[Foundation] Import shims with @implementationOnly

stdlib/public/Darwin/Foundation/Calendar.swift

@@ -11,7 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 @_exported import Foundation // Clang module
-import _SwiftFoundationOverlayShims
+@_implementationOnly import _SwiftFoundationOverlayShims
 
 /**
  `Calendar` encapsulates information about systems of reckoning time in which the beginning, length, and divisions of a year are defined. It provides information about the calendar and support for calendrical computations such as determining the range of a given calendrical unit and adding units to a given absolute time.

stdlib/public/Darwin/Foundation/CharacterSet.swift

@@ -12,8 +12,8 @@
 
 @_exported import Foundation // Clang module
 import CoreFoundation
-import _SwiftCoreFoundationOverlayShims
-import _SwiftFoundationOverlayShims
+@_implementationOnly import _SwiftCoreFoundationOverlayShims
+@_implementationOnly import _SwiftFoundationOverlayShims
 
 private func _utfRangeToCFRange(_ inRange : Range<Unicode.Scalar>) -> CFRange {
     return CFRange(

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/FileManager.swift

@@ -11,7 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 @_exported import Foundation // Clang module
-import _SwiftFoundationOverlayShims
+@_implementationOnly import _SwiftFoundationOverlayShims
 
 extension FileManager {
     /*

stdlib/public/Darwin/Foundation/IndexPath.swift

@@ -11,7 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 @_exported import Foundation // Clang module
-import _SwiftFoundationOverlayShims
+@_implementationOnly import _SwiftFoundationOverlayShims
 
 /**
  `IndexPath` represents the path to a specific node in a tree of nested array collections.

stdlib/public/Darwin/Foundation/IndexSet.swift

@@ -11,7 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 @_exported import Foundation // Clang module
-import _SwiftFoundationOverlayShims
+@_implementationOnly import _SwiftFoundationOverlayShims
 
 extension IndexSet.Index {
     public static func ==(lhs: IndexSet.Index, rhs: IndexSet.Index) -> Bool {

stdlib/public/Darwin/Foundation/Locale.swift

@@ -11,7 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 @_exported import Foundation // Clang module
-import _SwiftFoundationOverlayShims
+@_implementationOnly import _SwiftFoundationOverlayShims
 
 /**
  `Locale` encapsulates information about linguistic, cultural, and technological conventions and standards. Examples of information encapsulated by a locale include the symbol used for the decimal separator in numbers and the way dates are formatted.

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/NSCoder.swift

@@ -11,7 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 @_exported import Foundation // Clang module
-import _SwiftFoundationOverlayShims
+@_implementationOnly import _SwiftFoundationOverlayShims
 
 //===----------------------------------------------------------------------===//
 // NSCoder

stdlib/public/Darwin/Foundation/NSDictionary.swift

@@ -11,7 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 @_exported import Foundation // Clang module
-import _SwiftFoundationOverlayShims
+@_implementationOnly import _SwiftFoundationOverlayShims
 
 // We don't check for NSCopying here for performance reasons. We would
 // just crash anyway, and NSMutableDictionary will still do that when

stdlib/public/Darwin/Foundation/NSError.swift

@@ -13,7 +13,7 @@
 @_exported import Foundation // Clang module
 import CoreFoundation
 import Darwin
-import _SwiftFoundationOverlayShims
+@_implementationOnly import _SwiftFoundationOverlayShims
 
 //===----------------------------------------------------------------------===//
 // NSError (as an out parameter).

stdlib/public/Darwin/Foundation/NSUndoManager.swift

@@ -11,7 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 @_exported import Foundation // Clang module
-import _SwiftFoundationOverlayShims
+@_implementationOnly import _SwiftFoundationOverlayShims
 
 extension UndoManager {
   @available(*, unavailable, renamed: "registerUndo(withTarget:handler:)")

stdlib/public/Darwin/Foundation/TimeZone.swift

@@ -11,7 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 @_exported import Foundation // Clang module
-import _SwiftFoundationOverlayShims
+@_implementationOnly import _SwiftFoundationOverlayShims
 
 /**
  `TimeZone` defines the behavior of a time zone. Time zone values represent geopolitical regions. Consequently, these values have names for these regions. Time zone values also represent a temporal offset, either plus or minus, from Greenwich Mean Time (GMT) and an abbreviation (such as PST for Pacific Standard Time).

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, *)

stdlib/public/SwiftShims/FoundationOverlayShims.h

@@ -34,44 +34,6 @@
 #import "NSTimeZoneShims.h"
 #import "NSUndoManagerShims.h"
 
-typedef struct {
-    void *_Nonnull memory;
-    size_t capacity;
-    _Bool onStack;
-} _ConditionalAllocationBuffer;
-
-static inline _Bool _resizeConditionalAllocationBuffer(_ConditionalAllocationBuffer *_Nonnull buffer, size_t amt) {
-    size_t amount = malloc_good_size(amt);
-    if (amount <= buffer->capacity) { return true; }
-    void *newMemory;
-    if (buffer->onStack) {
-        newMemory = malloc(amount);
-        if (newMemory == NULL) { return false; }
-        memcpy(newMemory, buffer->memory, buffer->capacity);
-        buffer->onStack = false;
-    } else {
-        newMemory = realloc(buffer->memory, amount);
-        if (newMemory == NULL) { return false; }
-    }
-    if (newMemory == NULL) { return false; }
-    buffer->memory = newMemory;
-    buffer->capacity = amount;
-    return true;
-}
-
-static inline _Bool _withStackOrHeapBuffer(size_t amount, void (__attribute__((noescape)) ^ _Nonnull applier)(_ConditionalAllocationBuffer *_Nonnull)) {
-    _ConditionalAllocationBuffer buffer;
-    buffer.capacity = malloc_good_size(amount);
-    buffer.onStack = (pthread_main_np() != 0 ? buffer.capacity < 2048 : buffer.capacity < 512);
-    buffer.memory = buffer.onStack ? alloca(buffer.capacity) : malloc(buffer.capacity);
-    if (buffer.memory == NULL) { return false; }
-    applier(&buffer);
-    if (!buffer.onStack) {
-        free(buffer.memory);
-    }
-    return true;
-}
-
 @protocol _NSKVOCompatibilityShim <NSObject>
 + (void)_noteProcessHasUsedKVOSwiftOverlay;
 @end