Ensure that Sendable is inherited properly, take 3.

Extend the implicit Sendable request to produce an inherited
conformance when queried, rather than depending on the conformance
lookup table to always have the right entries. This acknowledges that
implicit Sendable needs to happen more at the type checking level than
the name-binding level, which is needed to eliminate cyclic
dependencies.

Author: DougGregor

include/swift/AST/TypeCheckRequests.h

@@ -3095,15 +3095,15 @@ class SynthesizeMainFunctionRequest
 /// the Sendable protocol.
 class GetImplicitSendableRequest :
     public SimpleRequest<GetImplicitSendableRequest,
-                         NormalProtocolConformance *(NominalTypeDecl *),
+                         ProtocolConformance *(NominalTypeDecl *),
                          RequestFlags::Cached> {
 public:
   using SimpleRequest::SimpleRequest;
 
 private:
   friend SimpleRequest;
 
-  NormalProtocolConformance *evaluate(
+  ProtocolConformance *evaluate(
       Evaluator &evaluator, NominalTypeDecl *nominal) const;
 
 public:

include/swift/AST/TypeCheckerTypeIDZone.def

@@ -354,7 +354,7 @@ SWIFT_REQUEST(TypeChecker, SimpleDidSetRequest,
 SWIFT_REQUEST(TypeChecker, SynthesizeMainFunctionRequest,
               FuncDecl *(Decl *), Cached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, GetImplicitSendableRequest,
-              NormalProtocolConformance *(NominalTypeDecl *),
+              ProtocolConformance *(NominalTypeDecl *),
               Cached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, RenamedDeclRequest,
               ValueDecl *(const ValueDecl *),

lib/Sema/TypeCheckConcurrency.cpp

@@ -3855,7 +3855,7 @@ bool swift::checkSendableConformance(
   return checkSendableInstanceStorage(nominal, conformanceDC, check);
 }
 
-NormalProtocolConformance *GetImplicitSendableRequest::evaluate(
+ProtocolConformance *GetImplicitSendableRequest::evaluate(
     Evaluator &evaluator, NominalTypeDecl *nominal) const {
   // Protocols never get implicit Sendable conformances.
   if (isa<ProtocolDecl>(nominal))
@@ -3900,14 +3900,14 @@ NormalProtocolConformance *GetImplicitSendableRequest::evaluate(
     return nullptr;
   }
 
+  ASTContext &ctx = nominal->getASTContext();
+  auto proto = ctx.getProtocol(KnownProtocolKind::Sendable);
+  if (!proto)
+    return nullptr;
+
   // Local function to form the implicit conformance.
   auto formConformance = [&](const DeclAttribute *attrMakingUnavailable)
         -> NormalProtocolConformance * {
-    ASTContext &ctx = nominal->getASTContext();
-    auto proto = ctx.getProtocol(KnownProtocolKind::Sendable);
-    if (!proto)
-      return nullptr;
-
     DeclContext *conformanceDC = nominal;
     if (attrMakingUnavailable) {
       llvm::VersionTuple NoVersion;
@@ -3959,17 +3959,22 @@ NormalProtocolConformance *GetImplicitSendableRequest::evaluate(
 
   // A non-protocol type with a global actor is implicitly Sendable.
   if (nominal->getGlobalActorAttr()) {
-    // If this is a class, check the superclass. We won't infer Sendable
-    // if the superclass is already Sendable, to avoid introducing redundant
-    // conformances.
+    // If this is a class, check the superclass. If it's already Sendable,
+    // form an inherited conformance.
     if (classDecl) {
       if (Type superclass = classDecl->getSuperclass()) {
         auto classModule = classDecl->getParentModule();
-        if (TypeChecker::conformsToKnownProtocol(
+        if (auto inheritedConformance = TypeChecker::conformsToProtocol(
                 classDecl->mapTypeIntoContext(superclass),
-                KnownProtocolKind::Sendable,
-                classModule, /*allowMissing=*/false))
-          return nullptr;
+                proto, classModule, /*allowMissing=*/false)) {
+          inheritedConformance = inheritedConformance
+              .mapConformanceOutOfContext();
+          if (inheritedConformance.isConcrete()) {
+            return ctx.getInheritedConformance(
+                nominal->getDeclaredInterfaceType(),
+                inheritedConformance.getConcrete());
+          }
+        }
       }
     }
 

test/ClangImporter/objc_async.swift

@@ -218,4 +218,14 @@ func testMirrored(instance: ClassWithAsync) async {
   }
 }
 
+@MainActor class MyView: NXView {
+  func f() {
+    Task {
+      await self.g()
+    }
+  }
+
+  func g() async { }
+}
+
 } // SwiftStdlib 5.5