Allow JS functions to be directly added to via `table.set`?

[sbc100]

See WebAssembly/design#1408

I wonder if we can add this to this proposal. It not only avoids having to use the WebAssembly.Function API everywhere but its more flexible because it means we don't need to know ahead of time the signature of the function being implemented in JS and it allows us to take advantage of JS polymorphism in the same way we already can for imports.

[SPY]

I believe this proposal doesn't suite a suggested change.
JS Types Reflection is focused on getting data from Wasm to JS and for that purpose WebAssembly.Function is introduced as a missing piece for type() method.
The fact WebAssembly.Function opens a possibility for setting JS functions to WebAssembly.Tables without creating a temporary module is a convenience bonus, but not a purpose of this proposal.

[sbc100]

Closing this for now. We can continue to discuss this in WebAssembly/design#1408