[GHC] #13413: GHC HEAD panic: collectNBinders

[GHC]

#13413: GHC HEAD panic: collectNBinders
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        Reporter:  RyanGlScott       |                Owner:  simonpj
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:  JoinPoints
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"a7dbafe9292212f3cbc21be42eb326ab0701db7e/ghc" a7dbafe/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="a7dbafe9292212f3cbc21be42eb326ab0701db7e"
 No join-point from an INLINE function with wrong arity

 The main payload of this patch is NOT to make a join-point
 from a function with an INLINE pragma and the wrong arity;
 see Note [Join points and INLINE pragmas] in CoreOpt.
 This is what caused Trac #13413.

 But we must do the exact same thing in simpleOptExpr,
 which drove me to the following refactoring:

 * Move simpleOptExpr and simpleOptPgm from CoreSubst to a new
   module CoreOpt along with a few others (exprIsConApp_maybe,
   pushCoArg, etc)

   This eliminates a module loop altogether (delete
   CoreArity.hs-boot), and stops CoreSubst getting too huge.

 * Rename Simplify.matchOrConvertToJoinPoint
      to joinPointBinding_maybe
   Move it to the new CoreOpt
   Use it in simpleOptExpr as well as in Simplify

 * Define CoreArity.joinRhsArity and use it
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13413#comment:4>
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