#1662: mistranslation of arrow notation
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Reporter: ross | Owner: igloo
Type: bug | Status: reopened
Priority: normal | Milestone:
Component: Compiler (Type checker) | Version: 6.8.1
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: arrowrun004, arrowpat | Architecture: Multiple
Os: Multiple |
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Changes (by guest):
* status: closed => reopened
* type: merge => bug
* version: 6.7 => 6.8.1
* resolution: fixed =>
* milestone: 6.8.1 =>
Comment:
As I understand the above {{{TcPat}}} comment, the compiler should not
accept {{{proc}}} expressions with existential constraints. Therefore, I
would expect GHC 6.8.1 to fail on the following code:
{{{
{-# LANGUAGE Arrows, ExistentialQuantification #-}
module ANewPanicWithArrows where
import Control.Arrow
data T = forall a. T a
panic :: (Arrow arrow) => arrow T T
panic = proc (T x) -> do returnA -< T x
}}}
However, as the code suggests, GHC doesn’t fail but panics again:
{{{
ghc-6.8.1: panic! (the 'impossible' happened)
(GHC version 6.8.1 for i386-unknown-linux):
initC: srt_lbl
}}}
If I load the module into GHCi, GHCi doesn’t complain, but it panics with
{{{nameModule arr{v apv}}}} (instead of {{{initC: srt_lbl}}}) when I start
to use the {{{panic}}} arrow.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1662#comment:10>
GHC <http://www.haskell.org/ghc/>
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