Change MapSet.t definition to make Dialyzer happy

[michallepicki]

I hate to bring this issue up again, but it's still causing friction, see elixirforum thread

I think with this change, the only disadvantage is that the field will need to be named map even if the internal implementation changes? I don't know if changing it to something more general would be considered a breaking change or not.

[josevalim]

💚 💙 💜 💛 ❤️

[michallepicki]

Thank you for allowing for this compromise! I know it's not ideal and doesn't anticipate other fields in the top-level struct, but hopefully it won't hurt performance with any potential changes in the future

[bmitc]

Thank you for the fix @michallepicki and thanks for merging this in @josevalim! This is great since it gets rid of both pattern_match and opaque_match Dialyzer errors when pattern matching against %MapSet{}. 👍

Is the Elixir version this will be included in going to be 1.14?

[josevalim]

Yes!