Parsing type constraints in GHC 7.4.1

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,
                                                        _)

>

Trac metadata

Trac field	Value
Version	7.4.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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