#14302: ghc panic on simple program -------------------------------------+------------------------------------- Reporter: aberent | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash or panic | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by aberent): This appears to be an error in the error handling. Once I fix the compilation errors reported by ghci, ghc is happy to compile it. FYI my fixed code is: {{{ module Tiltmaze (solve) where import Data.Sequence as Sequence -- A maze is a grid of empty cells and walls -- true means wall type Maze = Seq (Seq Bool) data Direction = North | South | East | West deriving (Eq, Show) directions = [North, South, East, West] step :: Direction -> Int -> Int -> (Int, Int) step d x y | d == North = (x, y-1) | d == South = (x, y+1) | d == East = (x+1, y) | d == West = (x-1, y) solve :: Maze -> Int -> Int -> Int -> Int -> Bool solve m sx sy tx ty | sx == tx && sy == ty = True | otherwise = let solved m x y d | x' < 0 = False | y' < 0 = False | x' >= Sequence.length m = False | y' >= Sequence.length (m `index` x') = False | not ((m `index` x') `index` y') = False | otherwise = solve m' x' y' tx ty where (x', y') = step d x y m' = update x (update y False (m `index` x)) m in any (solved m sx sy) directions }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14302#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler