[GHC] #14133: COMPLETE pragmas seem to be ignored when using view patterns

[GHC]

#14133: COMPLETE pragmas seem to be ignored when using view patterns
-------------------------------------+-------------------------------------
        Reporter:  jle               |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  error/warning at compile-time      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Description changed by jle:

Old description:

> {{{#!hs
> {-# LANGUAGE ViewPatterns #-}
> {-# LANGUAGE PatternSynonyms #-}
>
> pattern I :: Int -> Int
> pattern I x <- (id -> x)
> {-# COMPLETE I #-}
>
> foo :: Int -> Int
> foo (I x) = x + 3
>
> bar :: Int -> Int
> bar (id->I x) = x + 3
>
> main :: IO ()
> main = return ()
> }}}
>
> Raises a warning for `bar`:
>
> {{{
> Bug.hs:12:1: warning: [-Wincomplete-patterns]
>     Pattern match(es) are non-exhaustive
>     In an equation for 'bar': Patterns not matched: _
>    |
> 12 | bar (id->(I x)) = x + 3
>    | ^^^^^^^^^^^^^^^^^^^^^^^
> }}}
>
> but not for `foo`.

New description:

 {{{#!hs
 {-# LANGUAGE ViewPatterns #-}
 {-# LANGUAGE PatternSynonyms #-}

 pattern I :: Int -> Int
 pattern I x <- (id -> x)
 {-# COMPLETE I #-}

 foo :: Int -> Int
 foo (I x) = x + 3

 bar :: Int -> Int
 bar (id->I x) = x + 3

 main :: IO ()
 main = return ()
 }}}

 Raises a warning for `bar`:

 {{{
 Bug.hs:12:1: warning: [-Wincomplete-patterns]
     Pattern match(es) are non-exhaustive
     In an equation for 'bar': Patterns not matched: _
    |
 12 | bar (id->I x) = x + 3
    | ^^^^^^^^^^^^^^^^^^^^^^^
 }}}

 but not for `foo`.

--

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14133#comment:1>
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