[GHC] #10615: Panic; no skolem info (partial type signatures)

[GHC]

#10615: Panic; no skolem info (partial type signatures)
-------------------------------------+-------------------------------------
              Reporter:  holzensp    |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.10.1
              Keywords:              |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  None/Unknown
  Unknown/Multiple                   |        Blocked By:
             Test Case:              |   Related Tickets:
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------
 This rather minimal program
 {{{#!hs
 f :: _ => _f
 f = const
 }}}
 results in this:
 {{{
 GHCi, version 7.10.1: http://www.haskell.org/ghc/  :? for help
 [1 of 1] Compiling Main             ( Panic.hs, interpreted )

 Panic.hs:1:6:
     Found hole ‘_’ with inferred constraints: ()
     To use the inferred type, enable PartialTypeSignatures
     In the type signature for ‘f’: _ => _f

 Panic.hs:2:5:
     Couldn't match expected type ‘_f’ with actual type ‘a0 -> b0 -> a0’
       ‘_f’ is untouchable
         inside the constraints ()
         bound by the inferred type of f :: _f
         at Panic.hs:2:1-9ghc: panic! (the 'impossible' happened)
   (GHC version 7.10.1 for x86_64-apple-darwin):
         No skolem info: _f_alF[sk]
 }}}

 The newest open bugs (that reporter could find at the time of reporting)
 with "no skolem info" in their description are #10404 and #10432. The
 newest bug (which is closed) is #10503. It seems likely, though, that the
 above comes from the PartialTypeSignatures implementation (considering the
 simplicity of the repro).

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10615>
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