[Concurrency] NonisolatedNonsendingByDefault: Turn inferred nonisolated into nonisolated(nonsending)

Inferred `nonisolated` from the context i.e. an extension should
mark the member as `@concurrent` instead it should behave as
`nonisolated(nonsending)` when `NonisolatedNonsendingByDefault`
is enabled.

Resolves: rdar://157789572

Author: xedin

lib/Sema/TypeCheckConcurrency.cpp

@@ -6513,6 +6513,14 @@ static InferredActorIsolation computeActorIsolation(Evaluator &evaluator,
       }
     }
 
+    // When `NonisolatedNonsendingByDefault` feature is enabled and the value is
+    // asynchronous `nonisolated` always means `nonisolated(nonsending)`.
+    if (ctx.LangOpts.hasFeature(Feature::NonisolatedNonsendingByDefault) &&
+        value->getModuleContext() == ctx.MainModule &&
+        inferred.isNonisolated() && value->isAsync()) {
+      inferred = ActorIsolation::forCallerIsolationInheriting();
+    }
+
     // Add an implicit attribute to capture the actor isolation that was
     // inferred, so that (e.g.) it will be printed and serialized.
     switch (inferred) {
@@ -6724,13 +6732,6 @@ static InferredActorIsolation computeActorIsolation(Evaluator &evaluator,
       if (shouldSelfIsolationOverrideDefault(
               ctx, value->getDeclContext(), selfTypeIsolation.isolation)) {
         auto isolation = selfTypeIsolation.isolation;
-
-        if (ctx.LangOpts.hasFeature(Feature::NonisolatedNonsendingByDefault) &&
-            value->isAsync() && value->getModuleContext() == ctx.MainModule &&
-            isolation.isNonisolated()) {
-          isolation = ActorIsolation::forCallerIsolationInheriting();
-        }
-
         return {inferredIsolation(isolation, onlyGlobal),
                 selfTypeIsolation.source};
       }

test/Concurrency/attr_execution/nonisolated_cross_module_with_flag_enabled.swift

@@ -47,6 +47,36 @@ public struct InferenceTest {
   public func testAutoclosure(value2 fn: nonisolated(nonsending) @autoclosure () async -> Int) async { await fn() }
 }
 
+// CHECK: nonisolated extension A.InferenceTest {
+// CHECK:   nonisolated(nonsending) public func testInExtension() async
+// CHECK:   @concurrent public func testConcurrentInExtension() async
+// CHECK: }
+nonisolated public extension InferenceTest {
+  func testInExtension() async {}
+  @concurrent func testConcurrentInExtension() async {}
+}
+
+// CHECK: public protocol P {
+// CHECK:   nonisolated(nonsending) func testWitness() async
+// CHECK: }
+public protocol P {
+  func testWitness() async
+}
+
+// CHECK: public struct WitnessTest : nonisolated A.P {
+// CHECK:   nonisolated(nonsending) public func testWitness() async
+// CHECK: }
+public struct WitnessTest: nonisolated P {
+  public func testWitness() async {}
+}
+
+// CHECK: nonisolated public class NoinsolatedClassTest {
+// CHECK:   nonisolated(nonsending) public func test() async
+// CHECK: }
+nonisolated public class NoinsolatedClassTest {
+  public func test() async {}
+}
+
 //--- Client.swift
 import A
 
@@ -75,13 +105,18 @@ func testWithCallback(t: Test) async {
 // CHECK: function_ref @$s1A13InferenceTestV10infersAttryyYaF : $@convention(method) @async (@sil_isolated @sil_implicit_leading_param @guaranteed Builtin.ImplicitActor, @in_guaranteed InferenceTest) -> ()
 // CHECK: function_ref @$s1A13InferenceTestV10testNested8callbackyyyyYaYbYCXEc_tF : $@convention(method) (@guaranteed @callee_guaranteed (@guaranteed @noescape @Sendable @async @callee_guaranteed (@sil_isolated @sil_implicit_leading_param @guaranteed Builtin.ImplicitActor) -> ()) -> (), @in_guaranteed InferenceTest) -> ()
 // CHECK: function_ref @$s1A13InferenceTestV10testNested4dictySDySSyyYaYCcSgG_tF : $@convention(method) (@guaranteed Dictionary<String, Optional<nonisolated(nonsending) () async -> ()>>, @in_guaranteed InferenceTest) -> ()
+// CHECK: function_ref @$s1A13InferenceTestV15testInExtensionyyYaF : $@convention(method) @async (@sil_isolated @sil_implicit_leading_param @guaranteed Builtin.ImplicitActor, @in_guaranteed InferenceTest) -> ()
+// CHECK: function_ref @$s1A13InferenceTestV25testConcurrentInExtensionyyYaF : $@convention(method) @async (@in_guaranteed InferenceTest) -> ()
 // CHECK: } // end sil function '$s6Client13testInference1ty1A0C4TestV_tYaF'
 @MainActor
 func testInference(t: InferenceTest) async {
     await t.infersAttr()
 
     t.testNested { _ in }
     t.testNested(dict: [:])
+
+    await t.testInExtension()
+    await t.testConcurrentInExtension()
 }
 
 // CHECK-LABEL: sil hidden @$s6Client15testAutoclosure1ty1A13InferenceTestV_tYaF : $@convention(thin) @async (@in_guaranteed InferenceTest) -> ()
@@ -92,3 +127,17 @@ func testAutoclosure(t: InferenceTest) async {
     await t.testAutoclosure(value1: 42)
     await t.testAutoclosure(value2: 42)
 }
+
+// CHECK-LABEL: sil hidden @$s6Client26testWitnessWithNonisolated1ty1A0C4TestV_tYaF : $@convention(thin) @async (@in_guaranteed WitnessTest) -> ()
+// CHECK: function_ref @$s1A11WitnessTestV04testA0yyYaF : $@convention(method) @async (@sil_isolated @sil_implicit_leading_param @guaranteed Builtin.ImplicitActor, @in_guaranteed WitnessTest) -> ()
+// CHECK: } // end sil function '$s6Client26testWitnessWithNonisolated1ty1A0C4TestV_tYaF'
+func testWitnessWithNonisolated(t: WitnessTest) async {
+  await t.testWitness()
+}
+
+// CHECK-LABEL: sil hidden @$s6Client20testNonisolatedClass1ty1A011NoinsolatedD4TestC_tYaF : $@convention(thin) @async (@guaranteed NoinsolatedClassTest) -> ()
+// CHECK: class_method {{.*}}, #NoinsolatedClassTest.test : (NoinsolatedClassTest) -> () async -> (), $@convention(method) @async (@sil_isolated @sil_implicit_leading_param @guaranteed Builtin.ImplicitActor, @guaranteed NoinsolatedClassTest) -> ()
+// CHECK: } // end sil function '$s6Client20testNonisolatedClass1ty1A011NoinsolatedD4TestC_tYaF'
+func testNonisolatedClass(t: NoinsolatedClassTest) async {
+  await t.test()
+}