[Foundation] Switch to private imports of CoreFoundation shims

Author: lorentey

stdlib/public/Darwin/Foundation/CharacterSet.swift

@@ -12,7 +12,7 @@
 
 @_exported import Foundation // Clang module
 import CoreFoundation
-import _SwiftCoreFoundationOverlayShims
+@_implementationOnly import _SwiftCoreFoundationOverlayShims
 @_implementationOnly import _SwiftFoundationOverlayShims
 
 private func _utfRangeToCFRange(_ inRange : Range<Unicode.Scalar>) -> CFRange {

stdlib/public/Darwin/Foundation/Data.swift

@@ -42,7 +42,7 @@ internal func __NSDataIsCompact(_ data: NSData) -> Bool {
 
 @_exported import Foundation // Clang module
 @_implementationOnly import _SwiftFoundationOverlayShims
-import _SwiftCoreFoundationOverlayShims
+@_implementationOnly import _SwiftCoreFoundationOverlayShims
 
 internal func __NSDataIsCompact(_ data: NSData) -> Bool {
     if #available(OSX 10.10, iOS 8.0, tvOS 9.0, watchOS 2.0, *) {

stdlib/public/Darwin/Foundation/Date.swift

@@ -12,7 +12,7 @@
 
 @_exported import Foundation // Clang module
 import CoreFoundation
-import _SwiftCoreFoundationOverlayShims
+@_implementationOnly import _SwiftCoreFoundationOverlayShims
 
 /**
  `Date` represents a single point in time.

stdlib/public/Darwin/Foundation/DateInterval.swift

@@ -11,7 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 @_exported import Foundation // Clang module
-import _SwiftCoreFoundationOverlayShims
+@_implementationOnly import _SwiftCoreFoundationOverlayShims
 
 /// DateInterval represents a closed date interval in the form of [startDate, endDate].  It is possible for the start and end dates to be the same with a duration of 0.  DateInterval does not support reverse intervals i.e. intervals where the duration is less than 0 and the end date occurs earlier in time than the start date.
 @available(macOS 10.12, iOS 10.0, watchOS 3.0, tvOS 10.0, *)

stdlib/public/Darwin/Foundation/Decimal.swift

@@ -11,7 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 @_exported import Foundation // Clang module
-import _SwiftCoreFoundationOverlayShims
+@_implementationOnly import _SwiftCoreFoundationOverlayShims
 
 extension Decimal {
     public typealias RoundingMode = NSDecimalNumber.RoundingMode

stdlib/public/Darwin/Foundation/Measurement.swift

@@ -14,7 +14,7 @@
 import CoreFoundation
 #else
 @_exported import Foundation // Clang module
-import _SwiftCoreFoundationOverlayShims
+@_implementationOnly import _SwiftCoreFoundationOverlayShims
 #endif
 
 /// A `Measurement` is a model type that holds a `Double` value associated with a `Unit`.

stdlib/public/Darwin/Foundation/UUID.swift

@@ -12,7 +12,7 @@
 
 @_exported import Foundation // Clang module
 import Darwin.uuid
-import _SwiftCoreFoundationOverlayShims
+@_implementationOnly import _SwiftCoreFoundationOverlayShims
 
 /// Represents UUID strings, which can be used to uniquely identify types, interfaces, and other items.
 @available(macOS 10.8, iOS 6.0, *)