On Dec 17, 2014, at 12:29 PM, Jan Stolarek <jan.stola...@p.lodz.pl> wrote: > > Why not implement repPlainTV like this: ? > > repPlainTV :: Core TH.Name -> DsM (Core TH.TyVarBndr) > repPlainTV (MkC nm) = return $ MkC (TH.PlainTV nm) >
In short, that's ill typed. We have > newtype Core a = MkC CoreExpr The idea behind this type is that its (phantom) type parameter tracks the type of the expression stored within. Of course, the thing within is always just a core expression. TH.PlainTV takes a TH.Name and produces a TH.TyVarBndr. But, nm is a CoreExpr and MkC is expecting a CoreExpr, so your suggestion wouldn't type check. The higher-level answer is that you're mixing levels. The goal in DsMeta is *not* to create the TH AST. It's to create *core expressions* that create the TH AST. Does this help? Richard _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://www.haskell.org/mailman/listinfo/ghc-devs