[stdlib] Optional: Initial support for noncopyable payloads

- Enable BorrowingSwitch feature within the stdlib - ExpressibleByNilLiteral: Add retroactive support for noncopyable conforming types - Optional: draft an API surface for noncopyable payloads
swiftlang · Feb 29, 2024 · e6dd049 · e6dd049
1 parent 1c2cb18
commit e6dd049
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Showing 4 changed files with 272 additions and 37 deletions.
diff --git a/stdlib/public/core/CMakeLists.txt b/stdlib/public/core/CMakeLists.txt
@@ -314,6 +314,7 @@ list(APPEND swift_stdlib_compile_flags "-enable-experimental-feature" "Macros")
 list(APPEND swift_stdlib_compile_flags "-enable-experimental-feature" "FreestandingMacros")
 list(APPEND swift_stdlib_compile_flags "-enable-experimental-feature" "Extern")
 list(APPEND swift_stdlib_compile_flags "-enable-experimental-feature" "BitwiseCopyable")
+list(APPEND swift_stdlib_compile_flags "-enable-experimental-feature" "BorrowingSwitch")
 
 if("${SWIFT_NATIVE_SWIFT_TOOLS_PATH}" STREQUAL "")
   set(swift_bin_dir "${CMAKE_BINARY_DIR}/bin")

diff --git a/stdlib/public/core/CompilerProtocols.swift b/stdlib/public/core/CompilerProtocols.swift
@@ -266,7 +266,7 @@ public protocol CaseIterable {
 /// `Optional` type conforms to `ExpressibleByNilLiteral`.
 /// `ExpressibleByNilLiteral` conformance for types that use `nil` for other
 /// purposes is discouraged.
-public protocol ExpressibleByNilLiteral {
+public protocol ExpressibleByNilLiteral: ~Copyable {
   /// Creates an instance initialized with `nil`.
   init(nilLiteral: ())
 }

diff --git a/stdlib/public/core/NFC.swift b/stdlib/public/core/NFC.swift
@@ -206,7 +206,7 @@ extension Unicode._InternalNFC.Iterator: IteratorProtocol {
     }
 
     // If we have a leftover composee, make sure to return it.
-    return composee._take()
+    return composee.take()
   }
 }