#14228: PatternSynonyms Non-exhaustive with UnboxedSums -------------------------------------+------------------------------------- Reporter: guibou | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Resolution: | Keywords: UnboxedSums, | PatternSynonyms 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: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * keywords: UnboxedSum, PatternSynonyms => UnboxedSums, PatternSynonyms Comment: Wow! Great catch. Indeed, the `ddump-simpl` output for that program looks mighty suspicious. I'll post an abridged version below: {{{#!hs -- RHS size: {terms: 14, types: 20, coercions: 0, joins: 0/0} $mJust' :: forall (r :: TYPE rep) a. Maybe' a -> (a -> r) -> (Void# -> r) -> r $mJust' = \ (@ (rep :: RuntimeRep)) (@ (r :: TYPE rep)) (@ a) (scrut :: Maybe' a) (cont :: a -> r) _ -> case scrut of { (#_|#) x -> cont x; (#|_#) ipv -> patError "Bug.hs:8:19-27|case"# } -- RHS size: {terms: 17, types: 21, coercions: 0, joins: 0/0} $mNothing' :: forall (r :: TYPE rep) a. Maybe' a -> (Void# -> r) -> (Void# -> r) -> r $mNothing' = \ (@ (rep :: RuntimeRep)) (@ (r :: TYPE rep)) (@ a) (scrut :: Maybe' a) (cont :: Void# -> r) _ -> case scrut of { (#_|#) ipv -> patError "Bug.hs:11:20-29|case"#; (#|_#) ds -> case ds of { () -> cont void# } } }}} Just //look// at that rubbish! The matchers for `Just'` and `Nothing'` each take a failure continuation as an argument, but appear to ignore them completely and just proceed directly to `patError` in case the expected pattern wasn't matched. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14228#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler