Adopt @abi in the standard library

This commit enables the ABIAttribute feature in the standard library build and replaces (nearly) every instance of `@_silgen_name(<mangled Swift name>)` in stdlib/public with an `@abi` attribute.

Author: beccadax

Diff for: docs/ReferenceGuides/UnderscoredAttributes.md

@@ -1131,15 +1131,17 @@ ways to misuse it:
   be reliably recovered through C interfaces like `dlsym`. If you want to
   implement a plugin-style interface, use `Bundle`/`NSBundle` if available, or
   export your plugin entry points as C entry points using `@_cdecl`.
-  
+- Don't use `@_silgen_name` when you need to make a change to an ABI-stable
+  declaration's signature that would normally alter its mangled name, but you
+  need to preserve the old mangled name for ABI compatibility. We used to use it
+  for this task, but `@abi` can do it with fewer limitations, more safety, and
+  better readability. If for some reason you do need `@_silgen_name`, you will
+  need to be careful that the change doesn't materially affect the actual
+  calling convention of the function in an incompatible way.
+
 Legitimate uses may include:
 
 - Use `@_silgen_name` if you're implementing the Swift runtime.
-- Use `@_silgen_name` if you need to make a change to an ABI-stable
-  declaration's signature that would normally alter its mangled name, but you
-  need to preserve the old mangled name for ABI compatibility. You will need
-  to be careful that the change doesn't materially affect the actual calling
-  convention of the function in an incompatible way.
 - Use `@_silgen_name` if certain declarations need to have predictable symbol
   names, such as to be easily referenced by linker scripts or other highly
   customized build environments (and it's OK for those predictable symbols to

Diff for: docs/StandardLibraryProgrammersManual.md

@@ -455,6 +455,8 @@ This attribute specifies the name that a declaration will have at link time. It
 1. To specify the symbol name of a Swift function so that it can be called from Swift-aware C. Such functions have bodies.
 2. To provide a Swift declaration which really represents a C declaration. Such functions do not have bodies.
 
+In the past it was sometimes used for ABI backwards compatibility hacks, but `@abi` does this job better.
+
 ##### Using `@_silgen_name` to call Swift from Swift-aware C
 
 Rather than hard-code Swift mangling into C code, `@_silgen_name` is used to provide a stable and known symbol name for linking. Note that C code still must understand and use the Swift calling convention (available in swift-clang) for such Swift functions (if they use Swift's CC). Example:

Diff for: stdlib/cmake/modules/SwiftSource.cmake

@@ -631,6 +631,7 @@ function(_compile_swift_files
 
   list(APPEND swift_flags "-enable-experimental-feature" "NonescapableTypes")
   list(APPEND swift_flags "-enable-experimental-feature" "LifetimeDependence")
+  list(APPEND swift_flags "-enable-experimental-feature" "ABIAttribute")
 
   list(APPEND swift_flags "-enable-upcoming-feature" "MemberImportVisibility")
 

Diff for: stdlib/public/Concurrency/AsyncStream.swift

@@ -330,7 +330,12 @@ public struct AsyncStream<Element> {
   ///     }
   ///
   ///
-  @_silgen_name("$sScS9unfolding8onCancelScSyxGxSgyYac_yyYbcSgtcfC")
+  @abi(
+    init(
+      unfolding produce: @escaping /* not @Sendable*/ () async -> Element?,
+      onCancel: (@Sendable () -> Void)?
+    )
+  )
   @preconcurrency // Original API had `@Sendable` only on `onCancel`
   public init(
     unfolding produce: @escaping @Sendable () async -> Element?,

Diff for: stdlib/public/Concurrency/CheckedContinuation.swift

@@ -313,9 +313,14 @@ public func withCheckedContinuation<T>(
 //
 // This function also doubles as an ABI-compatibility shim predating the
 // introduction of #isolation.
+@abi(
+  func withCheckedContinuation<T>(
+    function: String,
+    _ body: (CheckedContinuation<T, Never>) -> Void
+  ) async -> T
+)
 @available(SwiftStdlib 5.1, *)
 @_unsafeInheritExecutor // ABI compatibility with Swift 5.1
-@_silgen_name("$ss23withCheckedContinuation8function_xSS_yScCyxs5NeverOGXEtYalF")
 public func _unsafeInheritExecutor_withCheckedContinuation<T>(
   function: String = #function,
   _ body: (CheckedContinuation<T, Never>) -> Void
@@ -377,9 +382,14 @@ public func withCheckedThrowingContinuation<T>(
 //
 // This function also doubles as an ABI-compatibility shim predating the
 // introduction of #isolation.
+@abi(
+  func withCheckedThrowingContinuation<T>(
+    function: String,
+    _ body: (CheckedContinuation<T, Error>) -> Void
+  ) async throws -> T
+)
 @available(SwiftStdlib 5.1, *)
 @_unsafeInheritExecutor // ABI compatibility with Swift 5.1
-@_silgen_name("$ss31withCheckedThrowingContinuation8function_xSS_yScCyxs5Error_pGXEtYaKlF")
 public func _unsafeInheritExecutor_withCheckedThrowingContinuation<T>(
   function: String = #function,
   _ body: (CheckedContinuation<T, Error>) -> Void

Diff for: stdlib/public/Concurrency/DiscardingTaskGroup.swift

@@ -97,9 +97,14 @@ public func withDiscardingTaskGroup<GroupResult>(
 //
 // This function also doubles as an ABI-compatibility shim predating the
 // introduction of #isolation.
+@abi(
+  func withDiscardingTaskGroup<GroupResult>(
+    returning returnType: GroupResult.Type,
+    body: (inout DiscardingTaskGroup) async -> GroupResult
+  ) async -> GroupResult
+)
 @available(SwiftStdlib 5.9, *)
 @_unsafeInheritExecutor // for ABI compatibility
-@_silgen_name("$ss23withDiscardingTaskGroup9returning4bodyxxm_xs0bcD0VzYaXEtYalF")
 public func _unsafeInheritExecutor_withDiscardingTaskGroup<GroupResult>(
   returning returnType: GroupResult.Type = GroupResult.self,
   body: (inout DiscardingTaskGroup) async -> GroupResult
@@ -367,9 +372,14 @@ public func withThrowingDiscardingTaskGroup<GroupResult>(
   return result
 }
 
+@abi(
+  func withThrowingDiscardingTaskGroup<GroupResult>(
+      returning returnType: GroupResult.Type,
+      body: (inout ThrowingDiscardingTaskGroup<Error>) async throws -> GroupResult
+  ) async throws -> GroupResult
+)
 @available(SwiftStdlib 5.9, *)
 @_unsafeInheritExecutor // for ABI compatibility
-@_silgen_name("$ss31withThrowingDiscardingTaskGroup9returning4bodyxxm_xs0bcdE0Vys5Error_pGzYaKXEtYaKlF")
 public func _unsafeInheritExecutor_withThrowingDiscardingTaskGroup<GroupResult>(
     returning returnType: GroupResult.Type = GroupResult.self,
     body: (inout ThrowingDiscardingTaskGroup<Error>) async throws -> GroupResult

Diff for: stdlib/public/Concurrency/ExecutorAssertions.swift

@@ -368,11 +368,16 @@ extension Actor {
     }
   }
 
+  @abi(
+    nonisolated func assumeIsolated<T /* not ': Sendable' */>(
+        _ operation: (isolated Self) throws -> T,
+        file: StaticString, line: UInt
+    ) rethrows -> T
+  )
   @available(SwiftStdlib 5.9, *)
   @usableFromInline
   @_unavailableInEmbedded
-  @_silgen_name("$sScAsE14assumeIsolated_4file4lineqd__qd__xYiKXE_s12StaticStringVSutKlF")
-  internal nonisolated func __abi__assumeIsolated<T : Sendable>(
+  internal nonisolated func __nonsendable_assumeIsolated<T : Sendable>(
       _ operation: (isolated Self) throws -> T,
       _ file: StaticString, _ line: UInt
   ) rethrows -> T {

Diff for: stdlib/public/Concurrency/MainActor.swift

@@ -148,10 +148,15 @@ extension MainActor {
     }
   }
 
+  @abi(
+    static func assumeIsolated<T /* not ': Sendable' */>(
+        _ operation: @MainActor () throws -> T,
+        file: StaticString, line: UInt
+    ) rethrows -> T
+  )
   @available(SwiftStdlib 5.9, *)
   @usableFromInline
-  @_silgen_name("$sScM14assumeIsolated_4file4linexxyKScMYcXE_s12StaticStringVSutKlFZ")
-  internal static func __abi__assumeIsolated<T : Sendable>(
+  internal static func __nonsendable_assumeIsolated<T : Sendable>(
       _ operation: @MainActor () throws -> T,
       _ file: StaticString, _ line: UInt
   ) rethrows -> T {

Diff for: stdlib/public/Concurrency/Task+TaskExecutor.swift

@@ -164,10 +164,15 @@ public func withTaskExecutorPreference<T, Failure>(
 //
 // This function also doubles as an ABI-compatibility shim predating the
 // introduction of #isolation.
+@abi(
+  func withTaskExecutorPreference<T: Sendable>(
+    _ taskExecutor: (any TaskExecutor)?,
+    operation: @Sendable () async throws -> T
+  ) async rethrows -> T
+)
 @_unavailableInEmbedded
 @available(SwiftStdlib 6.0, *)
 @_unsafeInheritExecutor // for ABI compatibility
-@_silgen_name("$ss26withTaskExecutorPreference_9operationxSch_pSg_xyYaYbKXEtYaKs8SendableRzlF")
 public func _unsafeInheritExecutor_withTaskExecutorPreference<T: Sendable>(
   _ taskExecutor: (any TaskExecutor)?,
   operation: @Sendable () async throws -> T

Diff for: stdlib/public/Concurrency/TaskCancellation.swift

@@ -89,9 +89,14 @@ public func withTaskCancellationHandler<T>(
 //
 // This function also doubles as an ABI-compatibility shim predating the
 // introduction of #isolation.
+@abi(
+  func withTaskCancellationHandler<T>(
+    operation: () async throws -> T,
+    onCancel handler: @Sendable () -> Void
+  ) async rethrows -> T
+)
 @_unsafeInheritExecutor // ABI compatibility with Swift 5.1
 @available(SwiftStdlib 5.1, *)
-@_silgen_name("$ss27withTaskCancellationHandler9operation8onCancelxxyYaKXE_yyYbXEtYaKlF")
 public func _unsafeInheritExecutor_withTaskCancellationHandler<T>(
   operation: () async throws -> T,
   onCancel handler: @Sendable () -> Void

Diff for: stdlib/public/Concurrency/TaskGroup.swift

@@ -97,8 +97,15 @@ public func withTaskGroup<ChildTaskResult, GroupResult>(
 //
 // This function also doubles as an ABI-compatibility shim predating the
 // introduction of #isolation.
+@abi(
+  @preconcurrency   // TaskGroup.ChildTaskResult: Sendable
+  func withTaskGroup<ChildTaskResult, GroupResult>(
+    of childTaskResultType: ChildTaskResult.Type,
+    returning returnType: GroupResult.Type,
+    body: (inout TaskGroup<ChildTaskResult>) async -> GroupResult
+  ) async -> GroupResult
+)
 @available(SwiftStdlib 5.1, *)
-@_silgen_name("$ss13withTaskGroup2of9returning4bodyq_xm_q_mq_ScGyxGzYaXEtYar0_lF")
 @_unsafeInheritExecutor // for ABI compatibility
 @inlinable
 public func _unsafeInheritExecutor_withTaskGroup<ChildTaskResult, GroupResult>(
@@ -243,8 +250,15 @@ public func withThrowingTaskGroup<ChildTaskResult, GroupResult>(
 //
 // This function also doubles as an ABI-compatibility shim predating the
 // introduction of #isolation.
+@abi(
+  @preconcurrency   // ThrowingTaskGroup.ChildTaskResult: Sendable
+  func withThrowingTaskGroup<ChildTaskResult, GroupResult>(
+    of childTaskResultType: ChildTaskResult.Type,
+    returning returnType: GroupResult.Type,
+    body: (inout ThrowingTaskGroup<ChildTaskResult, Error>) async throws -> GroupResult
+  ) async rethrows -> GroupResult
+)
 @available(SwiftStdlib 5.1, *)
-@_silgen_name("$ss21withThrowingTaskGroup2of9returning4bodyq_xm_q_mq_Scgyxs5Error_pGzYaKXEtYaKr0_lF")
 @_unsafeInheritExecutor // for ABI compatibility
 public func _unsafeInheritExecutor_withThrowingTaskGroup<ChildTaskResult, GroupResult>(
   of childTaskResultType: ChildTaskResult.Type,
@@ -690,7 +704,7 @@ public struct ThrowingTaskGroup<ChildTaskResult: Sendable, Failure: Error> {
     return try await _taskGroupWaitNext(group: _group)
   }
 
-  @_silgen_name("$sScg10nextResults0B0Oyxq_GSgyYaKF")
+  @abi(mutating func nextResult() async throws -> Result<ChildTaskResult, Failure>?)
   @usableFromInline
   mutating func nextResultForABI() async throws -> Result<ChildTaskResult, Failure>? {
     do {

Diff for: stdlib/public/Concurrency/TaskLocal.swift

@@ -221,10 +221,16 @@ public final class TaskLocal<Value: Sendable>: Sendable, CustomStringConvertible
   //
   // This function also doubles as an ABI-compatibility shim predating the
   // introduction of #isolation.
+  @abi(
+    func withValue<R>(
+      _ valueDuringOperation: Value,
+      operation: () async throws -> R,
+      file: String, line: UInt
+    ) async rethrows -> R
+  )
   @discardableResult
   @_unsafeInheritExecutor // ABI compatibility with Swift 5.1
   @available(SwiftStdlib 5.1, *)
-  @_silgen_name("$ss9TaskLocalC9withValue_9operation4file4lineqd__x_qd__yYaKXESSSutYaKlF")
   public func _unsafeInheritExecutor_withValue<R>(
     _ valueDuringOperation: Value,
     operation: () async throws -> R,
@@ -265,7 +271,13 @@ public final class TaskLocal<Value: Sendable>: Sendable, CustomStringConvertible
     return try await operation()
   }
 
-  @_silgen_name("$ss9TaskLocalC13withValueImpl_9operation4file4lineqd__xn_qd__yYaKXESSSutYaKlF")
+  @abi(
+    func withValueImpl<R>(
+      _ valueDuringOperation: __owned Value,
+      operation: () async throws -> R,
+      file: String, line: UInt
+    ) async rethrows -> R
+  )
   @inlinable
   @discardableResult
   @_unsafeInheritExecutor // internal for backwards compatibility; though may be able to be removed safely?

Diff for: stdlib/public/Distributed/DistributedActor.swift

@@ -362,10 +362,15 @@ extension DistributedActor {
   /// state.
   ///
   /// When the actor is remote, the closure won't be executed and this function will return nil.
+  @abi(
+    // We need to @abi here because the signature is the same as
+    // `__separately_compiled_typed_throws_whenLocal(_:)`, and even though this
+    // is @AEIC, the symbol name would conflict.
+    nonisolated func __typed_throws_whenLocal<T: Sendable, E>(
+      _ body: @Sendable (isolated Self) async throws(E) -> T
+    ) async throws(E) -> T?
+  )
   @_alwaysEmitIntoClient
-  // we need to silgen_name here because the signature is the same as __abi_whenLocal,
-  // and even though this is @AEIC, the symbol name would conflict.
-  @_silgen_name("$s11Distributed0A5ActorPAAE20whenLocalTypedThrowsyqd__Sgqd__xYiYaYbqd_0_YKXEYaqd_0_YKs8SendableRd__s5ErrorRd_0_r0_lF")
   public nonisolated func whenLocal<T: Sendable, E>(
     _ body: @Sendable (isolated Self) async throws(E) -> T
   ) async throws(E) -> T? {
@@ -380,18 +385,26 @@ extension DistributedActor {
   // ABI: This is a workaround when in Swift 6 this method was introduced
   // in order to support typed-throws, but missed to add @_aeic.
   // In practice, this method should not ever be used by anyone, ever.
+  @abi(
+    nonisolated func whenLocal<T: Sendable, E>(
+      _ body: @Sendable (isolated Self) async throws(E) -> T
+    ) async throws(E) -> T?
+  )
   @usableFromInline
-  @_silgen_name("$s11Distributed0A5ActorPAAE9whenLocalyqd__Sgqd__xYiYaYbqd_0_YKXEYaqd_0_YKs8SendableRd__s5ErrorRd_0_r0_lF")
-  internal nonisolated func __abi_whenLocal<T: Sendable, E>(
+  nonisolated func __separately_compiled_typed_throws_whenLocal<T: Sendable, E>(
     _ body: @Sendable (isolated Self) async throws(E) -> T
   ) async throws(E) -> T? {
     try await whenLocal(body)
   }
 
   // ABI: Historical whenLocal, rethrows was changed to typed throws `throws(E)`
-  @_silgen_name("$s11Distributed0A5ActorPAAE9whenLocalyqd__Sgqd__xYiYaYbKXEYaKs8SendableRd__lF")
+  @abi(
+    nonisolated func whenLocal<T: Sendable>(
+      _ body: @Sendable (isolated Self) async throws -> T
+    ) async rethrows -> T?
+  )
   @usableFromInline
-  nonisolated func __abi_whenLocal<T: Sendable>(
+  nonisolated func __rethrows_whenLocal<T: Sendable>(
     _ body: @Sendable (isolated Self) async throws -> T
   ) async rethrows -> T? {
     try await whenLocal(body)

Diff for: stdlib/public/Distributed/DistributedAssertions.swift

@@ -179,10 +179,15 @@ extension DistributedActor {
     }
   }
 
+  @abi(
+    nonisolated func assumeIsolated<T /* not ': Sendable' */>(
+      _ operation: (isolated Self) throws -> T,
+      file: StaticString, line: UInt
+    ) rethrows -> T
+  )
   @available(SwiftStdlib 5.9, *)
   @usableFromInline
-  @_silgen_name("$s11Distributed0A5ActorPAAE14assumeIsolated_4file4lineqd__qd__xYiKXE_s12StaticStringVSutKlF")
-  internal nonisolated func __abi__assumeIsolated<T : Sendable>(
+  internal nonisolated func __nonsendable_assumeIsolated<T : Sendable>(
       _ operation: (isolated Self) throws -> T,
       _ file: StaticString, _ line: UInt
   ) rethrows -> T {

Diff for: stdlib/public/core/Array.swift

@@ -1613,12 +1613,16 @@ extension Array {
 
   // Superseded by the typed-throws version of this function, but retained
   // for ABI reasons.
+  @abi(
+    mutating func withUnsafeMutableBufferPointer<R>(
+      _ body: (inout UnsafeMutableBufferPointer<Element>) throws -> R
+    ) rethrows -> R
+  )
   @_semantics("array.withUnsafeMutableBufferPointer")
   @_effects(notEscaping self.value**)
   @usableFromInline
   @inline(__always)
-  @_silgen_name("$sSa30withUnsafeMutableBufferPointeryqd__qd__SryxGzKXEKlF")
-  mutating func __abi_withUnsafeMutableBufferPointer<R>(
+  mutating func __rethrows_withUnsafeMutableBufferPointer<R>(
     _ body: (inout UnsafeMutableBufferPointer<Element>) throws -> R
   ) rethrows -> R {
     _makeMutableAndUnique()

Diff for: stdlib/public/core/ArrayBuffer.swift

@@ -646,9 +646,13 @@ extension _ArrayBuffer {
   /// created on-demand.
   // Superseded by the typed-throws version of this function, but retained
   // for ABI reasons.
+  @abi(
+    func withUnsafeBufferPointer<R>(
+      _ body: (UnsafeBufferPointer<Element>) throws -> R
+    ) rethrows -> R
+  )
   @usableFromInline
-  @_silgen_name("$ss12_ArrayBufferV010withUnsafeB7Pointeryqd__qd__SRyxGKXEKlF")
-  internal func __abi_withUnsafeBufferPointer<R>(
+  internal func __rethrows_withUnsafeBufferPointer<R>(
     _ body: (UnsafeBufferPointer<Element>) throws -> R
   ) rethrows -> R {
     if _fastPath(_isNative) {
@@ -676,9 +680,13 @@ extension _ArrayBuffer {
 
   // Superseded by the typed-throws version of this function, but retained
   // for ABI reasons.
+  @abi(
+    mutating func withUnsafeMutableBufferPointer<R>(
+      _ body: (UnsafeMutableBufferPointer<Element>) throws -> R
+    ) rethrows -> R
+  )
   @usableFromInline
-  @_silgen_name("$ss12_ArrayBufferV017withUnsafeMutableB7Pointeryqd__qd__SryxGKXEKlF")
-  internal mutating func __abi_withUnsafeMutableBufferPointer<R>(
+  internal mutating func __rethrows_withUnsafeMutableBufferPointer<R>(
     _ body: (UnsafeMutableBufferPointer<Element>) throws -> R
   ) rethrows -> R {
     return try unsafe withUnsafeMutableBufferPointer(body)