unused_optional_binding misses ifs inside functions

[keith]

This example does not trigger the unused_optional_binding:

func foo() {
    if let _ = bar {
    }
}

If you add this test case:

"func foo() {\nif let _ = bar {\n}\n"

You can see that the tests fail to pass. I believe this is because the if in this case is nested in the substructure of the func, which isn't handled by the current logic

// @rakaramos

[marcelofabri]

I think this is a problem on the default implementation of ASTRule: https://github.com/realm/SwiftLint/blob/master/Source/SwiftLintFramework/Protocols/ASTRule.swift#L21. It only looks at substructures of the same KindType.

[keith]

Ah yep! Looks believable. Do you know of any immediate problems we'd have if we "fixed" that?

[marcelofabri]

I can only think about performance regressions, but we should care more about correctness in this case 😅