reduce name collisions

[aappddeevv]

Minimized example

trait Props extends js.Object { var basename: js.UndefOr[String] = js.undefined }

def basename(bname: js.UndefOr[String], children: ReactNode*) =
   createElement(JS, new Props { basename = bname }, children: _*)

Output

 [error] |Reference to basename is ambiguous

Expectation

Expectation is that this error should only occur if the name collision is because the name can be assigned to. Otherwise, it should assume that basename belongs to the data structure.

[prolativ]

Minimized without external dependencies:

trait Props { var basename: String = "" }
def basename(bname: String) = new Props { basename = bname }

@smarter do we want this to work without thisbasename = bname? You mentioned on gitter that dotty had got somehow stricter in such cases compared to scala2.

[smarter]

Yes, we're intentional stricter since #8622, but it's possible we could still get this example to work since only one of the two basename in scope are setters.

[odersky]

I'd rather not complicate the pec with fine-grained distinctions like that.