[GHC] #9497: Silent typed holes

[GHC]

#9497: Silent typed holes
-------------------------------------+-------------------------------------
       Reporter:  merijn             |                   Owner:
           Type:  feature request    |                  Status:  new
       Priority:  normal             |               Milestone:
      Component:  Compiler           |                 Version:  7.8.3
       Keywords:  typed holes,       |        Operating System:
  warnings                           |  Unknown/Multiple
   Architecture:  Unknown/Multiple   |         Type of failure:
     Difficulty:  Unknown            |  None/Unknown
     Blocked By:                     |               Test Case:
Related Tickets:                     |                Blocking:
                                     |  Differential Revisions:
-------------------------------------+-------------------------------------
 I have a UI feature request for -fwarn-typed-holes, currently there's two
 options: 1) typed holes are on (default) and GHC prints errors for types
 holes or 2) typed holes are off and GHC will print "not in scope" error
 and prematurely end compilation.

 When writing haskell, I frequently want to typecheck my code before it's
 completely implemented. Before I used undefined/error, which worked but I
 was always worried about accidentally forgetting an undefined somewhere.
 With typed holes this is no longer a problem, but unfortunately the
 warnings from typed holes are so verbose they drown out the other type
 errors. This makes typechecking during refactoring rather onerous.

 I propose adding a -fsilent-typed-holes and/or -ftreat-type-holes-as-
 undefined which enable typed holes, but silence any compile time warnings.
 It'd be nice if this flag treated holes as if "-fdefer-type-errors" was
 on, but ONLY for typed holes.

 This would let me compile the code and fix warnings, ignoring the holes
 while developing, while still assuring that, when I remove the flag and
 compile "for real" I get an error about typed holes.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9497>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler