#8034: Missing ambiguity test for class methods -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.12.1 Component: Compiler (Type | Version: 7.7 checker) | Keywords: Resolution: | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by thomie): This is fixed in HEAD already, isn't it? The example from the description gives an ambiguity error at least. See the following commit for details: In f66e0e695b0377c469fbe877d4850fc0ebca2010: {{{ Author: Simon Peyton Jones <> Date: Wed Mar 4 11:59:47 2015 +0000 A raft of small changes associated with -XConstrainedClassMethods See Trac #7854. Specifically: * Major clean up and simplification of check_op in checkValidClass; specifically - use checkValidType on the entire method-selector type to detect ambiguity - put a specific test for -XConstrainedClassMethods * Make -XConstrainedClassMethods be implied by -XMultiParamTypeClasses (a bit ad-hoc but see #7854), and document in the user manual. * Do the checkAmbiguity test just once in TcValidity.checkValidType, rather than repeatedly at every level. See Note [When to call checkAmbiguity] * Add -XAllowAmbiguousTypes in GHC.IP, since 'ip' really is ambiguous. (It's a rather magic function.) * Improve location info for check_op in checkValidClass * Update quite a few tests, which had genuinely-ambiguous class method signatures. Some I fixed by making them unambiguous; some by adding -XAllowAmbiguousTypes }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8034#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler