Implement with instance chains

[garyb]

I think as per #9 we probably want to deprecate this library and put these classes with Either/Coproduct, but just thought I'd try this out.

@LiamGoodacre I was a little surprised to find that it didn't raise an error even when these were defined without instance chains until used. I thought purescript/purescript#3129 would have changed that? Maybe I misunderstood.

[LiamGoodacre]

Ooooh, I will have a play tomorrow and see if I messed something up. Thanks!

[LiamGoodacre]

Should be Data.Inject.Coproduct?

[garyb]

Uh yes 😉

[chexxor]

Yeah, this change is required to compile - it collides with the other Data.Inject.Either module in this project.

[LiamGoodacre]

Are you sure you were building with latest master?
Without instance chains I get:

    Overlapping type class instances found for

      Main.Inject f
                  (Coproduct f g)

    The following instances were found:

      Main.injectReflexive
      Main.injectLeft

[LiamGoodacre]

(The error says Main. because I copied the definitions into an example project.)

[garyb]

Ack, maybe it was user error on my part then... I did pull master and stack install for sure, but maybe I still did something wrong in there / it was using the wrong PATH or something.

The other thing I thought of, is this version using instance chains can inject into the left or the right, the original definition is biased to one side, so perhaps I tested with that and it failed. I'll try and reproduce again later today, sorry to waste your time!

[garyb]

@LiamGoodacre I figured it out. I did git pull master but not git pull purescript master 🤦‍♂️

[chexxor]

Requires a few changes to compile with the 0.12 package-set.

[chexxor]

id => identity

[chexxor]

Yeah, this change is required to compile - it collides with the other Data.Inject.Either module in this project.

[chexxor]

id => identity

[chexxor]

Requested changes are addressed in #11, so you can merge that, then merge this PR later.

[LiamGoodacre]

Closing as we will move these type classes and instances to functors/either.