Multiple instance pragmas

Domínguez, Facundo facundo.dominguez at
Mon Nov 25 16:26:17 UTC 2019

Dear devs,

I have a program [1] which depends on the ability to specify some instances
to be both overlappable and incoherent.

GHC so far, allows only one of the OVERLAPPABLE or INCOHERENT pragmas to be
specified per instance. One can still have an overlappable and incoherent
instance by using -XIncoherenInstances, but this extension is deprecated.

Is there any chance that a patch is accepted to allow multiple instance
pragmas? And if not, what would the reason for this constraint?


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>

More information about the ghc-devs mailing list