#12444: Regression: panic! on inaccessible code with constraint -------------------------------------+------------------------------------- Reporter: zilinc | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): I spent some time investigating. Here's a smaller test case. This program, closely related to the original, makes the constraint solver loop: {{{ data Nat = Zero | Succ Nat data SNat (n :: Nat) type family (:+:) (a :: Nat) (b :: Nat) :: Nat where m :+: Zero = m m :+: (Succ n) = Succ (m :+: n) foo :: SNat (Succ c) -> SNat b -> SNat (Succ (c :+: b)) foo _ x = x }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12444#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler