#8356: Strangeness with FunDeps -------------------------------------------------+------------------------- Reporter: ksf | Owner: Type: bug | Status: Priority: normal | closed Component: Compiler | Milestone: Resolution: fixed | Version: 7.7 Operating System: Unknown/Multiple | Keywords: Type of failure: GHC rejects valid program | Architecture: Test Case: | Unknown/Multiple typecheck/should_fail/tcfail170 | Difficulty: Blocking: | Unknown | Blocked By: | Related Tickets: -------------------------------------------------+------------------------- Comment (by monoidal): The testcase `tcfail170` triggers a `pprTrace` in `FunDeps.lhs`. Is this intended? {{{ $ ghc-7.7.20131027 tcfail170 [1 of 1] Compiling ShouldFail ( tcfail170.hs, tcfail170.o ) cic main:ShouldFail.C{tc roB} [[p{tv aoE} [sk]], [q{tv aoF} [sk]]] ([a{tv aoC} [tv]], [b{tv aoD} [tv]]) [(aoE, p{tv aoE} [sk])] [(aoF, q{tv aoF} [sk])] [(aoE, p{tv aoE} [sk])] [] tcfail170.hs:7:10: Illegal instance declaration for ‛C [p] [q]’ The coverage condition fails in class ‛C’ for functional dependency: ‛a -> b’ Reason: lhs type ‛[p]’ does not determine rhs type ‛[q]’ In the instance declaration for ‛C [p] [q]’ }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8356#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler