SIL: Local functions should inherit isolation from context

If the outer context is actor isolated, we need to force a capture the
actor variable, since otherwise it might not appear in the capture list.

Author: slavapestov

lib/SIL/IR/TypeLowering.cpp

@@ -4312,6 +4312,20 @@ TypeConverter::getLoweredLocalCaptures(SILDeclRef fn) {
     PrettyStackTraceAnyFunctionRef("lowering local captures", curFn);
     collectCaptures(curFn.getCaptureInfo());
 
+    if (auto *afd = curFn.getAbstractFunctionDecl()) {
+      // If a local function inherits isolation from the enclosing context,
+      // make sure we capture the isolated parameter, if we haven't already.
+      if (afd->isLocalCapture()) {
+        auto actorIsolation = getActorIsolation(afd);
+        if (actorIsolation.getKind() == ActorIsolation::ActorInstance) {
+          if (auto *var = actorIsolation.getActorInstance()) {
+            assert(isa<ParamDecl>(var));
+            recordCapture(CapturedValue(var, 0, afd->getLoc()));
+          }
+        }
+      }
+    }
+
     // A function's captures also include its default arguments, because
     // when we reference a function we don't track which default arguments
     // are referenced too.

lib/SILGen/SILGenConcurrency.cpp

@@ -107,8 +107,8 @@ void SILGenFunction::emitExpectedExecutor() {
       // completely.
       if (F.isAsync() ||
           (wantDataRaceChecks && funcDecl->isLocalCapture())) {
-        if (auto isolatedParam = funcDecl->getCaptureInfo()
-                .getIsolatedParamCapture()) {
+        auto loweredCaptures = SGM.Types.getLoweredLocalCaptures(SILDeclRef(funcDecl));
+        if (auto isolatedParam = loweredCaptures.getIsolatedParamCapture()) {
           loadExpectedExecutorForLocalVar(isolatedParam);
         } else {
           auto loc = RegularLocation::getAutoGeneratedLocation(F.getLocation());

test/SILGen/local_function_isolation.swift

@@ -0,0 +1,55 @@
+// RUN: %target-swift-frontend -emit-silgen %s -disable-availability-checking | %FileCheck %s
+
+// REQUIRES: concurrency
+
+class NotSendable {}
+
+func callee(_ ns: NotSendable) {}
+
+actor MyActor {
+  func isolatedToSelf(ns: NotSendable) {
+    // CHECK-LABEL: sil private [ossa] @$s24local_function_isolation7MyActorC14isolatedToSelf2nsyAA11NotSendableC_tF08implicitH7CaptureL_yyYaF : $@convention(thin) @async (@guaranteed NotSendable, @sil_isolated @guaranteed MyActor) -> () {
+    func implicitSelfCapture() async {
+
+      // CHECK: [[COPY:%.*]] = copy_value %1 : $MyActor
+      // CHECK-NEXT: [[BORROW:%.*]] = begin_borrow [[COPY]] : $MyActor
+      // CHECK-NEXT: hop_to_executor [[BORROW]] : $MyActor
+
+      // CHECK: [[FN:%.*]] = function_ref @$s24local_function_isolation4testyyYaF : $@convention(thin) @async () -> ()
+      // CHECK-NEXT: apply [[FN]]() : $@convention(thin) @async () -> ()
+      await test()
+
+      // CHECK: hop_to_executor [[BORROW]] : $MyActor
+      // CHECK: [[FN:%.*]] = function_ref @$s24local_function_isolation6calleeyyAA11NotSendableCF : $@convention(thin) (@guaranteed NotSendable) -> ()
+      // CHECK-NEXT: apply [[FN]](%0) : $@convention(thin) (@guaranteed NotSendable) -> ()
+
+      // we need to hop back to 'self' here
+      callee(ns)
+
+      // CHECK: end_borrow [[BORROW]] : $MyActor
+      // CHECK-NEXT: destroy_value [[COPY]] : $MyActor
+    }
+  }
+}
+
+func f(isolation: isolated MyActor, ns: NotSendable) {
+  // CHECK-LABEL: sil private [ossa] @$s24local_function_isolation1f0C02nsyAA7MyActorCYi_AA11NotSendableCtF23implicitIsolatedCaptureL_yyYaF : $@convention(thin) @async (@guaranteed NotSendable, @sil_isolated @guaranteed MyActor) -> () {
+  func implicitIsolatedCapture() async {
+
+    // CHECK: [[COPY:%.*]] = copy_value %1 : $MyActor
+    // CHECK-NEXT: [[BORROW:%.*]] = begin_borrow [[COPY]] : $MyActor
+    // CHECK-NEXT: hop_to_executor [[BORROW]] : $MyActor
+
+    // CHECK: [[FN:%.*]] = function_ref @$s24local_function_isolation4testyyYaF : $@convention(thin) @async () -> ()
+    // CHECK-NEXT: apply [[FN]]() : $@convention(thin) @async () -> ()
+    await test()
+
+    // we need to hop back to 'isolation' here
+    callee(ns)
+
+    // CHECK: end_borrow [[BORROW]] : $MyActor
+    // CHECK-NEXT: destroy_value [[COPY]] : $MyActor
+  }
+}
+
+func test() async {}