#11822: Pattern match checker exceeded (2000000) iterations -------------------------------------+------------------------------------- Reporter: j.waldmann | Owner: gkaracha Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1-rc3 Resolution: | Keywords: | PatternMatchWarnings Operating System: Unknown/Multiple | Architecture: x86_64 Type of failure: Compile-time | (amd64) performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dbaynard): I've just encountered this (on 8.6.3) while making some changes to stack. I'll try an option which doesn't need to do so much checking. But this appears much smaller than the previous examples here. {{{#!haskell {#- LANGUAGE OverloadedLists -#} {#- LANGUAGE PatternSynonyms -#} {#- LANGUAGE GeneralisedNewtypeDeriving -#} import Data.Seq (Seq, pattern (:<|)) import Data.Set (Set) newtype SiblingDependencies = SiblingDependencies Int deriving (Eq, Ord, Enum, Integral, Real, Num) newtype Depth = Depth Int deriving (Eq, Ord, Enum, Integral, Real, Num) data TreeNode prefix = OnlyChild prefix | LeafLast prefix | LeafMid prefix | NodeLast prefix | NodeMid prefix | PrefixedLast prefix (Seq SiblingDependencies) (Set PackageName) Depth | PrefixedMid prefix (Seq SiblingDependencies) (Set PackageName) Depth mkTreeNode :: prefix -> Seq SiblingDependencies -> Set PackageName -> Depth -> TreeNode prefix mkTreeNode t [] _ _ = OnlyChild t mkTreeNode t [0] [] _ = LeafLast t mkTreeNode t [_] [] _ = LeafMid t mkTreeNode t [0] _ 0 = LeafLast t mkTreeNode t [_] _ 0 = LeafMid t mkTreeNode t [0] _ _ = NodeLast t mkTreeNode t [_] _ _ = NodeMid t mkTreeNode t (0 :<| ns) ds depth = PrefixedLast t ns ds depth mkTreeNode t (_ :<| ns) ds depth = PrefixedMid t ns ds depth }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11822#comment:22 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler