元コードはこうなんだよな

public func withSpan<T>( _ operationName: String, context: @autoclosure () -> ServiceContext = .current ?? .topLevel, ofKind kind: SpanKind = .internal, isolation: isolated (any Actor)? = #isolation, function: String = #function, file fileID: String = #fileID, line: UInt = #line, _ operation: (any Span) async throws -> T ) async rethrows -> T { try await InstrumentationSystem.legacyTracer.withAnySpan( operationName, at: DefaultTracerClock.now, context: context(), ofKind: kind, function: function, file: fileID, line: line ) { anySpan in try await operation(anySpan) } }

3:41 AM

try await operation(anySpan) をむき出しにするとエラーになる

3:42 AM

内側はこうで、これもまた包まれてる

 public func withAnySpan<T, Instant: TracerInstant>( _ operationName: String, at instant: @autoclosure () -> Instant, context: @autoclosure () -> ServiceContext = .current ?? .topLevel, ofKind kind: SpanKind = .internal, isolation: isolated (any Actor)? = #isolation, function: String = #function, file fileID: String = #fileID, line: UInt = #line, _ operation: (any Tracing.Span) async throws -> T ) async rethrows -> T { let span = self.startAnySpan( operationName, at: instant(), context: context(), ofKind: kind, function: function, file: fileID, line: line ) defer { span.end() } do { return try await ServiceContext.$current.withValue(span.context) { try await operation(span) } } catch { span.recordError(error) throw error // rethrow } }

3:43 AM

 @inlinable final public func withValue<R>(_ valueDuringOperation: Value, operation: () async throws -> R, isolation: isolated (any Actor)? = #isolation, file: String = #fileID, line: UInt = #line) async rethrows -> R

3:43 AM

withValueも同じ形だけどこれはstdlibだからわからない

3:44 AM

 internal func withValueImpl<R>(_ valueDuringOperation: __owned Value, operation: () async throws -> R, isolation: isolated (any Actor)?, file: String = #fileID, line: UInt = #line) async rethrows -> R { _taskLocalValuePush(key: key, value: consume valueDuringOperation) defer { _taskLocalValuePop() } return try await operation() }

3:46 AM

@swift-6.1-dev

func withValueImpl<R>( operation: () async throws -> R, isolation: isolated (any Actor)? ) async rethrows -> R { return try await operation() }