Frontend: Introduce an alias for the IsolatedAny experimental feature.

To preserve compatibility with older compilers that do not allow `IsolatedAny`
to be enabled in production compilers, use an alias experimental feature when
building the stdlib (`IsolatedAny2`).

Also, add `@_allowFeatureSuppression(IsolatedAny)` in a couple spots it was
forgotten.

Partially resolves rdar://125138945

Author: tshortli

include/swift/Basic/Features.def

@@ -361,6 +361,9 @@ EXPERIMENTAL_FEATURE(ClosureIsolation, true)
 // Enable isolated(any) attribute on function types.
 CONDITIONALLY_SUPPRESSIBLE_EXPERIMENTAL_FEATURE(IsolatedAny, true)
 
+// Alias for IsolatedAny
+EXPERIMENTAL_FEATURE(IsolatedAny2, true)
+
 // Enable usability improvements for global-actor-isolated types.
 EXPERIMENTAL_FEATURE(GlobalActorIsolatedTypesUsability, false)
 

lib/AST/FeatureSet.cpp

@@ -681,6 +681,8 @@ static bool usesFeatureIsolatedAny(Decl *decl) {
   });
 }
 
+UNINTERESTING_FEATURE(IsolatedAny2)
+
 static bool usesFeatureGlobalActorIsolatedTypesUsability(Decl *decl) {
   return false;
 }

lib/Frontend/CompilerInvocation.cpp

@@ -886,6 +886,9 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
 
       if (*feature == Feature::NoncopyableGenerics2)
         Opts.enableFeature(Feature::NoncopyableGenerics);
+
+      if (*feature == Feature::IsolatedAny2)
+        Opts.enableFeature(Feature::IsolatedAny);
     }
 
     // Hack: In order to support using availability macros in SPM packages, we

stdlib/public/Concurrency/CMakeLists.txt

@@ -62,7 +62,7 @@ endif()
 
 list(APPEND SWIFT_RUNTIME_CONCURRENCY_SWIFT_FLAGS
   "-enable-experimental-feature"
-  "IsolatedAny"
+  "IsolatedAny2"
 )
 
 list(APPEND SWIFT_RUNTIME_CONCURRENCY_C_FLAGS

stdlib/public/Concurrency/TaskGroup.swift

@@ -782,6 +782,7 @@ public struct ThrowingTaskGroup<ChildTaskResult: Sendable, Failure: Error> {
   ///     to set the child task's priority to the priority of the group.
   ///   - operation: The operation to execute as part of the task group.
   @_alwaysEmitIntoClient
+  @_allowFeatureSuppression(IsolatedAny)
   public mutating func addTask(
     priority: TaskPriority? = nil,
     operation: __owned @Sendable @escaping @isolated(any) () async throws -> ChildTaskResult
@@ -823,6 +824,7 @@ public struct ThrowingTaskGroup<ChildTaskResult: Sendable, Failure: Error> {
   /// - Returns: `true` if the child task was added to the group;
   ///   otherwise `false`.
   @_alwaysEmitIntoClient
+  @_allowFeatureSuppression(IsolatedAny)
   public mutating func addTaskUnlessCancelled(
     priority: TaskPriority? = nil,
     operation: __owned @Sendable @escaping @isolated(any) () async throws -> ChildTaskResult

test/ModuleInterface/isolated_any_suppression.swift

@@ -1,6 +1,7 @@
 // RUN: %empty-directory(%t)
 
 // RUN: %target-swift-frontend -swift-version 5 -enable-library-evolution -module-name isolated_any -emit-module -o %t/isolated_any.swiftmodule -emit-module-interface-path -  -enable-experimental-feature IsolatedAny %s | %FileCheck %s
+// RUN: %target-swift-frontend -swift-version 5 -enable-library-evolution -module-name isolated_any -emit-module -o %t/isolated_any.swiftmodule -emit-module-interface-path -  -enable-experimental-feature IsolatedAny2 %s | %FileCheck %s
 
 // CHECK:      #if compiler(>=5.3) && $IsolatedAny
 // CHECK-NEXT: {{^}}public func test1(fn: @isolated(any) @Sendable () -> ())