-ddump-deriv doesn't dump failed newtype-deriving

When I say

{-# LANGUAGE GeneralizedNewtypeDeriving, TypeFamilies #-}
{-# OPTIONS_GHC -ddump-deriv #-}

type family F a
type instance F Int = Bool

class C a where
  meth :: a -> F a

instance C Int where
  meth = (> 0)

newtype Age = MkAge Int
  deriving C

I get an error (which I should), but I don't get the derived C instance, as requested by -ddump-deriv. The output should include this helpful information.

Trac metadata

Trac field	Value
Version	7.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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