Add missing imports of _RegexParser

[tshortli]

While experimenting with adopting the MemberImportVisibility experimental feature (SE-0444) in the standard library build, I found that the _StringProcessing module was relying on transitive imports of _RegexParser in many source files.

[tshortli]

@swift-ci please test

[Azoy]

I'd prefer the attribute to appear on a newline above the import.

[tshortli]

Ok. How do you see this style mixing with multiple imports in the same file? To me this looked rather unusual and made it hard to scan the block of imports. I could also add a newline before internal import _RegexParser but that too looks unusual.

[Azoy]

My personal preference for attributes is always above the declaration it's attributing to. In the standard library for functions we have:

@available(SwiftStdlib 6.0, *)
func something() {
}

right, and for property wrappers my preference is also above the property declaration:

struct A {
  @propertyWrapper
  let b: Int

  let c: String
}

I think the newline before the 2nd property here makes sense to me and would similarly apply it to imports:

@attribute
import Swift

import A
import B

But again, this is just personal preference. I don't think we have a defined style yet for this because we just simply don't write imports with attributes often at all.

[tshortli]

I generally agree that attributes belong above declarations, especially when the list of attributes is likely to grow and line lengths can become an issue. For whatever reason, though, vibes-wise I don't think of imports as following the same rules as other declarations because it's so common for there to be an uninterrupted block of them at the top of a file. @_spi on a separate line really sticks out like a sore thumb to me, never seen it outside of this codebase. I'll follow your recommendation here, though, as I agree it seems to be the most consistent rule.

[tshortli]

@swift-ci please test