#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 ilovezfs): Here's another instance in the wild that just got released: https://github.com/purescript/purescript/issues/2421. {{{ src/Control/Monad/Supply/Class.hs:30:10: error: • Couldn't match type ‘m’ with ‘StateT s m’ ‘m’ is a rigid type variable bound by the instance declaration at src/Control/Monad/Supply/Class.hs:30:10 Expected type: StateT s m Integer Actual type: StateT s (StateT s m) Integer etc. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12784#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler