#12881: GHC 8.0.2 regression involving OVERLAP annotations -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 8.0.2-rc1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): It should be noted that if you add explicit `OVERLAP*` annotations: {{{#!hs {-# LANGUAGE FlexibleInstances #-} module Bug where class Arbitrary a where shrink :: a -> [a] shrink _ = [] instance {-# OVERLAPPABLE #-} Arbitrary a instance {-# OVERLAPPING #-} Arbitrary Int }}} Then it will compile again, so there's at least a simple workaround. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12881#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler