#15398: GADT deriving Ord generates inaccessible code in a pattern with constructor. ---------------------------------+-------------------------------------- Reporter: philderbeast | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.2.2 Resolution: | Keywords: Operating System: MacOS X | Architecture: x86_64 (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ---------------------------------+-------------------------------------- Comment (by RyanGlScott): Replying to [comment:2 philderbeast]:
Is there no way for GHC to do the derivation without the generated code having warnings?
In theory this would be possible, but it would significantly complicate the algorithm that `deriving Ord` uses to generate code. Currently, the algorithm is implemented as a pure function over the abstract syntax tree, but changing it to not generate inaccessible cases would require it to propagate typing information in a non-trivial way. I'm skeptical that such a large change would pay its weight, especially since the workaround (just use `-Wno-inaccesible-code`) is so simple. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15398#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler