#5990: Malformed instance declaration produces panic
--------------------------------+-------------------------------------------
Reporter: ChrisN | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler (Parser)
Version: 7.5 | Keywords: malformed instance , pars,
renamer, RnSource
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Compile-time crash | Testcase:
Blockedby: | Blocking:
Related: |
--------------------------------+-------------------------------------------
The following code produces a panic with 7.5:
{{{
module Test where
class F a b where
f :: a b Int
instance F -> b where
f _ = 1
}}}
whereas this code works as expected:
{{{
{-# LANGUAGE MultiParamTypeClasses , FlexibleInstances#-}
module Test where
class F a b where
f :: a b Int
instance F (->) b where
f _ = 1
}}}
GHC 7.2.2 correctly identifies this as a malformed instance header.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5990>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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