rfc: preflight type reflection

[Chriscbr]

Related to #4106

Proposal for an extension to Winglang that adds support for type reflection. Examples and an implementation sketch is included.

Checklist

• Title matches Winglang's style guide
• Description explains motivation and solution
• Tests added (always)
• Docs updated (only required for features)
• Added pr/e2e-full label if this feature requires end-to-end testing

By submitting this pull request, I confirm that my contribution is made under the terms of the Wing Cloud Contribution License.

[github-actions]

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Topic	Owner
Wing SDK and standard library	@chriscbr
Wing Console	@skyrpex
Wing compiler and language design	@chriscbr
VSCode extension and language server	@chriscbr
Wing CLI	@chriscbr
Documentation	@boyney123
Examples	@boyney123
Wing Playground	@skyrpex

[eladb]

Beautiful! No comments! Ship it!

[mergify]

Thanks for contributing, @Chriscbr! This PR will now be added to the merge queue, or immediately merged if rybickic/type-reflection is up-to-date with main and the queue is empty.

[Chriscbr]

@eladb An extra note...

There's really two kinds of reflection that we could imagine supporting.

In the examples I've shown in the RFC, a specific type is always given to the function. This is pretty powerful, as the examples show. It's less risky to implement since the Type value that's returned is known by the time the JavaScript is generated.

But one could imagine a more powerful reflection macro that lets you pass an arbitrary value/variable. (It could be a separate macro like @typeOf(...), or it could be part of the same macro). I think this macro would be more tricky to implement since it could requires more cross-cutting changes to our code generation (say, by annotating preflight values with type info via hidden properties or something like that...), though it would be mighty cool.

[monadabot]

Congrats! 🚀 This was released in Wing 0.85.12.