[GHC] #8477: Allow inferring ambiguous types

[GHC]

#8477: Allow inferring ambiguous types
------------------------------------+-------------------------------------
       Reporter:  aavogt            |             Owner:
           Type:  feature request   |            Status:  new
       Priority:  normal            |         Milestone:
      Component:  Compiler          |           Version:  7.6.3
       Keywords:                    |  Operating System:  Unknown/Multiple
   Architecture:  Unknown/Multiple  |   Type of failure:  None/Unknown
     Difficulty:  Unknown           |         Test Case:
     Blocked By:                    |          Blocking:
Related Tickets:  8390              |
------------------------------------+-------------------------------------
 Previous versions of ghc could infer types that are potentially ambiguous.
 This allowed things like http://okmij.org/ftp/Haskell/TypeLambdaVal.hs or
 assigning keyword args functions to variables
 http://code.haskell.org/~aavogt/HList/docs/HList/Data-HList-Keyword.html.
 Presently (7.6 and 7.7), you need to write a type signature yourself to
 allow such definitions, which in these situations doubles the amount of
 code to write. For the keyword case, the workaround is to use the kw
 function to apply the keyword function instead of ordinary function
 application.

 More related discussion http://www.haskell.org/pipermail/glasgow-haskell-
 users/2013-October/024404.html

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8477>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler