#12784: Typechecker regression in GHC 8.0.2 involving DefaultSignatures -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: merge Priority: highest | Milestone: 8.0.2 Component: Compiler | Version: 8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D2682 Wiki Page: | -------------------------------------+------------------------------------- Comment (by rwbarton): And the relevant code (excerpted from https://github.com/purescript/purescript/blob/master/src/Control/Monad/Suppl...): {{{#!hs class Monad m => MonadSupply m where fresh :: m Integer peek :: m Integer default fresh :: MonadTrans t => t m Integer fresh = lift fresh default peek :: MonadTrans t => t m Integer peek = lift peek instance MonadSupply m => MonadSupply (StateT s m) instance (Monoid w, MonadSupply m) => MonadSupply (WriterT w m) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12784#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler