Why is this HasField instance not being resolved?

I'm using GHC 8.2.1. I have the following module:

{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE ScopedTypeVariables #-}
module Moat (Moat,moat) where

import GHC.Records (HasField(..))

newtype Moat r = Moat r

moat :: r -> Moat r
moat = Moat

instance HasField s r v => HasField s (Moat r) v where
    getField (Moat r) = getField @s r

And this other one:

module Foo (Foo(..)) where

data Foo a = Foo { getDims :: (Int, Int), getData :: [a] }

My problem is that when I have both modules imported and I try to do something like:

{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE DataKinds #-}
import Moat
import Foo
import GHC.Records

oops :: (Int,Int)
oops = getField @"getDims" (moat (Foo (5,5) ['c']))

I get this error:

No instance for (HasField "getDims" (Moat (Foo Char)) (Int, Int))
       arising from a use of ‘getField’

Why is the HasField instance not being resolved?