Multibindings support

[badoualy]

Not sure if this is something that should be done, maybe it's going too far.

Support for multibindings could be interesting
Equivalent of IntoMap or IntoSet

eg:

@BoundIntoMap(component = ..., supertype = ...)
class Foo @Inject constructor(): Bar

[sczerwinski]

This would be a reasonable feature.

While adding support for @IntoSet and @ElementsIntoSet would be pretty straightforward, I'm not sure how to provide keys for @IntoMap. There are: @StringKey, @ClassKey and any custom annotation annotated with @MapKey (I can see reasonable solution for the first two).

Also, currently, there are 6 annotations:

• @Bound
• @BoundTo
• @FactoryMethod
• @TestBound
• @TestBoundTo
• @TestFactoryMethod
  so instead of creating additional 3+ variants of each, I'd rather define parameter(s) in existing ones.

I'll need some time to think it though. As always, any suggestions are welcome.

[sczerwinski]

I still haven't figured out a nice way to do it. But I'm open to any suggestions/pull requests.

Moving the issue to discussions.