self.self.self.self.self compilation issue

[endeavour42]

Description
self.self.self.self.self compilation issue

Steps to reproduce
This compiles:

struct Foo {
    subscript(index: Int) -> Int { 42 }
    
    func foo() {
        _ = self.self.self.self.self[1] // any number of self
    }
}

Expected behavior

It should give a compilation error.

Environment

• Swift compiler version info 5.7
• Xcode version info 14.0.1

[AnthonyLatsis]

Why shouldn’t it compile? x.self (including self.self) is a valid expression, and an identity transform.