Optimize keypaths in language 6 mode

[eeckstein]

In language 6 mode keypath instructions are created as existentials and the optimizer needs to look through the open_existential_ref instructions to recognize a keypath.

rdar://150173106

[eeckstein]

@swift-ci test

[slavapestov]

What changes in Swift 6 mode?

[eeckstein]

What changes in Swift 6 mode?

keypath literals are created as existentials:

  %2 = keypath $any WritableKeyPath<Element, Int> & Sendable, (root $Element; stored_property #Element.id : $Int) // user: %3
  %3 = open_existential_ref %2 to $@opened("C446880C-244A-11F0-AE41-0EA13E3AABB1", any WritableKeyPath<Element, Int> & Sendable) Self // user: %4

[dnadoba]

Swift 6 mode enables -enable-upcoming-feature InferSendableFromCaptures which causes & Sendable to be inferred.

[slavapestov]

Ah I see.

[aschwaighofer]

lgtm

[xedin]

Yes, key path type-checking is different due to InferSendableFromCaptures, maybe we should be doing something else on the Sema side instead?

[eeckstein]

maybe we should be doing something else on the Sema side instead?

Anyway, with this change, the optimizer can handle the existential keypath