Operator methods are not @objc-compatible. (#4562)

https://bugs.swift.org/browse/SR-2419
(cherry picked from commit 4372a30)

Author: jrose-apple

include/swift/AST/DiagnosticsSema.def

@@ -2728,6 +2728,10 @@ ERROR(objc_in_extension_context,none,
       "members of constrained extensions cannot be declared @objc", ())
 ERROR(objc_in_generic_extension,none,
       "@objc is not supported within extensions of generic classes", ())
+ERROR(objc_operator, none,
+      "operator methods cannot be declared @objc", ())
+ERROR(objc_operator_proto, none,
+      "@objc protocols may not have operator requirements", ())
 
 ERROR(objc_for_generic_class,none,
       "generic subclasses of '@objc' classes cannot have an explicit '@objc' "

lib/Sema/TypeCheckDecl.cpp

@@ -2062,6 +2062,8 @@ static Optional<ObjCReason> shouldMarkAsObjC(TypeChecker &TC,
     return ObjCReason::WitnessToObjC;
   else if (VD->isInvalid())
     return None;
+  else if (VD->isOperator())
+    return None;
   // Implicitly generated declarations are not @objc, except for constructors.
   else if (!allowImplicit && VD->isImplicit())
     return None;
@@ -8119,12 +8121,11 @@ static void validateAttributes(TypeChecker &TC, Decl *D) {
         error = diag::objc_enum_case_req_objc_enum;
       else if (objcAttr->hasName() && EED->getParentCase()->getElements().size() > 1)
         error = diag::objc_enum_case_multi;
-    } else if (isa<FuncDecl>(D)) {
-      auto func = cast<FuncDecl>(D);
+    } else if (auto *func = dyn_cast<FuncDecl>(D)) {
       if (!checkObjCDeclContext(D))
         error = diag::invalid_objc_decl_context;
       else if (func->isOperator())
-        error = diag::invalid_objc_decl;
+        error = diag::objc_operator;
       else if (func->isAccessor() && !func->isGetterOrSetter())
         error = diag::objc_observing_accessor;
     } else if (isa<ConstructorDecl>(D) ||

lib/Sema/TypeCheckType.cpp

@@ -2942,6 +2942,13 @@ bool TypeChecker::isRepresentableInObjC(
   if (checkObjCInExtensionContext(*this, AFD, Diagnose))
     return false;
 
+  if (AFD->isOperator()) {
+    assert(isa<ProtocolDecl>(AFD->getDeclContext()) &&
+           "all other cases should be caught earlier");
+    diagnose(AFD, diag::objc_operator_proto);
+    return false;
+  }
+
   if (auto *FD = dyn_cast<FuncDecl>(AFD)) {
     if (FD->isAccessor()) {
       // Accessors can only be @objc if the storage declaration is.

test/attr/attr_objc.swift

@@ -2068,3 +2068,19 @@ class ConformsToProtocolThrowsObjCName2 : ProtocolThrowsObjCName {
 func ==(lhs: ObjC_Class1, rhs: ObjC_Class1) -> Bool {
   return true
 }
+
+// CHECK-LABEL: @objc class OperatorInClass
+@objc class OperatorInClass {
+  // CHECK: {{^}} static func ==(lhs: OperatorInClass, rhs: OperatorInClass) -> Bool
+  static func ==(lhs: OperatorInClass, rhs: OperatorInClass) -> Bool {
+    return true
+  }
+  // CHECK: {{^}} @objc static func +(lhs: OperatorInClass, rhs: OperatorInClass) -> OperatorInClass
+  @objc static func +(lhs: OperatorInClass, rhs: OperatorInClass) -> OperatorInClass { // expected-error {{operator methods cannot be declared @objc}}
+    return lhs
+  }
+} // CHECK: {{^}$}}
+
+@objc protocol OperatorInProtocol {
+  static func +(lhs: Self, rhs: Self) -> Self // expected-error {{@objc protocols may not have operator requirements}}
+}