[GHC] #11786: Need -fno-print-explicit-runtime-reps to work on IfaceType, else RuntimeRep leaks

[GHC]

#11786: Need -fno-print-explicit-runtime-reps to work on IfaceType, else RuntimeRep
leaks
-------------------------------------+-------------------------------------
        Reporter:  simonpj           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
                                     |  LevityPolymorphism
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13275, #15181    |  Differential Rev(s):  Phab:D4733
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by simonpj):

 Yikes.  I have just wasted 30 minutes (in Core dumps) figuring out why a
 type printed as
 {{{
 forall a b. Eq a => blah
 }}}
 didn't match a term
 {{{
 /\ a. \(d :: Eq a). blah
 }}}
 Turns out that the real type is `forall a. Eq a => forall b. blah`, but
 the pretty printer silently moves the foralls to the top.  This is done in
 `splitIfaceSigmaTy` in the patch in comment:13.

 It might be ''just'' arguable to move the foralls around for ''user''
 types.  E.g in test `ghci025` we now report
 {{{
 return :: Monad m => a -> m a
 }}}
 whereas previously it was
 {{{
 return :: Monad m => forall a. a -> m a
 }}}
 But we definitely should not do this in Core printouts.

 I also noticed that in the output for `ghci025` we have
 {{{
 c3 :: forall a b a. C a b => a -> b
 }}}
 The repeated 'a' is terrible!

 So I'm re-opening this ticket to ask: do we want to swizzle the foralls to
 the top, even  in user printout?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11786#comment:16>
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