Template Haskell quotes of data instance GADTs is totally broken

When I say

data family Fuggle x y
[d| data instance Fuggle Int (Maybe (a,b)) where
      MkFuggle :: Fuggle Int (Maybe Bool) |]

I get (with -ddump-splices)

    [d| data instance Fuggle Int (Maybe (a_ajz6, b_ajz7))
          where MkFuggle_ajz5 :: Fuggle Int (Maybe Bool) |]
  ======>
    data instance Fuggle Int (Maybe (a_ajAf, b_ajAg))
      = (b_ajAg ~ Maybe Bool, a_ajAf ~ Int) => MkFuggle_ajAe

But that's not at all what I said! Admittedly, what I said was garbage, but it should fail outright.

Is this addressed by D1465?

Trac metadata

Trac field	Value
Version	7.10.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Template Haskell
Test case
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CC	jstolarek
Operating system
Architecture