hackport uses := slot operator under '||' dep clause.

[crocket]

  dependency.badslotop [fatal]  4
   dev-haskell/cabal-helper/cabal-helper-0.8.2.0.ebuild: RDEPEND: '>=dev-haskell/cabal-1.14:=[profile?]' uses ':=' slot operator under '||' dep clause.
   dev-haskell/cabal-helper/cabal-helper-0.8.2.0.ebuild: RDEPEND: '<dev-haskell/cabal-1.26:=[profile?]' uses ':=' slot operator under '||' dep clause.
   dev-haskell/cabal-helper/cabal-helper-0.8.2.0.ebuild: RDEPEND: '>=dev-haskell/cabal-2.0:=[profile?]' uses ':=' slot operator under '||' dep clause.
   dev-haskell/cabal-helper/cabal-helper-0.8.2.0.ebuild: RDEPEND: '<dev-haskell/cabal-2.5:=[profile?]' uses ':=' slot operator under '||' dep clause.

[trofi]

The workaround is to manually edit the generated constraints in a ebuild. I usually pick larger version range if appropriate. But it's hard to implement in a generic way.

[crocket]

I manually removed := to work around the issue.

[trofi]

Removal of := is usually not correct as it inhibits package rebuild after cabal update.