[GHC] #14917: Allow levity polymorhism in binding position

[GHC]

#14917: Allow levity polymorhism in binding position
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        Reporter:  andrewthad        |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:
                                     |  LevityPolymorphism
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 I'm very cautious about this.

 Sometimes you can't inline.  For example a recursive function.  And
 {{{
 f :: Int -> Int
 {-# INLINE f #-}
 f x = blah

 g xs = map f xs
 }}}
 I can't inline `f` here; or if I do I'll get a `\x`.

 In our paper we prove that, in our system, you never get a situation where
 you don't know the runtime reprsentation of a value you have to
 manipulate.  I don't see how to produce a similar proof with weaker
 restrictions.

 Runtime code cloining, like .NET, is a good path.  But it comes at a
 price!

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14917#comment:1>
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