Merge pull request #80163 from swiftlang/gaborh/vector-span-property

[cxx-interop] Add span property to std::vector

Author: Xazax-hun

lib/ClangImporter/ClangDerivedConformances.cpp

@@ -1079,7 +1079,9 @@ void swift::conformToCxxVectorIfNeeded(ClangImporter::Implementation &impl,
       decl, ctx.getIdentifier("value_type"));
   auto iterType = lookupDirectSingleWithoutExtensions<TypeAliasDecl>(
       decl, ctx.getIdentifier("const_iterator"));
-  if (!valueType || !iterType)
+  auto sizeType = lookupDirectSingleWithoutExtensions<TypeAliasDecl>(
+      decl, ctx.getIdentifier("size_type"));
+  if (!valueType || !iterType || !sizeType)
     return;
 
   ProtocolDecl *cxxRandomAccessIteratorProto =
@@ -1097,6 +1099,8 @@ void swift::conformToCxxVectorIfNeeded(ClangImporter::Implementation &impl,
                                valueType->getUnderlyingType());
   impl.addSynthesizedTypealias(decl, ctx.Id_ArrayLiteralElement,
                                valueType->getUnderlyingType());
+  impl.addSynthesizedTypealias(decl, ctx.getIdentifier("Size"),
+                               sizeType->getUnderlyingType());
   impl.addSynthesizedTypealias(decl, ctx.getIdentifier("RawIterator"),
                                rawIteratorTy);
   impl.addSynthesizedProtocolAttrs(decl, {KnownProtocolKind::CxxVector});

stdlib/public/Cxx/CxxVector.swift

@@ -17,10 +17,14 @@ public protocol CxxVector<Element>: ExpressibleByArrayLiteral {
   associatedtype Element
   associatedtype RawIterator: UnsafeCxxRandomAccessIterator
     where RawIterator.Pointee == Element
+  associatedtype Size: BinaryInteger
 
   init()
 
   mutating func push_back(_ element: Element)
+
+  func size() -> Size
+  func __dataUnsafe() -> UnsafePointer<Element>?
 }
 
 extension CxxVector {
@@ -45,3 +49,16 @@ extension CxxVector {
     self.init(elements)
   }
 }
+
+@available(SwiftStdlib 6.2, *)
+extension CxxVector {
+  public var span: Span<Element> {
+    @lifetime(borrow self)
+    @_alwaysEmitIntoClient
+    borrowing get {
+      let buffer = unsafe UnsafeBufferPointer(start: self.__dataUnsafe(), count: Int(self.size()))
+      let span = unsafe Span(_unsafeElements: buffer)
+      return unsafe _cxxOverrideLifetime(span, borrowing: self)
+    }
+  }
+}

test/Interop/Cxx/stdlib/use-std-vector.swift

@@ -190,4 +190,19 @@ StdVectorTestSuite.test("VectorOfString subclass for loop") {
     expectEqual(count, 1)
 }
 
+StdVectorTestSuite.test("VectorOfInt to span").require(.stdlib_6_2).code {
+  guard #available(SwiftStdlib 6.2, *) else { return }
+
+  let v = Vector([1, 2, 3])
+  // FIXME: remove 'withExtendedLifetime' once lifetime analysis is fixed.
+  withExtendedLifetime(v) {
+    let s = $0.span
+    expectEqual(s.count, 3)
+    expectFalse(s.isEmpty)
+    expectEqual(s[0], 1)
+    expectEqual(s[1], 2)
+    expectEqual(s[2], 3)
+  }
+}
+
 runAllTests()