Address code review feedback and fix rebase typo in a test

Author: DougGregor

lib/Sema/TypeCheckConcurrency.cpp

@@ -3892,6 +3892,10 @@ namespace {
 
     void recordCurrentContextIsolation(
         CurrentContextIsolationExpr *isolationExpr) {
+      // If an actor has already been assigned, we're done.
+      if (isolationExpr->getActor())
+        return;
+
       // #isolation does not work within an `@_unsafeInheritExecutor` function.
       if (auto func = enclosingUnsafeInheritsExecutor(getDeclContext())) {
         // This expression is always written as a macro #isolation in source,
@@ -3909,10 +3913,6 @@ namespace {
         replaceUnsafeInheritExecutorWithDefaultedIsolationParam(func, diag);
       }
 
-      // If an actor has already been assigned, we're done.
-      if (isolationExpr->getActor())
-        return;
-
       auto loc = isolationExpr->getLoc();
       auto isolation = getActorIsolationOfContext(
           const_cast<DeclContext *>(getDeclContext()),

stdlib/public/Concurrency/CheckedContinuation.swift

@@ -299,6 +299,12 @@ public func withCheckedContinuation<T>(
   }
 }
 
+// Note: hack to stage out @_unsafeInheritExecutor forms of various functions
+// in favor of #isolation. The _unsafeInheritExecutor_ prefix is meaningful
+// to the type checker.
+//
+// This function also doubles as an ABI-compatibility shim predating the
+// introduction of #isolation.
 @available(SwiftStdlib 5.1, *)
 @_unsafeInheritExecutor // ABI compatibility with Swift 5.1
 @_unavailableInEmbedded
@@ -359,6 +365,12 @@ public func withCheckedThrowingContinuation<T>(
   }
 }
 
+// Note: hack to stage out @_unsafeInheritExecutor forms of various functions
+// in favor of #isolation. The _unsafeInheritExecutor_ prefix is meaningful
+// to the type checker.
+//
+// This function also doubles as an ABI-compatibility shim predating the
+// introduction of #isolation.
 @available(SwiftStdlib 5.1, *)
 @_unsafeInheritExecutor // ABI compatibility with Swift 5.1
 @_unavailableInEmbedded

stdlib/public/Concurrency/PartialAsyncTask.swift

@@ -730,21 +730,23 @@ public func withUnsafeThrowingContinuation<T>(
   }
 }
 
-// HACK: a version of withUnsafeContinuation that uses the unsafe
-// @_unsafeInheritExecutor.
+// Note: hack to stage out @_unsafeInheritExecutor forms of various functions
+// in favor of #isolation. The _unsafeInheritExecutor_ prefix is meaningful
+// to the type checker.
 @available(SwiftStdlib 5.1, *)
 @_alwaysEmitIntoClient
 @_unsafeInheritExecutor
 public func _unsafeInheritExecutor_withUnsafeContinuation<T>(
   _ fn: (UnsafeContinuation<T, Never>) -> Void
-) async -> T {
+) async -> sending T {
   return await Builtin.withUnsafeContinuation {
     fn(UnsafeContinuation<T, Never>($0))
   }
 }
 
-// HACK: a version of withUnsafeThrowingContinuation that uses the unsafe
-// @_unsafeInheritExecutor.
+// Note: hack to stage out @_unsafeInheritExecutor forms of various functions
+// in favor of #isolation. The _unsafeInheritExecutor_ prefix is meaningful
+// to the type checker.
 @available(SwiftStdlib 5.1, *)
 @_alwaysEmitIntoClient
 @_unsafeInheritExecutor

stdlib/public/Concurrency/SourceCompatibilityShims.swift

@@ -62,6 +62,9 @@ public func withTaskCancellationHandler<T>(
   try await withTaskCancellationHandler(operation: operation, onCancel: handler)
 }
 
+// Note: hack to stage out @_unsafeInheritExecutor forms of various functions
+// in favor of #isolation. The _unsafeInheritExecutor_ prefix is meaningful
+// to the type checker.
 @available(SwiftStdlib 5.1, *)
 @_alwaysEmitIntoClient
 @_unsafeInheritExecutor

stdlib/public/Concurrency/TaskCancellation.swift

@@ -82,6 +82,12 @@ public func withTaskCancellationHandler<T>(
   return try await operation()
 }
 
+// Note: hack to stage out @_unsafeInheritExecutor forms of various functions
+// in favor of #isolation. The _unsafeInheritExecutor_ prefix is meaningful
+// to the type checker.
+//
+// This function also doubles as an ABI-compatibility shim predating the
+// introduction of #isolation.
 @_unsafeInheritExecutor // ABI compatibility with Swift 5.1
 @available(SwiftStdlib 5.1, *)
 @_silgen_name("$ss27withTaskCancellationHandler9operation8onCancelxxyYaKXE_yyYbXEtYaKlF")

test/Concurrency/unsafe_inherit_executor.swift

@@ -53,7 +53,6 @@ func unsafeCallerA(x: Int) async {
 
   await inheritsIsolationProperly()
   // expected-error@-1{{#isolation (introduced by a default argument) cannot be used within an '@_unsafeInheritExecutor' function}}{{50:1-24=}}{{51:26-26=, isolation: isolated (any Actor)? = #isolation}}
-t 6)
 }
 
 @_unsafeInheritExecutor