Merge pull request #69827 from xedin/fix-invalid-sendable-handling-in-existential-types

[Sema] Don't propagate `allowsMissing` to existential superclass check

Author: xedin

lib/Sema/TypeCheckProtocol.cpp

@@ -5777,12 +5777,16 @@ TypeChecker::containsProtocol(Type T, ProtocolDecl *Proto, ModuleDecl *M,
 
     // First, if we have a superclass constraint, the class may conform
     // concretely.
+    //
+    // Note that `allowMissing` is not propagated here because it
+    // would result in a missing conformance if type is `& Sendable`
+    // protocol composition. It's handled for type as a whole below.
     if (auto superclass = layout.getSuperclass()) {
       auto result =
           (skipConditionalRequirements
-           ? M->lookupConformance(superclass, Proto, allowMissing)
-           : TypeChecker::conformsToProtocol(
-               superclass, Proto, M, allowMissing));
+               ? M->lookupConformance(superclass, Proto, /*allowMissing=*/false)
+               : TypeChecker::conformsToProtocol(superclass, Proto, M,
+                                                 /*allowMissing=*/false));
       if (result) {
         return result;
       }
@@ -5800,15 +5804,8 @@ TypeChecker::containsProtocol(Type T, ProtocolDecl *Proto, ModuleDecl *M,
         return ProtocolConformanceRef(Proto);
     }
 
-    // FIXME: Unify with shouldCreateMissingConformances
-    if (allowMissing &&
-        Proto->isSpecificProtocol(KnownProtocolKind::Sendable)) {
-      return ProtocolConformanceRef(
-          M->getASTContext().getBuiltinConformance(
-            T, Proto, BuiltinConformanceKind::Missing));
-    }
-
-    return ProtocolConformanceRef::forInvalid();
+    return allowMissing ? ProtocolConformanceRef::forMissingOrInvalid(T, Proto)
+                        : ProtocolConformanceRef::forInvalid();
   }
 
   // For non-existential types, this is equivalent to checking conformance.

test/ClangImporter/objc_async.swift

@@ -369,9 +369,7 @@ func testSender(
   sender.sendAnyArray([nonSendableObject])
   // expected-warning@-1 {{conformance of 'NonSendableClass' to 'Sendable' is unavailable; this is an error in Swift 6}}
 
-  sender.sendGeneric(sendableGeneric)
-  // expected-warning@-1{{type 'GenericObject<SendableClass>' does not conform to the 'Sendable' protocol}}
-  // FIXME: Shouldn't warn
+  sender.sendGeneric(sendableGeneric) // no warning
 
   sender.sendGeneric(nonSendableGeneric)
   // expected-warning@-1 {{type 'GenericObject<SendableClass>' does not conform to the 'Sendable' protocol}}

test/Concurrency/sendable_existentials.swift

@@ -56,3 +56,14 @@ func testESilently(a: Any, aOpt: Any?) {
   _ = sendable
   _ = arrayOfSendable
 }
+
+func testErasure() {
+  class A {}
+  class B : A {}
+
+  func produce() -> any B & Sendable {
+    fatalError()
+  }
+
+  let _: any A & Sendable = produce() // no warning
+}