#13258: GHC head 8.1.20170209 does not compile package 'mono-traversable' -------------------------------------+------------------------------------- Reporter: clinton | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Not sure if this is a bug in 'mono-traversable' or GHC but I thought it was worth reporting in any case. GHC head 8.1.20170209 is the version used: {{{ Configuring mono-traversable-1.0.1.1... Preprocessing library mono-traversable-1.0.1.1... [1 of 5] Compiling Data.MonoTraversable ( src/Data/MonoTraversable.hs, .stack-work/dist/x86_64-linux/Cabal-1.25.0.0/build/Data/MonoTraversable.o ) /tmp/stack12856/mono- traversable-1.0.1.1/src/Data/MonoTraversable.hs:144:13: error: • The default type signature for omap: forall (f :: * -> *) a. (Functor f, Element (f a) ~ a, f a ~ mono) => (a -> a) -> f a -> f a does not match its corresponding non-default type signature • When checking the class method: omap :: forall mono. MonoFunctor mono => (Element mono -> Element mono) -> mono -> mono In the class declaration for ‘MonoFunctor’ | 144 | default omap :: (Functor f, Element (f a) ~ a, f a ~ mono) => (a -> a) -> f a -> f a | ^^^^ }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13258 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler