Can't Quote Instance Associated Types in Template Haskell
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]$
```
<details><summary>Trac metadata</summary>
| Trac field | Value |
| ---------------------- | ---------------- |
| Version | 6.12.1 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Template Haskell |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture | |
</details>
<!-- {"blocked_by":[],"summary":"Can't Quote Instance Associated Types in Template Haskell","status":"New","operating_system":"","component":"Template Haskell","related":[],"milestone":"","resolution":"Unresolved","owner":{"tag":"Unowned"},"version":"6.12.1","keywords":[],"differentials":[],"test_case":"","architecture":"","cc":[""],"type":"Bug","description":"Give this a whirl:\r\n{{{\r\n{-# LANGUAGE TypeFamilies,TemplateHaskell #-}\r\nmodule Bug where\r\n\r\n class C a where\r\n type T a\r\n\r\n $([d| \r\n instance C (Maybe a) where\r\n type T (Maybe a) = Char\r\n |])\r\n}}}\r\n\r\n{{{\r\n$ ghc -c Bug.hs \r\nLoading package ghc-prim ... linking ... done.\r\nLoading package integer-gmp ... linking ... done.\r\nLoading package base ... linking ... done.\r\nLoading package ffi-1.0 ... linking ... done.\r\nLoading package array-0.3.0.0 ... linking ... done.\r\nLoading package containers-0.3.0.0 ... linking ... done.\r\nLoading package pretty-1.0.1.1 ... linking ... done.\r\nLoading package template-haskell ... linking ... done.\r\n\r\nBug.hs:7:6:\r\n Type indexes must match class instance head\r\n Found `Maybe a[aMy]' but expected `Maybe a[aMx]'\r\n In the associated type instance for `T'\r\n In the instance declaration for `C (Maybe a[aMx])'\r\n[glastonbury:~/Projects/Haskell/Truth/Core]$ \r\n}}}","type_of_failure":"OtherFailure","blocking":[]} -->
issue