New dict implementation

[Skinney]

A new Dict implementation based on Left-Leaning Red-Black trees (LLRB). Performance numbers can be found here: https://discourse.elm-lang.org/t/new-dict-implementation-for-elm-now-done/174/3

The code that is commented out helps validating the invariants of a LLRB tree. It's not something that should be built in production builds, or even used by regular users, but it's invaluable when making changes to the data structure.

[process-bot]

Thanks for the pull request! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[process-bot]

Thanks for the pull request! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[Skinney]

Just wanted to mention @justinmimbs, who did some impressive work on this code.

[Skinney]

Just wanted to mention @justinmimbs, who did some impressive work on this code.

[evancz]

Do you mind getting the conflicts resolved? I think we should try to see the impact on code size in applications that use dictionaries!

[evancz]

Do you mind getting the conflicts resolved? I think we should try to see the impact on code size in applications that use dictionaries!

[evancz]

I think messy commits are kind of lame, so if it is easier, just close and open a new PR with just the changes in a commit or something. Or not. Whatever works!

[evancz]

I think messy commits are kind of lame, so if it is easier, just close and open a new PR with just the changes in a commit or something. Or not. Whatever works!