Go To Definition should go to Deconstruct() in deconstructing assignments

[SLaks]

When I press F12 on the = token in (a, b) = blah (where blah has a Deconstruct()), can you open the Deconstruct() method?

Just like F12 already opens operator overloads.

This would help people understand how tuples work in general, and would be quite helpful when navigating an unfamiliar codebase that uses custom deconstructable types.

[CyrusNajmabadi]

I might broaden this to include any sort of explicit conversion. It's a nice idea.

[SLaks]

Conversions are less obvious, because they aren't associated with the = token (they can also happen at any other conversion site, such as passing a parameter.

[gafter]

@SLaks Deconstruction doesn't always happen at the =.

foreach (var (x, y) in e) // deconstruct on each element
var (x, (y, z)) = e; // nested deconstruction

[SLaks]

Good point.
For nested deconstructions, pressing F12 on = could show a FindSymbolResults window with every Deconstruct method being called (which may include duplicates). The TODO in my PR will do that.

For foreach, I'm not sure; maybe link to the in?
Or give up and not support foreach.

[jcouv]

Relates to #18963 (Find All References on Deconstruct method).