#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: deriving, | PatternMatchWarnings 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 simonpj):
I thought you were requesting that we never emit inaccessible code warnings for derived code (regardless of whether -Winaccessible-code is enabled or not).
Correct. So if we switch off `-Winaccessible-code` when typechecking derived code, that would do job. And we try to; see {{{ -- Now GHC-generated derived bindings, generics, and selectors -- Do not generate warnings from compiler-generated code; -- hence the use of discardWarnings tc_envs@(tcg_env, tcl_env) <- discardWarnings (tcTopBinds deriv_binds deriv_sigs) ; }}} in `TcRnDriver`. Unfortunately the `dicardWarnings` only discards warnings generated while doing `tcTopBinds`. But `tcTopBinds` also creates a bunch of constraints that don't "see" that `discardWarnings`. If instead switched off the warning `DynFlags`, and captured the `DynFlags` in an implication, the warning suppression would still work on the constraints. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15398#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler