Defining a wired-in type of a different kind

Jan van Br├╝gge jan at vanbruegge.de
Wed Apr 3 11:06:11 UTC 2019


Hi,

when trying to get familiar with the GHC code base for my Bachelor's
thesis. I followed the GHC Wiki, especially the case study about the
bool type.
Now I wanted to add a new kind and a new type inhabiting this kind
(without having to expose a data constructor, so without datatype
promotion).

So in TysWiredIn.hs I added the new TyCons and added them to the list of
wired-in types:

-- data Row a b
rowKindCon :: TyCon
rowKindCon = pcTyCon rowKindConName Nothing [alphaTyVar, betaTyVar] []

rowKind :: Kind
rowKind = mkTyConTy rowKindCon

-- data RNil :: Row a b
rnilTyCon :: TyCon
rnilTyCon = mkAlgTyCon rnilTyConName [] rowKind [] Nothing []
    (mkDataTyConRhs [])
    (VanillaAlgTyCon (mkPrelTyConRepName rnilTyConName))
    False

rnilTy :: Type
rnilTy = mkTyConTy rnilTyCon


I also added two new empty data decls to ghc-prim, but if I inspect the
kind of RNil it is not Row, but Type. So I think I am either
understanding res_kind wrong or I have to do something completely different.
I am also not sure how to verify that the code in TysWiredIn.hs is
working at all, from all what I can tell it could just be the
declarations in ghc-prim that result in what I see in ghci.

Thank you and sorry for my beginner question
Jan

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