#4135: Can't Quote Instance Associated Types in Template Haskell
-------------------------------+--------------------------------------------
Reporter: Ashley Yakeley | Owner:
Type: bug | Status: new
Priority: normal | Component: Template Haskell
Version: 6.12.1 | Keywords:
Os: Linux | Testcase:
Architecture: x86_64 (amd64) | Failure: GHC rejects valid program
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Give this a whirl:
{{{
{-# LANGUAGE TypeFamilies,TemplateHaskell #-}
module Bug where
class C a where
type T a
$([d|
instance C (Maybe a) where
type T (Maybe a) = Char
|])
}}}
{{{
$ ghc -c Bug.hs
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Loading package ffi-1.0 ... linking ... done.
Loading package array-0.3.0.0 ... linking ... done.
Loading package containers-0.3.0.0 ... linking ... done.
Loading package pretty-1.0.1.1 ... linking ... done.
Loading package template-haskell ... linking ... done.
Bug.hs:7:6:
Type indexes must match class instance head
Found `Maybe a[aMy]' but expected `Maybe a[aMx]'
In the associated type instance for `T'
In the instance declaration for `C (Maybe a[aMx])'
[glastonbury:~/Projects/Haskell/Truth/Core]$
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4135>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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