Regression: can't export constructor when conflicting, qualified constructor is also in scope

I ran into this regression when trying to compile the ersatz library with GHC 8.2.1-rc1. Here is a minimized example:

module Bug (Bits(Bits)) where

import qualified Data.Bits as Bits

newtype Bits = Bits Int

Compiling this with GHC 8.0.2 works fine, but with 8.2.1-rc1, you get this error:

l$ /opt/ghc/8.2.1/bin/ghci Bug.hs
GHCi, version 8.2.0.20170422: http://www.haskell.org/ghc/  :? for help
Loaded GHCi configuration from /home/rgscott/.ghci
[1 of 1] Compiling Bug              ( Bug.hs, interpreted )

Bug.hs:1:13: error:
    • Ambiguous occurrence ‘Bits’
      It could refer to either ‘Bits.Bits’,
                               imported qualified from ‘Data.Bits’ at Bug.hs:3:1-34
                            or ‘Bits’, defined at Bug.hs:5:1
    • In the export: Bits(Bits)
  |
1 | module Bug (Bits(Bits)) where
  |             ^^^^^^^^^^

Despite the fact that Bits isn't actually ambiguous, since the Bits from Data.Bits is qualified.

Trac metadata

Trac field	Value
Version	8.2.1-rc2
Type	Bug
TypeOfFailure	OtherFailure
Priority	high
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	mpickering
Operating system
Architecture