toCcc' rule not firing with GHC 8.2.2 about concat HOT 4 CLOSED

On the flip side it does make compiling the examples wayyyy faster :)

from concat.

Is there a way I can help?

from concat.

Thanks to help from @kosmikus, I found the problem here.

In ConCat.Plugin from pull #37:

isMonoTy :: Type -> Bool
isMonoTy (TyConApp _ tys)      = all isMonoTy tys
isMonoTy (AppTy u v)           = isMonoTy u && isMonoTy v
#if MIN_VERSION_GLASGOW_HASKELL(8,2,0,0)

#else
isMonoTy (ForAllTy (Anon u) v) = isMonoTy u && isMonoTy v
#endif
isMonoTy (LitTy _)             = True
isMonoTy _                     = False

The omitted test handles function types, which are the only types given as an argument to toCcc'. The isMonoTy thus always yields False, and so the rewriting fails every time.

I made a very simple fix: use the FunTy pattern synonym regardless of GHC version. The new definition:

isMonoTy :: Type -> Bool
isMonoTy (TyConApp _ tys) = all isMonoTy tys
isMonoTy (AppTy u v)      = isMonoTy u && isMonoTy v
isMonoTy (FunTy u v)      = isMonoTy u && isMonoTy v
isMonoTy (LitTy _)        = True
isMonoTy _                = False

This change fixes the immediate issue with 8.2.2. I'll open another issue for the next breakage.

from concat.

from concat.