#14290: Strictness bug with existential contexts on data constructors -------------------------------------+------------------------------------- Reporter: simonmar | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.2.2 Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The following: {{{ {-# LANGUAGE ExistentialQuantification #-} module Main (main) where main :: IO () main = r `seq` return () r :: Rec r = Rec{ a = error "xxx", b = 3, c = True } class C t instance C Bool data Rec = forall t. C t => Rec { a :: () , b :: !Int , c :: t } }}} Fails with `error "xxx"`, when it should succeed. The problem is that the strictness signature for the data con wrapper doesn't take into account the dictionary fields. I have a patch which I'll upload to Phabricator shortly... -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14290 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler