Add comment about arity

I'm not sure what the significance of the "arity" of a primtive
TyCon is.  They aren't necessarily saturated, so it's not that.

I rather think that arity is only relevant for
	SynTyCon
	AlgTyCon
	CoercionTyCon

This comment (and commit message) is just an aide memoire.

diff --git a/compiler/types/TyCon.lhs b/compiler/types/TyCon.lhs
index fc27995..3ae5c3e 100644 (file)
--- a/compiler/types/TyCon.lhs
+++ b/compiler/types/TyCon.lhs
@@ -173,7 +173,8 @@ data TyCon
        tyConUnique   :: Unique,
        tyConName     :: Name,
        tyConKind     :: Kind,
-       tyConArity    :: Arity,
+       tyConArity    :: Arity,         -- SLPJ Oct06: I'm not sure what the significance
+                                       --             of the arity of a primtycon is!
 
        primTyConRep  :: PrimRep,
                        -- Many primitive tycons are unboxed, but some are