TH generates ambiguous smart constructors for phantom parameters

[isovector]

The TH currently spits out smart constructors like this:

data Foo e m a where
  FooC :: Foo e m ()

fooC :: forall e r. Member (Foo e) r => Sem r ()
fooC = send FooC

Uh oh! The usage of FooC here is ambiguous! The plugin will correctly determine what it should be (send $ FooC @e), but it'd be nicer if the TH just did the right thing to begin with.

We want to generate this:

fooC :: forall e r. Member (Foo e) r => Sem r ()
fooC = send (FooC @e)

[googleson78]

fooC :: forall e r. Member (Foo e) r => Sem r ()
fooC = send (FooC @e)

is also ambiguous? (according to ghc)

[isovector]

It is, but differently ambiguous! The code as its written today is ambiguous in the effect its trying to send, but the correct code is only ambiguous in terms of AllowAmbiguousTypes :)

[isovector]

Fixed by #67