Add tests that exercise iteration API

Author: natecook1000

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/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

test/stdlib/Span/SpanTests.swift

@@ -607,3 +607,35 @@ suite.test("Span Sendability")
   let span = Span(_unsafeElements: buffer)
   send(span)
 }
+
+@available(SwiftStdlib 6.3, *)
+extension Sequence { // Copyable only
+  func collectViaBorrowing() -> [Element] {
+    var borrowIterator = makeBorrowingIterator()
+    var result: [Element] = []
+    while true {
+      let span = borrowIterator.nextSpan(maximumCount: .max)
+      if span.isEmpty { break }
+      for i in span.indices {
+        result.append(span[i])
+      }
+    }
+    return result
+  }
+}
+
+suite.test("BORROWING")
+.require(.stdlib_6_3).code {
+  guard #available(SwiftStdlib 6.3, *) else {
+    expectTrue(false)
+    return
+  }
+  
+  let array = [1, 2, 3, 4, 5, 6, 7, 8]
+  let arrayCollected = array.collectViaBorrowing()
+  expectEqual(array, arrayCollected)
+  
+  let inline: [8 of Int] = [1, 2, 3, 4, 5, 6, 7, 8]
+  let inlineCollected = inline.collectViaBorrowing()
+  expectEqualSequence(inline, inlineCollected)
+}