#15558: Locally handling an empty constraint -------------------------------------+------------------------------------- Reporter: Ericson2314 | Owner: (none) Type: task | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple error/warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): I'm not quite sure I understand what this ticket is about, but it's worth noting that inaccessible code turned from an error to a warning in GHC 8.6.1, so your code does in fact compile as-is on 8.6.1: {{{ $ /opt/ghc/8.6.1/bin/ghci Bug.hs GHCi, version 8.6.0.20180810: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Asdf ( Bug.hs, interpreted ) Bug.hs:49:3: warning: [-Winaccessible-code] • Couldn't match type ‘[b]’ with ‘Int’ Inaccessible code in a pattern with constructor: X :: Sing Int, in a case alternative • In the pattern: X In a case alternative: X -> Bar 0 undefined In the expression: \case X -> Bar 0 undefined Y -> Bar [] False | 49 | X -> Bar 0 undefined -- can't make this happy | ^ }}} Does this satisfy your use case? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15558#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler