Concurrency: Promote BuiltinBuildComplexEqualityExecutor feature to baseline.

Author: tshortli

include/swift/Basic/Features.def

@@ -148,7 +148,7 @@ BASELINE_LANGUAGE_FEATURE(InheritActorContext, 0, "@_inheritActorContext attribu
 BASELINE_LANGUAGE_FEATURE(ImplicitSelfCapture, 0, "@_implicitSelfCapture attribute")
 BASELINE_LANGUAGE_FEATURE(BuiltinBuildTaskExecutorRef, 0, "TaskExecutor-building builtins")
 BASELINE_LANGUAGE_FEATURE(BuiltinBuildExecutor, 0, "Executor-building builtins")
-LANGUAGE_FEATURE(BuiltinBuildComplexEqualityExecutor, 0, "Executor-building for 'complexEquality executor' builtins")
+BASELINE_LANGUAGE_FEATURE(BuiltinBuildComplexEqualityExecutor, 0, "Executor-building for 'complexEquality executor' builtins")
 BASELINE_LANGUAGE_FEATURE(BuiltinBuildMainExecutor, 0, "MainActor executor building builtin")
 BASELINE_LANGUAGE_FEATURE(BuiltinCreateAsyncTaskInGroup, 0, "Task create in task group builtin with extra flags")
 LANGUAGE_FEATURE(BuiltinCreateAsyncTaskInGroupWithExecutor, 0, "Task create in task group builtin with extra flags")

lib/AST/FeatureSet.cpp

@@ -124,7 +124,6 @@ static bool usesFeatureRethrowsProtocol(Decl *decl) {
   return usesFeatureRethrowsProtocol(decl, checked);
 }
 
-UNINTERESTING_FEATURE(BuiltinBuildComplexEqualityExecutor)
 UNINTERESTING_FEATURE(BuiltinCreateAsyncTaskInGroupWithExecutor)
 UNINTERESTING_FEATURE(BuiltinCreateAsyncDiscardingTaskInGroup)
 UNINTERESTING_FEATURE(BuiltinCreateAsyncDiscardingTaskInGroupWithExecutor)

stdlib/public/Concurrency/Executor.swift

@@ -360,11 +360,7 @@ public struct UnownedSerialExecutor: Sendable {
   @available(SwiftStdlib 5.9, *)
   @inlinable
   public init<E: SerialExecutor>(complexEquality executor: __shared E) {
-    #if compiler(>=5.9) && $BuiltinBuildComplexEqualityExecutor
     self.executor = Builtin.buildComplexEqualitySerialExecutorRef(executor)
-    #else
-    fatalError("Swift compiler is incompatible with this SDK version")
-    #endif
   }
 
   @_spi(ConcurrencyExecutors)