ScopedTypeVariables with nested foralls broken since 8.0.2

The following example fails in 8.2.1 and 8.0.2. Works fine in 7.10.3. If that's intended (that only the first forall has extended scope), I didn't find any mention of that in GHC manual. The two commented out variants work fine in all.

{-# LANGUAGE ScopedTypeVariables #-}

main :: IO ()
main = do
--  let f :: forall a ref. ref () -> ()
--  let f :: forall ref. forall a. ref () -> ()
  let f :: forall a. forall ref. ref () -> ()
      f x = let r :: ref ()
                r = x
            in ()
  return $ f (Just ())

The error (the same in 8.2.1 and 8.0.2) is:

$ ghc --make forall.hs 
[1 of 1] Compiling Main             ( forall.hs, forall.o )

forall.hs:8:21: error:
    • Couldn't match type ‘ref’ with ‘ref1’
      ‘ref’ is a rigid type variable bound by
        the type signature for:
          f :: forall a (ref :: * -> *). ref () -> ()
        at forall.hs:6:29
      ‘ref1’ is a rigid type variable bound by
        the type signature for:
          r :: forall (ref1 :: * -> *). ref1 ()
        at forall.hs:7:22
      Expected type: ref1 ()
        Actual type: ref ()
    • In the expression: x
      In an equation for ‘r’: r = x
      In the expression:
        let
          r :: ref ()
          r = x
        in ()
    • Relevant bindings include
        r :: ref1 () (bound at forall.hs:8:17)
        x :: ref () (bound at forall.hs:7:9)
        f :: ref () -> () (bound at forall.hs:7:7)

Trac metadata

Trac field	Value
Version	8.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
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