Fixes the issue reported at https://github.com/haskell/cabal/issues/4755


and fixes #14304 in the GHC tracker.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: bgamari, austin, goldfire

Reviewed By: bgamari

Subscribers: rwbarton, thomie

GHC Trac Issues: #14304

Differential Revision: https://phabricator.haskell.org/D4057