This allows building sourcekitd and swift-refactor with `SWIFT_BUILD_SWIFT_SYNTAX=NO`. In these builds, the `relatedidents` and `find-syntactic-rename-ranges` requests will always return an error.
For enum cases with associated values, their construction is modelled by a function. E.g. if you have
```swift
enum Foo {
case first(associated: Int)
}
```
then `Foo.first` is a function of type `(Int) -> Foo`. But if you write `Foo.first(associated: 2)` in source code, we consider this construct as a referenced, not a call. This causes us to miss renaming of associated value labels during local refactoring.
rdar://84061868