[SE-0313] Hop to the exector if an async function with an isolated parameter

Author: DougGregor

lib/SILGen/SILGenProlog.cpp

@@ -503,6 +503,25 @@ void SILGenFunction::emitProlog(CaptureInfo captureInfo,
     switch (actorIsolation.getKind()) {
       case ActorIsolation::Unspecified:
       case ActorIsolation::Independent:
+        // If this is an async function that has an isolated parameter, hop
+        // to it.
+        if (F.isAsync()) {
+          for (auto param : *funcDecl->getParameters()) {
+            if (param->isIsolated()) {
+              auto loc = RegularLocation::getAutoGeneratedLocation(F.getLocation());
+              Type actorType = param->getType();
+              RValue actorInstanceRV = emitRValueForDecl(
+                  loc, param, actorType, AccessSemantics::Ordinary);
+              ManagedValue actorInstance =
+                  std::move(actorInstanceRV).getScalarValue();
+              ExpectedExecutor = emitLoadActorExecutor(loc, actorInstance);
+              break;
+            }
+          }
+        }
+
+        break;
+
       case ActorIsolation::GlobalActorUnsafe:
         break;
 

test/SILGen/hop_to_executor.swift

@@ -381,3 +381,11 @@ func testImplicitAsyncIsolatedParam(
   // CHECK-NEXT: hop_to_executor [[CURRENT]] : $Optional<Builtin.Executor>
   await otherActor.otherIsolated(i, actor, d)
 }
+
+// CHECK-LABEL: sil hidden [ossa] @$s4test22asyncWithIsolatedParam1i5actor1dySi_AA7MyActorCYiSdtYaF : $@convention(thin) @async (Int, @guaranteed MyActor, Double) -> ()
+func asyncWithIsolatedParam(i: Int, actor: isolated MyActor, d: Double) async {
+  // CHECK: [[ACTOR:%.*]] = copy_value %1 : $MyActor
+  // CHECK-NEXT: [[BORROWED:%.*]] = begin_borrow [[ACTOR]] : $MyActor
+  // CHECK-NEXT: hop_to_executor [[BORROWED]] : $MyActor
+  // CHECK-NEXT: end_borrow [[BORROWED]] : $MyActor
+}