Crash when using (->) instead of (=>) in a typeclass instance
import qualified Data.Vector as V import Test.QuickCheck import Control.Monad (liftM)
instance (Arbitrary a) -> Arbitrary (V.Vector a) where
arbitrary = fmap V.fromList arbitrary
main = do
print "bla"
The arrow is obviously incorrect.
runghc <thisfile> tells me:
- ** Exception: compiler/rename/RnSource.lhs:429:14-81: Irrefutable pattern failed for pattern Data.Maybe.Just (inst_tyvars,
_,
SrcLoc.L _ cls,
_)
Trac metadata
| Trac field | Value |
|---|---|
| Version | 7.4.1 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler (Parser) |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |