Executor.swift: only enable MainActor in Embedded Swift for WASI

Author: MaxDesiatov

stdlib/public/Concurrency/Executor.swift

@@ -36,9 +36,11 @@ public protocol Executor: AnyObject, Sendable {
   func enqueue(_ job: consuming ExecutorJob)
   #endif // !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY
 
+  #if os(WASI) || !$Embedded
   /// `true` if this is the main executor.
   @available(StdlibDeploymentTarget 6.2, *)
   var isMainExecutor: Bool { get }
+  #endif // os(WASI) || !$Embedded
 }
 
 @available(StdlibDeploymentTarget 6.2, *)
@@ -142,11 +144,12 @@ extension Executor where Self: Equatable {
 }
 
 extension Executor {
-
+  #if os(WASI) || !$Embedded
   // This defaults to `false` so that existing third-party Executor
   // implementations will work as expected.
   @available(StdlibDeploymentTarget 6.2, *)
   public var isMainExecutor: Bool { false }
+  #endif // os(WASI) || !$Embedded
 
 }
 
@@ -364,10 +367,10 @@ public protocol SerialExecutor: Executor {
 @available(StdlibDeploymentTarget 6.0, *)
 extension SerialExecutor {
 
-  #if !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY
+  #if os(WASI) || (!$Embedded && !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY)
   @available(StdlibDeploymentTarget 6.2, *)
   public var isMainExecutor: Bool { return MainActor.executor._isSameExecutor(self) }
-  #endif
+  #endif // os(WASI) || (!$Embedded && !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY)
 
   @available(StdlibDeploymentTarget 6.0, *)
   public func checkIsolated() {
@@ -575,9 +578,11 @@ public protocol MainExecutor: RunLoopExecutor, SerialExecutor {
 /// executors.
 @available(StdlibDeploymentTarget 6.2, *)
 public protocol ExecutorFactory {
+  #if os(WASI) || !$Embedded
   /// Constructs and returns the main executor, which is started implicitly
   /// by the `async main` entry point and owns the "main" thread.
   static var mainExecutor: any MainExecutor { get }
+  #endif // os(WASI) || !$Embedded
 
   /// Constructs and returns the default or global executor, which is the
   /// default place in which we run tasks.
@@ -590,9 +595,9 @@ typealias DefaultExecutorFactory = PlatformExecutorFactory
 @available(StdlibDeploymentTarget 6.2, *)
 @_silgen_name("swift_createExecutors")
 public func _createExecutors<F: ExecutorFactory>(factory: F.Type) {
-  #if !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY
+  #if os(WASI) || (!$Embedded && !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY)
   MainActor._executor = factory.mainExecutor
-  #endif
+  #endif // os(WASI) || (!$Embedded && !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY)
   Task._defaultExecutor = factory.defaultExecutor
 }