unison/unison-src/transcripts/ability-term-conflicts-on-update.md

Regression test for updates which conflict with an existing ability constructor

https://github.com/unisonweb/unison/issues/2786

scratch/main> builtins.merge lib.builtins

First we add an ability to the codebase. Note that this will create the name Channels.send as an ability constructor.

unique ability Channels where
  send : a -> {Channels} ()

scratch/main> add

Now we update the ability, changing the name of the constructor, but, we simultaneously add a new top-level term with the same name as the constructor which is being removed from Channels.

unique ability Channels where
  sends : [a] -> {Channels} ()

Channels.send : a -> ()
Channels.send a = ()

thing : '{Channels} ()
thing _ = send 1

These should fail with a term/ctor conflict since we exclude the ability from the update.

scratch/main> update.old patch Channels.send
scratch/main> update.old patch thing

If however, Channels.send and thing depend on Channels, updating them should succeed since it pulls in the ability as a dependency.

unique ability Channels where
  sends : [a] -> {Channels} ()

Channels.send : a -> ()
Channels.send a = sends [a]

thing : '{Channels} ()
thing _ = send 1

These updates should succeed since Channels is a dependency.

scratch/main> update.old.preview patch Channels.send
scratch/main> update.old.preview patch thing

We should also be able to successfully update the whole thing.

scratch/main> update.old

Constructor-term conflict

scratch/main2> builtins.merge lib.builtins

X.x = 1

scratch/main2> add

structural ability X where
  x : ()

This should fail with a ctor/term conflict.

scratch/main2> add