#15164: Slowdown in ghc compile times from GHC 8.0.2 to GHC 8.2.1 when doing Called arity analysis -------------------------------------+------------------------------------- Reporter: flip101 | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.6.1 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: Operating System: Linux | 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 nomeata): Ha, the code still compiles, and does so quickly with all versions, if I simply remove the contexts from the instance declarations, e.g. {{{ -instance (Rule f Expression, Rule f Name) => Rule f ActualDesignator where +instance Rule f ActualDesignator where }}} This also lets me remove `UndecidableInstances`. See this commit: https://github.com/nomeata/parser- calledarityanalysis/commit/cb2e23b081d1016278feaa1397ad62a1672a52cf @flip101, I understand that this is minimized code. Can you check your real code if you really need the contexts in the instance declarations, and if the problem goes away when you remove them? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15164#comment:15 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler