Sema: Update 'can be represented in @objc' logic for subclass existentials

Author: slavapestov

include/swift/AST/DiagnosticsSema.def

@@ -3093,7 +3093,11 @@ ERROR(function_type_no_parens,none,
 NOTE(not_objc_empty_protocol_composition,none,
      "'Any' is not considered '@objc'; use 'AnyObject' instead", ())
 NOTE(not_objc_protocol,none,
-     "protocol %0 is not '@objc'", (Type))
+     "protocol-constrained type containing protocol %0 cannot be represented "
+     "in Objective-C", (Type))
+NOTE(not_objc_class_constraint,none,
+     "protocol-constrained type containing class %0 cannot be represented "
+     "in Objective-C", (Type))
 NOTE(not_objc_error_protocol_composition,none,
      "protocol-constrained type containing 'Error' cannot be represented "
      "in Objective-C", ())

lib/AST/Type.cpp

@@ -2006,10 +2006,18 @@ getObjCObjectRepresentable(Type type, const DeclContext *dc) {
       return ForeignRepresentableKind::Object;
   }
 
-  // Objective-C existential types.
-  if (type->isObjCExistentialType())
-    return ForeignRepresentableKind::Object;
-  
+  // Objective-C existential types are trivially representable if
+  // they don't have a superclass constraint, or if the superclass
+  // constraint is an @objc class.
+  if (type->isExistentialType()) {
+    auto layout = type->getExistentialLayout();
+    if (layout.isObjC() &&
+        (!layout.superclass ||
+         getObjCObjectRepresentable(layout.superclass, dc) ==
+           ForeignRepresentableKind::Object))
+      return ForeignRepresentableKind::Object;
+  }
+
   // Any can be bridged to id.
   if (type->isAny()) {
     return ForeignRepresentableKind::Bridged;

lib/Sema/TypeCheckType.cpp

@@ -3810,16 +3810,27 @@ void TypeChecker::diagnoseTypeNotRepresentableInObjC(const DeclContext *DC,
 
   // Special diagnostic for protocols and protocol compositions.
   if (T->isExistentialType()) {
-    SmallVector<ProtocolDecl *, 4> Protocols;
-    T->getExistentialTypeProtocols(Protocols);
-    if (Protocols.empty()) {
+    if (T->isAny()) {
       // Any is not @objc.
       diagnose(TypeRange.Start, diag::not_objc_empty_protocol_composition);
       return;
     }
+
+    auto layout = T->getExistentialLayout();
+
+    // See if the superclass is not @objc.
+    if (layout.superclass &&
+        !layout.superclass->getClassOrBoundGenericClass()->isObjC()) {
+      diagnose(TypeRange.Start, diag::not_objc_class_constraint,
+               layout.superclass);
+      return;
+    }
+
     // Find a protocol that is not @objc.
     bool sawErrorProtocol = false;
-    for (auto PD : Protocols) {
+    for (auto P : layout.getProtocols()) {
+      auto *PD = P->getDecl();
+
       if (PD->isSpecificProtocol(KnownProtocolKind::Error)) {
         sawErrorProtocol = true;
         break;

test/attr/attr_ibaction.swift

@@ -71,10 +71,10 @@ protocol CP2 : class { }
   // Protocol types
   @IBAction func action7(_: P1) {} // expected-error{{argument to @IBAction method cannot have non-object type 'P1'}}
   // expected-error@-1{{method cannot be marked @IBAction because the type of the parameter cannot be represented in Objective-C}}
-  // expected-note@-2{{protocol 'P1' is not '@objc'}}
+  // expected-note@-2{{protocol-constrained type containing protocol 'P1' cannot be represented in Objective-C}}
   @IBAction func action8(_: CP1) {} // expected-error{{argument to @IBAction method cannot have non-object type 'CP1'}}
   // expected-error@-1{{method cannot be marked @IBAction because the type of the parameter cannot be represented in Objective-C}}
-  // expected-note@-2{{protocol 'CP1' is not '@objc'}}
+  // expected-note@-2{{protocol-constrained type containing protocol 'CP1' cannot be represented in Objective-C}}
   @IBAction func action9(_: OP1) {}
   @IBAction func action10(_: P1?) {} // expected-error{{argument to @IBAction method cannot have non-object type}}
   // expected-error@-1{{method cannot be marked @IBAction because the type of the parameter cannot be represented in Objective-C}}

test/attr/attr_objc.swift

@@ -528,21 +528,21 @@ class subject_subscriptInvalid5 {
 class subject_subscriptInvalid6 {
   @objc
   subscript(a: PlainProtocol) -> Int { // expected-error {{subscript cannot be marked @objc because its type cannot be represented in Objective-C}}
-    // expected-note@-1{{protocol 'PlainProtocol' is not '@objc'}}
+    // expected-note@-1{{protocol-constrained type containing protocol 'PlainProtocol' cannot be represented in Objective-C}}
     get { return 0 }
   }
 }
 class subject_subscriptInvalid7 {
   @objc
   subscript(a: Protocol_Class1) -> Int { // expected-error {{subscript cannot be marked @objc because its type cannot be represented in Objective-C}}
-    // expected-note@-1{{protocol 'Protocol_Class1' is not '@objc'}}
+    // expected-note@-1{{protocol-constrained type containing protocol 'Protocol_Class1' cannot be represented in Objective-C}}
     get { return 0 }
   }
 }
 class subject_subscriptInvalid8 {
   @objc
   subscript(a: Protocol_Class1 & Protocol_Class2) -> Int { // expected-error {{subscript cannot be marked @objc because its type cannot be represented in Objective-C}}
-    // expected-note@-1{{protocol 'Protocol_Class1' is not '@objc'}}
+    // expected-note@-1{{protocol-constrained type containing protocol 'Protocol_Class1' cannot be represented in Objective-C}}
     get { return 0 }
   }
 }
@@ -641,7 +641,7 @@ class infer_instanceFunc1 {
 
   @objc func func12_(a: PlainProtocol) {}
   // expected-error@-1 {{method cannot be marked @objc because the type of the parameter cannot be represented in Objective-C}}
-  // expected-note@-2 {{protocol 'PlainProtocol' is not '@objc'}}
+  // expected-note@-2 {{protocol-constrained type containing protocol 'PlainProtocol' cannot be represented in Objective-C}}
 
   func func13(a: Class_ObjC1) {}
 // CHECK-LABEL: @objc func func13(a: Class_ObjC1) {
@@ -653,7 +653,7 @@ class infer_instanceFunc1 {
 
   @objc func func14_(a: Protocol_Class1) {}
   // expected-error@-1 {{method cannot be marked @objc because the type of the parameter cannot be represented in Objective-C}}
-  // expected-note@-2 {{protocol 'Protocol_Class1' is not '@objc'}}
+  // expected-note@-2 {{protocol-constrained type containing protocol 'Protocol_Class1' cannot be represented in Objective-C}}
 
   func func15(a: Protocol_ObjC1) {}
 // CHECK-LABEL: @objc func func15(a: Protocol_ObjC1) {
@@ -802,7 +802,7 @@ class infer_instanceVar1 {
 
   @objc var (instanceVar1_, instanceVar2_): (Int, PlainProtocol)
   // expected-error@-1 {{property cannot be marked @objc because its type cannot be represented in Objective-C}}
-  // expected-note@-2 {{protocol 'PlainProtocol' is not '@objc'}}
+  // expected-note@-2 {{protocol-constrained type containing protocol 'PlainProtocol' cannot be represented in Objective-C}}
 
   var intstanceVar4: Int {
   // CHECK: @objc var intstanceVar4: Int {
@@ -940,7 +940,7 @@ class infer_instanceVar1 {
 
   @objc var var_PlainProtocol_: PlainProtocol
   // expected-error@-1 {{property cannot be marked @objc because its type cannot be represented in Objective-C}}
-  // expected-note@-2 {{protocol 'PlainProtocol' is not '@objc'}}
+  // expected-note@-2 {{protocol-constrained type containing protocol 'PlainProtocol' cannot be represented in Objective-C}}
 
   var var_ClassObjC: Class_ObjC1
 // CHECK-LABEL: @objc var var_ClassObjC: Class_ObjC1
@@ -952,7 +952,7 @@ class infer_instanceVar1 {
 
   @objc var var_ProtocolClass_: Protocol_Class1
   // expected-error@-1 {{property cannot be marked @objc because its type cannot be represented in Objective-C}}
-  // expected-note@-2 {{protocol 'Protocol_Class1' is not '@objc'}}
+  // expected-note@-2 {{protocol-constrained type containing protocol 'Protocol_Class1' cannot be represented in Objective-C}}
 
   var var_ProtocolObjC: Protocol_ObjC1
 // CHECK-LABEL: @objc var var_ProtocolObjC: Protocol_ObjC1
@@ -1020,49 +1020,49 @@ class infer_instanceVar1 {
 
   @objc var var_Existential1_: PlainProtocol
   // expected-error@-1 {{property cannot be marked @objc because its type cannot be represented in Objective-C}}
-  // expected-note@-2 {{protocol 'PlainProtocol' is not '@objc'}}
+  // expected-note@-2 {{protocol-constrained type containing protocol 'PlainProtocol' cannot be represented in Objective-C}}
 
   var var_Existential2: PlainProtocol & PlainProtocol
 // CHECK-LABEL: {{^}}  var var_Existential2: PlainProtocol
 
