GHC gives incorrect warnings with simple applications of the view patterns extension
GHC is not able to infer exhaustivity of f1 in the following example
{-# LANGUAGE ViewPatterns #-}
{-# OPTIONS_GHC -fwarn-incomplete-patterns #-}
module VP where
f1, f2 :: Either Int Int -> Either Int Int
f1 (id -> Left _ ) = undefined
f1 (id -> Right _ ) = undefined
f2 (Left _ ) = undefined
f2 (Right _ ) = undefined
f (id -> _) = undefined
GHC outputs:
[1 of 1] Compiling VP ( VP.hs, interpreted )
VP.hs:8:1:
Warning: Pattern match(es) are non-exhaustive
In an equation for `f1': Patterns not matched: _
Ok, modules loaded: VP.I've tested this with GHC 7.0.4, 7.2.2, and 7.4.1-rc1 on Mac OS X.
BTW: There is neither a version entry for 7.2.2 nor for 7.4.1-rc1 in Trac.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 7.3 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |