[GHC] #7855: Use optimizer for more information about incomplete pattern matches

[GHC]

#7855: Use optimizer for more information about incomplete pattern matches
----------------------------------------+-----------------------------------
    Reporter:  ezyang                   |       Owner:                  
        Type:  feature request          |      Status:  new             
    Priority:  normal                   |   Milestone:                  
   Component:  Compiler (Type checker)  |     Version:  7.7             
    Keywords:                           |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple         |     Failure:  None/Unknown    
  Difficulty:  Unknown                  |    Testcase:                  
   Blockedby:                           |    Blocking:                  
     Related:                           |  
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Changes (by igloo):

  * difficulty:  => Unknown


Comment:

 This sounds fragile to me. e.g. whether this:
 {{{
 module M (f) where

 f :: Int -> ()
 f x = g True

 g :: Bool -> ()
 g True = ()
 }}}
 gives a warning would depend on whether g gets inlined and discarded. This
 could mean that a small change to the source could make dozens of warnings
 appear in seemingly unrelated functions.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7855#comment:1>
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