   @objc var var_Existential2_: PlainProtocol & PlainProtocol
   // expected-error@-1 {{property cannot be marked @objc because its type cannot be represented in Objective-C}}
-  // expected-note@-2 {{protocol 'PlainProtocol' is not '@objc'}}
+  // expected-note@-2 {{protocol-constrained type containing protocol 'PlainProtocol' cannot be represented in Objective-C}}
 
   var var_Existential3: PlainProtocol & Protocol_Class1
 // CHECK-LABEL: {{^}}  var var_Existential3: PlainProtocol & Protocol_Class1
 
   @objc var var_Existential3_: PlainProtocol & Protocol_Class1
   // expected-error@-1 {{property cannot be marked @objc because its type cannot be represented in Objective-C}}
-  // expected-note@-2 {{protocol 'PlainProtocol' is not '@objc'}}
+  // expected-note@-2 {{protocol-constrained type containing protocol 'PlainProtocol' cannot be represented in Objective-C}}
 
   var var_Existential4: PlainProtocol & Protocol_ObjC1
 // CHECK-LABEL: {{^}}  var var_Existential4: PlainProtocol & Protocol_ObjC1
 
   @objc var var_Existential4_: PlainProtocol & Protocol_ObjC1
   // expected-error@-1 {{property cannot be marked @objc because its type cannot be represented in Objective-C}}
-  // expected-note@-2 {{protocol 'PlainProtocol' is not '@objc'}}
+  // expected-note@-2 {{protocol-constrained type containing protocol 'PlainProtocol' cannot be represented in Objective-C}}
 
   var var_Existential5: Protocol_Class1
   // CHECK-LABEL: {{^}}  var var_Existential5: Protocol_Class1
 
   @objc var var_Existential5_: Protocol_Class1
   // expected-error@-1 {{property cannot be marked @objc because its type cannot be represented in Objective-C}}
-  // expected-note@-2 {{protocol 'Protocol_Class1' is not '@objc'}}
+  // expected-note@-2 {{protocol-constrained type containing protocol 'Protocol_Class1' cannot be represented in Objective-C}}
 
   var var_Existential6: Protocol_Class1 & Protocol_Class2
 // CHECK-LABEL: {{^}}  var var_Existential6: Protocol_Class1 & Protocol_Class2
 
   @objc var var_Existential6_: Protocol_Class1 & Protocol_Class2
   // expected-error@-1 {{property cannot be marked @objc because its type cannot be represented in Objective-C}}
-  // expected-note@-2 {{protocol 'Protocol_Class1' is not '@objc'}}
+  // expected-note@-2 {{protocol-constrained type containing protocol 'Protocol_Class1' cannot be represented in Objective-C}}
 
   var var_Existential7: Protocol_Class1 & Protocol_ObjC1
 // CHECK-LABEL: {{^}}  var var_Existential7: Protocol_Class1 & Protocol_ObjC1
 
   @objc var var_Existential7_: Protocol_Class1 & Protocol_ObjC1
   // expected-error@-1 {{property cannot be marked @objc because its type cannot be represented in Objective-C}}
-  // expected-note@-2 {{protocol 'Protocol_Class1' is not '@objc'}}
+  // expected-note@-2 {{protocol-constrained type containing protocol 'Protocol_Class1' cannot be represented in Objective-C}}
 
   var var_Existential8: Protocol_ObjC1
 // CHECK-LABEL: @objc var var_Existential8: Protocol_ObjC1

test/type/subclass_composition_objc.swift

@@ -0,0 +1,23 @@
+// RUN: %target-typecheck-verify-swift -enable-experimental-subclass-existentials -disable-objc-attr-requires-foundation-module
+
+@objc class ObjCClass {}
+@objc protocol ObjCProtocol {}
+
+class SwiftClass {}
+protocol SwiftProtocol {}
+
+class SomeMethods {
+
+  @objc
+  func canRepresentInObjC(x: ObjCClass & ObjCProtocol) {}
+
+  @objc
+  func cannotRepresentInObjC(x: SwiftClass & ObjCProtocol) {}
+  // expected-error@-1 {{method cannot be marked @objc because the type of the parameter cannot be represented in Objective-C}}
+  // expected-note@-2 {{protocol-constrained type containing class 'SwiftClass' cannot be represented in Objective-C}}
+
+  @objc
+  func alsoCannotRepresentInObjC(x: ObjCClass & SwiftProtocol) {}
+  // expected-error@-1 {{method cannot be marked @objc because the type of the parameter cannot be represented in Objective-C}}
+  // expected-note@-2 {{protocol-constrained type containing protocol 'SwiftProtocol' cannot be represented in Objective-C}}
+}