[GHC] #5642: Deriving Generic of a big type takes a long time and lots of space

[GHC]

#5642: Deriving Generic of a big type takes a long time and lots of space
-------------------------------------+-------------------------------------
        Reporter:  basvandijk        |                Owner:  bgamari
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.3
      Resolution:                    |             Keywords:  deriving-
                                     |  perf, Generics
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:  T5642
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by nh2):

 I just filed a duplicate of this (#11991) with another easy-to-run repro
 that demonstrates that it's precisely O(n²) for sum types:
 https://github.com/nh2/ghc-generics-deriving-is-slow/

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5642#comment:33>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler