Re: [commit: ghc] master: Allow deriving Typeable for more tycons (92191a3)

Hi Simon, Yes. I still need to do some more work, though, because one thing is not yet working as I would like it to. Right now, if you define a datatype with -XDataKinds, you can derive Typeable for the promoted constructors: data N = Z | S N deriving Typeable -- for N

deriving instance Typeable Z deriving instance Typeable S

Note that the last two Typeable instances can only be given by standalone deriving. However, in case the user specifies -XAutoDeriveTypeable, I would expect all three instances to be unnecessary. Right now, however, we do not automatically derive Typeable instances for promoted constructors. This is because they are not tycl_decls (as in makeDerivSpecs in TcDeriv). What's the best way to easily get hold of all the promoted tycons in a module? Thanks, Pedro On Wed, May 8, 2013 at 10:37 AM, Simon Peyton-Jones wrote:

Pedro

Surely should be some user-manual change to go with this?

Simon

| -----Original Message----- | From: ghc-commits-bounces@haskell.org [mailto:ghc-commits- | bounces@haskell.org] On Behalf Of José Pedro Magalhães | Sent: 07 May 2013 13:27 | To: ghc-commits@haskell.org | Subject: [commit: ghc] master: Allow deriving Typeable for more tycons | (92191a3) | | Repository : http://darcs.haskell.org/ghc.git/ | | On branch : master | | https://github.com/ghc/ghc/commit/92191a39a59a036fde4de926e2e322a2c50c84 | cf | | >--------------------------------------------------------------- | | commit 92191a39a59a036fde4de926e2e322a2c50c84cf | Author: Jose Pedro Magalhaes | Date: Tue May 7 09:16:29 2013 +0100 | | Allow deriving Typeable for more tycons | | >--------------------------------------------------------------- | | compiler/typecheck/TcDeriv.lhs | 3 ++- | 1 file changed, 2 insertions(+), 1 deletion(-) | | diff --git a/compiler/typecheck/TcDeriv.lhs | b/compiler/typecheck/TcDeriv.lhs index 7da30d19b..9b82ed6 100644 | --- a/compiler/typecheck/TcDeriv.lhs | +++ b/compiler/typecheck/TcDeriv.lhs | @@ -683,7 +683,8 @@ mkEqnHelp :: CtOrigin -> [TyVar] -> Class -> [Type] | -> Type | | mkEqnHelp orig tvs cls cls_tys tc_app mtheta | | Just (tycon, tc_args) <- tcSplitTyConApp_maybe tc_app | - , isAlgTyCon tycon -- Check for functions, primitive types etc | + , className cls == typeableClassName || isAlgTyCon tycon | + -- Avoid functions, primitive types, etc, unless it's Typeable | = mk_alg_eqn tycon tc_args | | otherwise | = failWithTc (derivingThingErr False cls cls_tys tc_app | | | | _______________________________________________ | ghc-commits mailing list | ghc-commits@haskell.org | http://www.haskell.org/mailman/listinfo/ghc-commits

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