[GHC] #13256: Warn on out-of-range literals in pattern matches too

9 Feb 2017


      #13256: Warn on out-of-range literals in pattern matches too
-------------------------------------+-------------------------------------
           Reporter:  rwbarton       |             Owner:
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.1
           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:
-------------------------------------+-------------------------------------
 We have these nice warnings for numeric literal expressions that are out
 of range of their type:
 {{{
 Prelude> 100000000000000000000000000000000 :: Int

 <interactive>:1:1: warning: [-Woverflowed-literals]
     Literal 100000000000000000000000000000000 is out of the Int range
 -9223372036854775808..9223372036854775807
 }}}
 but nothing for numeric patterns:
 {{{
 Prelude> (\x -> case (x :: Int) of 100000000000000000000000000000000 -> 0)
 8 :: Int

 <interactive>:3:8: warning: [-Wincomplete-patterns]
     Pattern match(es) are non-exhaustive
     In a case alternative:
         Patterns not matched:
             p where p is not one of {100000000000000000000000000000000}
 *** Exception: <interactive>:3:8-64: Non-exhaustive patterns in case
 }}}

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13256
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler