Working build!

Author: natecook1000

stdlib/public/core/BorrowingIteratorProtocol.swift

@@ -148,6 +148,26 @@ extension Span: BorrowingIteratorProtocol where Element: ~Copyable {
   }
 }
 
+@available(SwiftStdlib 6.3, *)
+extension Span /*: Sequence /* where Element: ~Copyable */ */ {
+  @_alwaysEmitIntoClient
+  @_lifetime(borrow self)
+  public func makeBorrowingIterator() -> Span<Element> {
+    self
+  }
+}
+
+extension InlineArray: Sequence /* where Element: ~Copyable */ {
+  public typealias Element = Element
+  public typealias Iterator = NeverIterator<Element>
+  
+  @_alwaysEmitIntoClient
+  @_lifetime(borrow self)
+  public func makeBorrowingIterator() -> Span<Element> {
+    self.span
+  }
+}
+
 //@available(SwiftStdlib 6.3, *)
 //extension MutableSpan: Iterable where Element: ~Copyable {
 //  public typealias BorrowIterator = Span<Element>.BorrowIterator

stdlib/public/core/CMakeLists.txt

@@ -340,6 +340,7 @@ endif()
 
 # STAGING: Temporarily avoids having to write #fileID in Swift.swiftinterface.
 list(APPEND swift_stdlib_compile_flags "-Xfrontend" "-enable-experimental-concise-pound-file")
+list(APPEND swift_stdlib_compile_flags "-Xfrontend" "-disable-availability-checking")
 
 list(APPEND swift_stdlib_compile_flags "-enable-experimental-feature" "Macros")
 list(APPEND swift_stdlib_compile_flags "-enable-experimental-feature" "FreestandingMacros")

stdlib/public/core/Sequence.swift

@@ -331,8 +331,7 @@ public protocol Sequence<Element> /* : ~Copyable, ~Escapable */ {
   associatedtype Iterator: IteratorProtocol<Element>
 
   @available(SwiftStdlib 6.3, *)
-  associatedtype BorrowingIterator: BorrowingIteratorProtocol & ~Copyable & ~Escapable /* where BorrowingIterator.Element == Element */
-    = BorrowingIteratorAdapter<Self>
+  associatedtype BorrowingIterator: BorrowingIteratorProtocol<Element> & ~Copyable & ~Escapable = BorrowingIteratorAdapter<Self>
 
   // FIXME: <rdar://problem/34142121>
   // This typealias should be removed as it predates the source compatibility
@@ -465,7 +464,9 @@ public struct BorrowingIteratorAdapter<S: Sequence>: /* & ~Copyable & ~Escapable
 {
   var iterator: S.Iterator
   var curValue: S.Element?
-  
+ 
+  public typealias Element = S.Element
+
   @lifetime(&self)
   public mutating func nextSpan(maximumCount: Int) -> Span<S.Element> {
     curValue = iterator.next()
@@ -480,7 +481,7 @@ public enum NeverIterator<Element: ~Copyable> {}
 extension NeverIterator: IteratorProtocol { /* where Element: ~Copyable */
   public typealias Element = Element
   public func next() -> Element? {
-    fatalError()
+    Builtin.unreachable()
   }
 }
 
@@ -491,6 +492,13 @@ extension Sequence where BorrowingIterator == BorrowingIteratorAdapter<Self> {
   }
 }
 
+@available(SwiftStdlib 6.3, *)
+extension Sequence where Iterator == NeverIterator<Element> {
+  public func makeIterator() -> Iterator {
+    fatalError("Attempt to iterate using a NeverIterator")
+  }
+}
+
 // Provides a default associated type witness for Iterator when the
 // Self type is both a Sequence and an Iterator.
 extension Sequence where Self: IteratorProtocol {