#6051: Parsing type constraints in GHC 7.4.1
-----------------------------------------------+----------------------------
Reporter: leepike | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.4.1 | Keywords:
Os: Linux | Architecture:
Unknown/Multiple
Failure: Incorrect warning at compile-time | Testcase:
Blockedby: | Blocking:
Related: |
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This appears to be a parsing bug, or at least a bad error message, for a
*malformed* type constraint:
Given the following malformed program, I get the following output loading
it with ghci (GHC 7.4.1):
------------------------------------
{{{
module Test where
data Foo a = Foo a
-- Malformed!
instance Ord a => Eq a => Show (Foo a) where
show (Foo a) = undefined
}}}
-------------------------------------
{{{
$ ghci Test.hs
GHCi, version 7.4.1: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling Test ( Test.hs, interpreted )
*** Exception: compiler/rename/RnSource.lhs:429:14-81: Irrefutable pattern
failed for pattern Data.Maybe.Just (inst_tyvars,
_,
SrcLoc.L _ cls,
_)
>
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6051>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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