[GHC] #12466: Typechecker regression: Inaccessible code in a type expected by the context

[GHC]

#12466: Typechecker regression: Inaccessible code in a type expected by the context
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler (Type    |              Version:  8.1
  checker)                           |
      Resolution:                    |             Keywords:
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:                    |
-------------------------------------+-------------------------------------

Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"03541cbae50f0d1cdf99120ab88698f29a278159/ghc"
 03541cba/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="03541cbae50f0d1cdf99120ab88698f29a278159"
 Be less picky about reporing inaccessible code

 Triggered by the discussion on Trac #12466, this patch
 makes GHC less aggressive about reporting an error when
 there are insoluble Givens.

 Being so agressive was making some libraries fail to
 compile, and is arguably wrong in at least some cases.
 See the discussion on the ticket.

 Several test now pass when they failed before; see
 the files-modified list for this patch.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12466#comment:37>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler