singletons broken by Quick Look

head.hackage suggests that singletons no longer builds with master.

src/Data/Singletons/Sigma.hs:61:10: error:
    * Expected kind `k0',
        but `Sigma' has kind `forall s -> (s ~> *) -> *'
      Cannot instantiate unification variable `k0'
      with a kind involving polytypes: forall s -> (s ~> *) -> *
    * In the type `Sigma'
      In the type declaration for `?'
   |
61 | type ? = Sigma
   |          ^^^^^
cabal: Failed to build singletons-2.6 (which is required by
test-singletons-1.0). See the build log above for details.

This change seems to be correlated with the merge of Quick Look.