sourceforge.net/projects/eclipsefp/forums/forum/371922/topic/4777573/index/page/2 )