Incorrectly parsed directives

[ketkarameya]

I observed that the directives (https://docs.swift.org/swift-book/documentation/the-swift-programming-language/statements/#Compiler-Control-Statements) do not parse well.

class Sample {


    public static func foobar() -> Bool {
        #if DEBUG
            return true
        #else
            return false
        #endif
    }

}

Tree:

body: [function_body][3, 40] - [9, 5]
          [directive][4, 8] - [4, 17]
          [statements][5, 12] - [8, 8]
            [control_transfer_statement][5, 12] - [5, 23]
              result: [boolean_literal][5, 19] - [5, 23]
            [directive][6, 8] - [6, 13]
            [control_transfer_statement][7, 12] - [7, 24]
              result: [boolean_literal][7, 19] - [7, 24]
          [directive][8, 8] - [8, 14]

I think the [statements][5, 12] ... [directive][8, 8] - [8, 14] should be nested under [directive][4, 8] - [4, 17] ?
And in some sense the we need the entire if-elseif like parsing here.

[alex-pinkus]

Yep, we parse directives like extras, but Swift is actually restrictive enough with its macro system that we can do better. That is, I was leaving open the possibility that there could be something like:

class MyClass
#if DEBUG
}
#else
}
class MyOtherClass
#endif
}

But Swift doesn't allow this case (it says "Unexpected '}' in conditional compilation block"), and I suspect they disallow any such cases. It probably makes sense to just add this into the choice in _local_statement and _top_level_statement, and add the structure for the if/else like you say.