[GHC] #11383: CAFs lose sharing due to implicit call stacks

[GHC]

#11383: CAFs lose sharing due to implicit call stacks
-------------------------------------+-------------------------------------
        Reporter:  simonmar          |                Owner:  gridaphobe
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  8.0.1-rc1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11298            |  Differential Rev(s):  Phab:D1912
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by gridaphobe):

 * status:  new => patch
 * differential:   => Phab:D1912


Comment:

 This will be (partially) fixed by D1912, which prevents GHC from inferring
 CallStack constraints for top-level definitions. You could still create
 the issue by making `x` a local binder inside `main`, but then again, the
 monomorphism restriction will usually be turned on and will prevent the
 inference.

 On a related note, do we have a warning (or less severely, a note) for
 when we infer a polymorphic type that the monomorphism restriction would
 have prevented? That might be useful to pair with
 NoMonomorphismRestriction.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11383#comment:7>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler