[GHC] #14609: Per-instance UndecidableInstances

[GHC]

#14609: Per-instance UndecidableInstances
-------------------------------------+-------------------------------------
           Reporter:  ryanreich      |             Owner:  (none)
               Type:  feature        |            Status:  new
  request                            |
           Priority:  low            |         Milestone:
          Component:  Compiler       |           Version:  8.2.2
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 The LANGUAGE pragma OverlappingInstances is now a per-instance modifier
 specifying the manner of overlap.  Can (or why can't) this also be done
 for UndecidableInstances?  It gives me an icky feeling to put it at the
 top of a source file when I just want to allow one specific instance to be
 undecidable.

 My apologies if this request already exists.  It is very difficult to find
 bugs about UndecidableInstances in particular as opposed merely to those
 containing code with this pragma, which appear to be numerous.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14609>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler