[GHC] #10315: ApiAnnotations : Empty context loses annotations

[GHC]

#10315: ApiAnnotations : Empty context loses annotations
-------------------------------------+-------------------------------------
              Reporter:  alanz       |             Owner:  alanz
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:  7.10.2
             Component:  Compiler    |           Version:  7.10.1
              Keywords:              |  Operating System:  Unknown/Multiple
  ApiAnnotations                     |   Type of failure:  None/Unknown
          Architecture:              |        Blocked By:
  Unknown/Multiple                   |   Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------
 A type signature of the form

 {{{#!hs
 bar :: (   ) => a-> Bool
 }}}

 generates annotations for the `(  ) =>` but the SrcSpan they are attached
 to is discarded so the annotations are not attached to the AST.

 The discarding process happens in

 {{{#!hs
 mkHsForAllTy exp tvs (L _ []) ty = mk_forall_ty exp tvs ty
 }}}

 where the empty located context is discarded.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10315>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler