Source generator proposal: Equality

[333fred]

We should consider building and shipping a source generator for equality as part of the default .NET tooling. The C# LDT has explicitly backed off from doing a completely-customizable equality feature: https://github.com/dotnet/csharplang/blob/master/meetings/2020/LDM-2020-03-30.md#value-equality. However, it seems like customizable equality (such as sequence equality for collections, case-insensitive comparison for strings, other customizations) are and will continue to be a pain point. We should consider building a first-party generator for equality, with annotation types built into the framework and the generator shipped with the SDK. If we don't do this with the initial release of source-generators or soon afterwards, we may end up with a fractured ecosystem of such generators with no consistent style.

/cc @chsienki

[Jose10go]

Sorry for write here but ... is there a place for a join a discussion on allow edition in source generation and ideas to make the edition "save". I cant find it ... sorry again

[jmarolf]

@Jose10go being able to modify existing code is not a feature we anticipate ever doing at this time. Please file a new issue on this repo if you want to discuss it.

[333fred]

Moving this to the runtime repo, as this would be an in-box source generator.

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[carlossanlop]

@danmoseley is the code-analyzer label correct?

[danmoseley]

No, fixed.

[CyrusNajmabadi]

Assigning to myself to proceed with a WG to come up with a proposal here. TAgging @cston @333fred @RikkiGibson @jcouv who all showed interest in this topic.

Related to dotnet/roslyn#48646.