Re: Simplification of instances

2012/9/28 Simon Peyton-Jones :

Ahem. DFuns (what you get from is_dfun of a ClsInst) now have some "silent" arguments, that are added by GHC and are not part of the original instance declaration. See Note [Silent superclass arguments] in TcInstDcls.

But you don't want to print them. Just do what InstEnv.pprInstanceHdr does (in InstEnv) to drop the silent arguments.

I've added some more comments (commit to come).

Thanks! I've written a Haddock patch that drops the arguments. David