[GHC] #10896: BadSock triggers failing ASSERT

[GHC]

#10896: BadSock triggers failing ASSERT
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        Reporter:  ezyang            |                Owner:
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  7.11
  checker)                           |
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:  indexed-
                                     |  types/should_fail/BadSock
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D1260
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"1e041b7382b6aa329e4ad9625439f811e0f27232/ghc"
 1e041b73/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="1e041b7382b6aa329e4ad9625439f811e0f27232"
 Refactor treatment of wildcards

 This patch began as a modest refactoring of HsType and friends, to
 clarify and tidy up exactly where quantification takes place in types.
 Although initially driven by making the implementation of wildcards more
 tidy (and fixing a number of bugs), I gradually got drawn into a pretty
 big process, which I've been doing on and off for quite a long time.

 There is one compiler performance regression as a result of all
 this, in perf/compiler/T3064.  I still need to look into that.

 * The principal driving change is described in Note [HsType binders]
   in HsType.  Well worth reading!

 * Those data type changes drive almost everything else.  In particular
   we now statically know where

        (a) implicit quantification only (LHsSigType),
            e.g. in instance declaratios and SPECIALISE signatures

        (b) implicit quantification and wildcards (LHsSigWcType)
            can appear, e.g. in function type signatures

 * As part of this change, HsForAllTy is (a) simplified (no wildcards)
   and (b) split into HsForAllTy and HsQualTy.  The two contructors
   appear when and only when the correponding user-level construct
   appears.  Again see Note [HsType binders].

   HsExplicitFlag disappears altogether.

 * Other simplifications

      - ExprWithTySig no longer needs an ExprWithTySigOut variant

      - TypeSig no longer needs a PostRn name [name] field
        for wildcards

      - PatSynSig records a LHsSigType rather than the decomposed
        pieces

      - The mysterious 'GenericSig' is now 'ClassOpSig'

 * Renamed LHsTyVarBndrs to LHsQTyVars

 * There are some uninteresting knock-on changes in Haddock,
   because of the HsSyn changes

 I also did a bunch of loosely-related changes:

 * We already had type synonyms CoercionN/CoercionR for nominal and
   representational coercions.  I've added similar treatment for

       TcCoercionN/TcCoercionR

       mkWpCastN/mkWpCastN

   All just type synonyms but jolly useful.

 * I record-ised ForeignImport and ForeignExport

 * I improved the (poor) fix to Trac #10896, by making
   TcTyClsDecls.checkValidTyCl recover from errors, but adding a
   harmless, abstract TyCon to the envt if so.

 * I did some significant refactoring in RnEnv.lookupSubBndrOcc,
   for reasons that I have (embarrassingly) now totally forgotten.
   It had to do with something to do with import and export

 Updates haddock submodule.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10896#comment:8>
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