Deferred block doesn't unify abilities list when it should.

[ChrisPenner]

unique type AbilityHolder g =
  AbilityHolder ('{g} ())


fails : AbilityHolder {Stream Nat}
fails = AbilityHolder (forever' do
  ()
  )

works : AbilityHolder {Stream Nat}
works = AbilityHolder (do
  ()
  )


alsoWorks : AbilityHolder {Stream Nat}
alsoWorks = AbilityHolder (forever' do
  emit 1
  )

It seems that something about forever' : '{g} a -> '{g} b is throwing off ability inference so that it doesn't allow the empty ability list to unify with an unused ability.

If I actually use the expected ability it works fine 🤷🏼