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 |