Set.difference arguments disagree in SDK vs dev_compiler (Set<E> vs Set<Object>)

[kevmoo]

Hit this trying to compile pkg/collection w/ DDC.

Help?

CC @vsmenon @leafpetersen

The dev_compiler version was updated on March 5, 2015 (to Set, which is good)
SDK version hasn't been changed since Mar 13, 2013

[floitschG]

The core library's version looks fine to me. I don't know why DDC has Set<E>.

Somehow related: why does api.dartlang.org not show Set<Object>? https://api.dartlang.org/stable/1.20.0/dart-core/Set/difference.html

[kevmoo]

No! The SDK has Set<E> – DDC has (the correct version, IMHO) Set<Object>

[lrhn]

It probably should have been Set<Object> for symmetry with intersection and similarity with removeAll.
Changing it now will be a breaking change for strong mode - that makes all existing implementations have covariant parameter overrides which isn't strong-mode sound.

[kevmoo]

Changing it now will be a breaking change for strong mode

Ironically, DDC (at least for its copy of the SDK) is already shipping the break 😄

[floitschG]

Aah. I looked at the wrong place.
The SetMixin has Set<Object>. (This is probably the reason that DDC has it fixed).
This is just a mistake in the interface.

[vsmenon]

What do you guys think is the right fix?

[floitschG]

It should be safe to change Set in the core library.

[lrhn]

Agree, if all the existing implementations have the other behavior anyway, and they do if the use SetBase or SetMixin, then we should just fix the interface.

[vsmenon]

Sounds like package:collection will need to be fixed as well from @kevmoo 's original message.