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authorJoey Hess2018-04-30 09:03:46 -0400
committerJoey Hess2018-04-30 09:03:46 -0400
commit14fe4c4d6b5a29be94ecfc0572e0f9a9a081e795 (patch)
tree38ad23b09bd21a8569568335a13bfde9c16e79c1 /src/Propellor/Property/DiskImage
parent96ea8e04251bc23dd27faf1f486a2a9f9c29ff98 (diff)
fix broken SemigroupMonoid transition <<loop>>
Turns out that with ghc 8.2.2, the instructions given on the page don't work. And the cppless variant that I had compiles, but into effectively mappend = mappend so it loops. The only way I can see to make it work without cpp is to use mappend = (Sem.<>) which is ugly and a land mine waiting to explode if someone changes it to a nicer mappend = (<>) with a newer version of ghc which will compile it and work ok, while breaking it with 8.2.2. Sigh. I posted to haskell-cafe about this.
Diffstat (limited to 'src/Propellor/Property/DiskImage')
-rw-r--r--src/Propellor/Property/DiskImage/PartSpec.hs2
1 files changed, 1 insertions, 1 deletions
diff --git a/src/Propellor/Property/DiskImage/PartSpec.hs b/src/Propellor/Property/DiskImage/PartSpec.hs
index 0698d806..652b53c8 100644
--- a/src/Propellor/Property/DiskImage/PartSpec.hs
+++ b/src/Propellor/Property/DiskImage/PartSpec.hs
@@ -189,7 +189,7 @@ instance Sem.Semigroup PartLocation where
instance Monoid PartLocation where
mempty = Middle
- mappend = (<>)
+ mappend = (Sem.<>)
partLocation :: PartSpec PartLocation -> PartLocation -> PartSpec PartLocation
partLocation (mp, o, p, _) l = (mp, o, p, l)