Add the initial draft for inference-using-bounds

[chloestefantsova]

This PR adds the initial draft for the inference-using-bounds language feature specification.

[stereotype441]

lgtm, but since I'm relatively inexperienced in writing specs, I'm going to tag in @eernstg as another reviewer

[kevmoo]

Cool to see the inline mermaid!

[eernstg]

Looks good!

I think the actual feature specification is the modification of 'inference.md', and the other document is all about background and motivation.

So I'm suggesting that feature-specification.md is renamed (perhaps to design-document.md).

With this rename in place, it's perfectly fine that the document doesn't specify the precise rules, and that it is completely example-driven.

I do suggest, though, that the formal update (that is, the new text in inference.md) is mentioned up front in the design document, such that (1) readers will still know what the diff is without needing to track down the git update where inference.md was updated, and (2) the design document is explicit about the precise thing that it's motivating and explaining. This would just be a short section.

[eernstg]

Let me just do LGTM, to make sure I am not blocking anything.

[sgrekhov]

Github doesn't allow to comment that line, so I'm writing it here. File inference.md, informal section on lines L745-746.

The bound of a type variable is only included as a constraint when the
choice of type for that type variable is about to be frozen.

Seems that it should be updated as well.

[chloestefantsova]

Github doesn't allow to comment that line, so I'm writing it here. File inference.md, informal section on lines L745-746.

The bound of a type variable is only included as a constraint when the
choice of type for that type variable is about to be frozen.

Seems that it should be updated as well.

Thanks for spotting that! The informal section should be updated, tool.

[eernstg]

LGTM!

[chloestefantsova]

Thanks for the review and the comments, everybody!

[Kutter07]

(accepted/future-releases/3009-inference-using-bounds/design-document.md )+
(resources/type-system/inference.md)