Destructuring and Narrowing

#47337

• If you narrow with "a" in value when value is generic, and then grab a with value.a, it works, but doesn't with destructuring.
  • Inconsistent!
• Sometimes it makes sense to get the base constraint in destructured valies instead of the generic, and sometimes it's best to keep the original type.
  • But threading the code to do that is difficult.
• Lots of bug reports where people say "oh no, I wanted the deferred version" or "I want the base constrained person"
• Seems like there are a well-understood set of cases that can be iterated on in the PR.