#8779: Exhaustiveness checks for pattern synonyms -------------------------------------+------------------------------------- Reporter: nomeata | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.8.1 checker) | Keywords: Resolution: | PatternSynonyms Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): What you say is attractive Reid, but consider a snoc-view of a list. We might want to say that the two patterns `SnocNil` and `SnocCons` are exhaustive, but the fact that they are really is something that needs proof (`SnocCons` at least is defined via a view). Moreover, if we match on `SnocCons` and miss out `SnocNil` we'd like to report `SnocNil` as missing, rather than `[]`. And vice versa with matching on `SnocNil` and omitting `SnocCons`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8779#comment:32 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler