[GHC] #12660: singletons doesn't compile with GHC 8.0.2 snapshot

[GHC]

#12660: singletons doesn't compile with GHC 8.0.2 snapshot
-------------------------------------+-------------------------------------
        Reporter:  bgamari           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.2
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

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

 In [changeset:"8fa5f5b197542b6e7e9e570991a1488204e606c9/ghc"
 8fa5f5b1/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="8fa5f5b197542b6e7e9e570991a1488204e606c9"
 Add derived shadows only for Wanted constraints

 This patch implements choice (3) of comment:14 on Trac #12660.
 It cures an infinite loop (caused by the creation of an infinite
 type) in in compiling the 'singletons' package.

 See Note [Add derived shadows only for Wanteds] in TcSMonad.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12660#comment:15>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler