#10697: Change template-haskell API to allow NOUNPACK, lazy annotations -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Template Haskell | Version: 7.10.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #5290, #8347 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * cc: adamse (added) Comment: It turns out that even without considering `NOUNPACK`, `Strict` and `TemplateHaskell` don't play well together at the moment. This code: {{{#!hs {-# LANGUAGE StrictData, TemplateHaskell #-} import Language.Haskell.TH data T a = T !a a ~a $(return []) main :: IO () main = putStrLn $(reify ''T >>= stringE . show) }}} produces this output (prettied up a bit): {{{#!hs TyConI (DataD [] Main.T [KindedTV a_1627391747 StarT] [NormalC Main.T [ (IsStrict, VarT a_1627391747) , (NotStrict,VarT a_1627391747) , (NotStrict,VarT a_1627391747) ]] []) }}} Which is pretty darn misleading, since the second argument is actually strict! That being said, I'm not exactly sure what it ''should'' output here. One might could argue is should be `(IsStrict, NotStrict, IsLazy)`, but then again, the definition of `NotStrict` depends on whether `StrictData` is enabled or not. If we output `(Strict, NotStrict, IsLazy)`, then would splicing the TH code for that datatype into a module without `StrictData` fail (since `IsLazy` implies a laziness annotation)? Perhaps TH should check whether `StrictData` is on and splice accordingly. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10697#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler