[WIP] Iterate on BorrowIteration

Runtimes/Core/Core/CMakeLists.txt

@@ -42,6 +42,7 @@ add_library(swiftCore
   BidirectionalCollection.swift
   Bitset.swift
   Bool.swift
+  BorrowIteratorProtocol.swift
   BridgeObjectiveC.swift
   BridgeStorage.swift
   BridgingBuffer.swift
@@ -93,6 +94,7 @@ add_library(swiftCore
   InputStream.swift
   IntegerParsing.swift
   Integers.swift
+  Iterable.swift
   Join.swift
   KeyPath.swift
   KeyValuePairs.swift

Runtimes/Core/cmake/modules/ExperimentalFeatures.cmake

@@ -13,4 +13,5 @@ add_compile_options(
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-enable-experimental-feature BitwiseCopyable>"
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-enable-experimental-feature Extern>"
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-enable-experimental-feature AllowUnsafeAttribute>"
-  "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-enable-experimental-feature ValueGenerics>")
+  "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-enable-experimental-feature ValueGenerics>"
+  "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-enable-experimental-feature Lifetimes>")

benchmark/single-source/DataBenchmarks.swift

@@ -327,14 +327,20 @@ let large = sampleData(.large)
 let array809 = byteArray(size: 809)
 
 struct Count0<S: Sequence> : Sequence {
+  @available(macOS 9999, *)
+  public typealias BorrowingIterator = BorrowingIteratorAdapter<S.Iterator>
+
   let base: S
   init (_ base:S) { self.base = base }
   func makeIterator() -> S.Iterator { return base.makeIterator() }
   var underestimatedCount: Int { return 0 }
 }
 
 struct Bytes: Sequence, IteratorProtocol {
-    let count: Int
+  @available(macOS 9999, *)
+  public typealias BorrowingIterator = BorrowingIteratorAdapter<Self>
+
+  let count: Int
     let exact: Bool
     var  i: Int = 0
     init(count: Int, exact: Bool) {

stdlib/cmake/modules/SwiftSource.cmake

@@ -342,15 +342,15 @@ function(_add_target_variant_swift_compile_flags
   if(SWIFT_STDLIB_OS_VERSIONING)
     list(APPEND result "-D" "SWIFT_RUNTIME_OS_VERSIONING")
   endif()
-  
+
   if(SWIFT_STDLIB_STATIC_PRINT)
     list(APPEND result "-D" "SWIFT_STDLIB_STATIC_PRINT")
   endif()
-  
+
   if(SWIFT_STDLIB_ENABLE_UNICODE_DATA)
     list(APPEND result "-D" "SWIFT_STDLIB_ENABLE_UNICODE_DATA")
   endif()
-  
+
   if(SWIFT_STDLIB_ENABLE_VECTOR_TYPES)
     list(APPEND result "-D" "SWIFT_STDLIB_ENABLE_VECTOR_TYPES")
   endif()
@@ -612,7 +612,7 @@ function(_compile_swift_files
     list(APPEND swift_flags "-autolink-force-load")
   endif()
 
-  # Don't need to link runtime compatibility libraries for older runtimes 
+  # Don't need to link runtime compatibility libraries for older runtimes
   # into the new runtime.
   if (SWIFTFILE_IS_STDLIB OR SWIFTFILE_IS_SDK_OVERLAY)
     list(APPEND swift_flags "-runtime-compatibility-version" "none")
@@ -640,6 +640,7 @@ function(_compile_swift_files
   list(APPEND swift_flags "-enable-experimental-feature" "LifetimeDependence")
   list(APPEND swift_flags "-enable-experimental-feature" "InoutLifetimeDependence")
   list(APPEND swift_flags "-enable-experimental-feature" "LifetimeDependenceMutableAccessors")
+  list(APPEND swift_flags "-enable-experimental-feature" "Lifetimes")
 
   list(APPEND swift_flags "-enable-upcoming-feature" "MemberImportVisibility")
 

stdlib/private/StdlibCollectionUnittest/MinimalCollections.swift

@@ -83,6 +83,8 @@ public enum UnderestimatedCountBehavior {
 ///
 /// This sequence is consumed when its generator is advanced.
 public struct MinimalSequence<T> : Sequence, CustomDebugStringConvertible {
+  public typealias Element = T
+
   public init<S : Sequence>(
     elements: S,
     underestimatedCount: UnderestimatedCountBehavior = .value(0)

stdlib/private/StdlibUnittest/StdlibUnittest.swift

@@ -2241,7 +2241,8 @@ public enum StdLibVersion: String {
   case stdlib_6_0  = "6.0"
   case stdlib_6_1  = "6.1"
   case stdlib_6_2  = "6.2"
-
+  case stdlib_6_3  = "6.3"
+
   var isAvailable: Bool {
     switch self {
     case .stdlib_5_7:
@@ -2258,6 +2259,8 @@ public enum StdLibVersion: String {
       return if #available(SwiftStdlib 6.1, *)  { true } else { false }
     case .stdlib_6_2:
       return if #available(SwiftStdlib 6.2, *)  { true } else { false }
+    case .stdlib_6_3:
+      return if #available(SwiftStdlib 6.3, *)  { true } else { false }
     }
   }
 }

stdlib/private/SwiftReflectionTest/SwiftReflectionTest.swift

@@ -226,6 +226,10 @@ internal struct Section {
 
 /// Holds the addresses and sizes of sections related to reflection.
 internal struct ReflectionInfo : Sequence {
+  internal typealias Element = Section?
+  @available(macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, *)
+  internal typealias BorrowingIterator = BorrowingIteratorAdapter<AnyIterator<Section?>>
+
   /// The name of the loaded image.
   internal let imageName: String
 

stdlib/public/Concurrency/Deque/Deque+Collection.swift

@@ -19,6 +19,8 @@ extension _Deque: Sequence {
   // This custom implementation performs direct storage access to eliminate any
   // and all index validation overhead. It also optimizes away repeated
   // conversions from indices to storage slots.
+  @available(macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, *)
+  internal typealias BorrowingIterator = BorrowingIteratorAdapter<Iterator>
 
   /// An iterator over the members of a deque.
   struct Iterator: IteratorProtocol {

stdlib/public/RuntimeModule/Base64.swift

@@ -217,6 +217,8 @@ public struct Base64Encoder<S: Sequence>: Sequence
 public struct Base64Decoder<S: Sequence>: Sequence
   where S.Element == UTF8.CodeUnit
 {
+  @available(macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, *)
+  public typealias BorrowingIterator = BorrowingIteratorAdapter<Iterator>
   public typealias Element = UInt8
 
   var source: S

stdlib/public/RuntimeModule/Elf.swift

@@ -1266,6 +1266,8 @@ final class ElfImage<SomeElfTraits: ElfTraits>
   }
 
   struct Notes: Sequence {
+    typealias Element = Note
+
     var image: ElfImage<Traits>
 
     struct NoteIterator: IteratorProtocol {

stdlib/public/RuntimeModule/FramePointerUnwinder.swift

@@ -21,6 +21,7 @@ public struct FramePointerUnwinder<C: Context, M: MemoryReader>: Sequence, Itera
   public typealias Context = C
   public typealias MemoryReader = M
   public typealias Address = Context.Address
+  public typealias Element = RichFrame<Address>
 
   var pc: Address
   var fp: Address

stdlib/public/StringProcessing/CMakeLists.txt

@@ -20,6 +20,7 @@ set(swift_string_processing_compile_flags)
 # will be built with library evolution.
 list(APPEND swift_string_processing_compile_flags
   "-DRESILIENT_LIBRARIES")
+list(APPEND swift_string_processing_compile_flags "-Xfrontend" "-disable-availability-checking")
 
 if(SWIFT_BUILD_STATIC_STDLIB)
   # Explicitly autolink swift_RegexParser because it's imported with @_implementationOnly

stdlib/public/core/Array.swift

@@ -498,7 +498,7 @@ extension Array: _ArrayProtocol {
     @inlinable // FIXME(inline-always)
     @inline(__always)
     get {
-      return _buffer.owner      
+      return _buffer.owner
     }
   }
 
@@ -511,6 +511,18 @@ extension Array: _ArrayProtocol {
   }
 }
 
+extension Array: Sequence {
+  @available(SwiftStdlib 6.3, *)
+  public typealias BorrowingIterator = Span<Element>
+
+  @available(SwiftStdlib 6.3, *)
+  @lifetime(borrow self)
+  @_transparent
+  public func makeBorrowingIterator() -> BorrowingIterator {
+    span
+  }
+}
+
 extension Array: RandomAccessCollection, MutableCollection {
   /// The index type for arrays, `Int`.
   public typealias Index = Int
@@ -814,7 +826,7 @@ extension Array: RandomAccessCollection, MutableCollection {
       }
     }
   }
-  
+
   /// The number of elements in the array.
   @inlinable
   @_semantics("array.get_count")
@@ -1249,14 +1261,14 @@ extension Array: RangeReplaceableCollection {
     let oldCount = _buffer.mutableCount
     let startNewElements = unsafe _buffer.mutableFirstElementAddress + oldCount
     let buf = unsafe UnsafeMutableBufferPointer(
-                start: startNewElements, 
+                start: startNewElements,
                 count: _buffer.mutableCapacity - oldCount)
 
     var (remainder,writtenUpTo) = unsafe buf.initialize(from: newElements)
-    
+
     // trap on underflow from the sequence's underestimate:
     let writtenCount = unsafe buf.distance(from: buf.startIndex, to: writtenUpTo)
-    _precondition(newElementsCount <= writtenCount, 
+    _precondition(newElementsCount <= writtenCount,
       "newElements.underestimatedCount was an overestimate")
     // can't check for overflow as sequences can underestimate
 
@@ -1440,7 +1452,7 @@ extension Array: RangeReplaceableCollection {
       return try unsafe body(bufferPointer)
     }
   }
-  
+
   @inlinable
   public __consuming func _copyToContiguousArray() -> ContiguousArray<Element> {
     if let n = _buffer.requestNativeBuffer() {
@@ -1799,7 +1811,7 @@ extension Array {
     // a precondition and Array never lies about its count.
     guard var p = buffer.baseAddress
       else { _preconditionFailure("Attempt to copy contents into nil buffer pointer") }
-    _precondition(self.count <= buffer.count, 
+    _precondition(self.count <= buffer.count,
       "Insufficient space allocated to copy array contents")
 
     if let s = unsafe _baseAddressIfContiguous {
@@ -2160,3 +2172,25 @@ internal struct _ArrayAnyHashableBox<Element: Hashable>
 }
 
 extension Array: @unchecked Sendable where Element: Sendable { }
+
+// FIXME: This should be accepted, but we get the following:
+// error: type 'Array<Element>' does not conform to protocol 'Iterable'
+// note: multiple matching functions named '_customContainsEquatableElement' with type '(borrowing Array<Element>.Element) -> Bool?' (aka '(borrowing Element) -> Optional<Bool>')
+
+// @available(SwiftStdlib 6.3, *)
+// extension Array: Iterable {
+//   public typealias BorrowIterator = Span<Element>.BorrowIterator
+
+//   @_alwaysEmitIntoClient
+//   @_transparent
+//   public var estimatedCount: EstimatedCount {
+//     .exactly(count)
+//   }
+
+//   @_alwaysEmitIntoClient
+//   @_lifetime(borrow self)
+//   @_transparent
+//   public func startBorrowIteration() -> Span<Element> {
+//     self.span
+//   }
+// }