Feature flags 6.2-2025-06-14

Upcoming

📖 How to enable

BareSlashRegexLiterals

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ConciseMagicFile

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DeprecateApplicationMain

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DisableOutwardActorInference

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DynamicActorIsolation

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ExistentialAny

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ForwardTrailingClosures

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GlobalActorIsolatedTypesUsability

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GlobalConcurrency

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ImplicitOpenExistentials

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ImportObjcForwardDeclarations

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InferIsolatedConformances

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InferSendableFromCaptures

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InternalImportsByDefault

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IsolatedDefaultValues

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MemberImportVisibility

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NonfrozenEnumExhaustivity

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NonisolatedNonsendingByDefault

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RegionBasedIsolation

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StrictConcurrency

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• 💡 An Introduction to Isolation in Swift
• 💡 Data-race safety in Swift 5.10
• 💡 The Swift Book: Concurrency
• 💡 How to determine where tasks and async functions run in Swift?

Experimental

📖 How to enable

AccessLevelOnImport

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AdditiveArithmeticDerivedConformances

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AddressableParameters

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AddressableTypes

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AllowNonResilientAccessInPackage

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AllowRuntimeSymbolDeclarations

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AssumeResilientCxxTypes

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BuiltinMacros

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BuiltinModule

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CImplementation

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ClientBypassResilientAccessInPackage

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ClosureBodyMacro

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ClosureIsolation

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CodeItemMacros

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CompileTimeValues

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ConcurrencySyntaxSugar

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ConsumeSelfInDeinit

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CopyBlockOptimization

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CoroutineAccessors

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CoroutineAccessorsUnwindOnCallerError

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CustomAvailability

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DebugDescriptionMacro

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DefaultIsolationPerFile

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DifferentiableProgramming

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DoExpressions

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Embedded

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ExtensibleEnums

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Extern

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ExtractConstantsFromMembers

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FlowSensitiveConcurrencyCaptures

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ForwardModeDifferentiation

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FullTypedThrows

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GenerateBindingsForThrowingFunctionsInCXX

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GroupActorErrors

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ImplicitLastExprResults

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ImplicitSome

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ImportNonPublicCxxMembers

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ImportSymbolicCXXDecls

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InlineArrayTypeSugar

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InoutLifetimeDependence

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KeyPathWithMethodMembers

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LayoutPrespecialization

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LazyImmediate

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LifetimeDependence

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LifetimeDependenceMutableAccessors

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Lifetimes

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MacrosOnImports

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MoveOnlyClasses

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MoveOnlyEnumDeinits

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MoveOnlyPartialReinitialization

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MoveOnlyTuples

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NamedOpaqueTypes

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NoImplicitCopy

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ObjCImplementationWithResilientStorage

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OldOwnershipOperatorSpellings

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OpaqueTypeErasure

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PackageCMO

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ParserASTGen

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ParserRoundTrip

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ParserValidation

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PlaygroundExtendedCallbacks

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PreambleMacros

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RawLayout

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ReferenceBindings

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ReinitializeConsumeInMultiBlockDefer

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SafeInteropWrappers

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SameElementRequirements

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SE427NoInferenceOnExtension

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Sensitive

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StaticAssert

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StaticExclusiveOnly

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StructLetDestructuring

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SuppressCXXForeignReferenceTypeInitializers

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SuppressedAssociatedTypes

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SymbolLinkageMarkers

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ThenStatements

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TrailingComma

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TupleConformances

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UnqualifiedLookupValidation

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Volatile

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Stable

"embedded"

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"playground transform"

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ABIAttributeSE0479

@abi attribute on functions, initializers, properties, and subscripts

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Actors

actors

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AlwaysInheritActorContext

@_inheritActorContext(always)

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AssociatedTypeAvailability

Availability on associated types

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AssociatedTypeImplements

@_implements on associated types

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AsyncAwait

async/await

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AsyncExecutionBehaviorAttributes

@concurrent and nonisolated(nonsending)

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AsyncSequenceFailure

Failure associated type on AsyncSequence and AsyncIteratorProtocol

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AttachedMacros

Attached macros

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BitwiseCopyable

BitwiseCopyable protocol

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BitwiseCopyable2

BitwiseCopyable feature

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BodyMacros

Function body macros

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BorrowingSwitch

Noncopyable type pattern matching

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BuiltinAddressOfRawLayout

Builtin.addressOfRawLayout

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BuiltinAssumeAlignment

Builtin.assumeAlignment

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BuiltinBuildComplexEqualityExecutor

Executor-building for 'complexEquality executor' builtins

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BuiltinBuildExecutor

Executor-building builtins

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BuiltinBuildMainExecutor

MainActor executor building builtin

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BuiltinBuildTaskExecutorRef

TaskExecutor-building builtins

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BuiltinContinuation

Continuation builtins

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BuiltinCreateAsyncDiscardingTaskInGroup

Task create in discarding task group builtin, accounting for the Void return type

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BuiltinCreateAsyncDiscardingTaskInGroupWithExecutor

Task create in discarding task group with extra executor preference

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BuiltinCreateAsyncTaskInGroup

Task create in task group builtin with extra flags

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BuiltinCreateAsyncTaskInGroupWithExecutor

Task create in task group builtin with extra flags

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BuiltinCreateAsyncTaskName

Task create with a name

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BuiltinCreateAsyncTaskOwnedTaskExecutor

Task create with owned TaskExecutor

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BuiltinCreateAsyncTaskWithExecutor

Task create builtin with extra executor preference

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BuiltinCreateTask

Builtin.createTask and Builtin.createDiscardingTask

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BuiltinCreateTaskGroupWithFlags

Builtin.createTaskGroupWithFlags

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BuiltinEmplaceTypedThrows

Builtin.emplace typed throws

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BuiltinExecutor

Builtin.Executor type

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BuiltinHopToActor

Builtin.HopToActor

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BuiltinIntLiteralAccessors

Builtin.IntLiteral accessors

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BuiltinJob

Builtin.Job type

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BuiltinSelect

Builtin.select

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BuiltinStackAlloc

Builtin.stackAlloc

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BuiltinStoreRaw

Builtin.storeRaw

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BuiltinTaskGroupWithArgument

TaskGroup builtins

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BuiltinTaskRunInline

Builtin.taskRunInline

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BuiltinUnprotectedAddressOf

Builtin.unprotectedAddressOf

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BuiltinUnprotectedStackAlloc

Builtin.unprotectedStackAlloc

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ConcurrentFunctions

@concurrent functions

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ConformanceSuppression

Suppressible inferred conformances

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EffectfulProp

Effectful properties

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ExpressionMacroDefaultArguments

Expression macro as caller-side default argument

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ExtensionMacroAttr

@attached(extension)

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ExtensionMacros

Extension macros

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FreestandingExpressionMacros

Expression macros

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FreestandingMacros

freestanding declaration macros

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GeneralizedIsSameMetaTypeBuiltin

Builtin.is_same_metatype with support for noncopyable/nonescapable types

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GlobalActors

Global actors

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ImplicitSelfCapture

@_implicitSelfCapture attribute

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InheritActorContext

@_inheritActorContext attribute

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IsolatedAny

@isolated(any) function types

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IsolatedAny2

@isolated(any) function types

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IsolatedConformances

Global-actor isolated conformances

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IsolatedDeinit

isolated deinit

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LexicalLifetimes

@_eagerMove/@_noEagerMove/@_lexicalLifetimes annotations

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Macros

Macros

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MarkerProtocol

@_marker protocol

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MemorySafetyAttributes

@unsafe attribute

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MoveOnly

noncopyable types

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MoveOnlyPartialConsumption

Partial consumption of noncopyable values

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MoveOnlyResilientTypes

non-@frozen noncopyable types with library evolution

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NewCxxMethodSafetyHeuristics

Only import C++ methods that return pointers (projections) on owned types as unsafe

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NoAsyncAvailability

@available(*, noasync)

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NoncopyableGenerics

Noncopyable generics

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NoncopyableGenerics2

Noncopyable generics alias

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NonescapableTypes

Nonescapable types

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ObjCImplementation

@objc @implementation extensions

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OptionalIsolatedParameters

Optional isolated parameters

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ParameterPacks

Value and type parameter packs

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PrimaryAssociatedTypes2

Primary associated types

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RawIdentifiers

Raw identifiers

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RethrowsProtocol

@rethrows protocol

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RetroactiveAttribute

@retroactive

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Sendable

Sendable and @Sendable

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SendableCompletionHandlers

Objective-C completion handler parameters are imported as @Sendable

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SendingArgsAndResults

Sending arg and results

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SpecializeAttributeWithAvailability

@_specialize attribute with availability

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StrictMemorySafety

Strict memory safety

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TypedThrows

Typed throws

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UnavailableFromAsync

@_unavailableFromAsync

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UnsafeInheritExecutor

@_unsafeInheritExecutor

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ValueGenerics

Value generics feature (integer generics)

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ValueGenericsNameLookup

Value generics appearing as static members for namelookup

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