Add 'operator' keyword

compiler/backend/src/org/jetbrains/kotlin/codegen/AccessorForConstructorDescriptor.kt

@@ -47,7 +47,8 @@ public class AccessorForConstructorDescriptor(
                 copyValueParameters(calleeDescriptor),
                 calleeDescriptor.returnType,
                 Modality.FINAL,
-                Visibilities.INTERNAL
+                Visibilities.INTERNAL,
+                false
         )
     }
 }

compiler/backend/src/org/jetbrains/kotlin/codegen/AccessorForFunctionDescriptor.java

@@ -47,7 +47,8 @@ public class AccessorForFunctionDescriptor extends AbstractAccessorForFunctionDe
                    copyValueParameters(descriptor),
                    descriptor.getReturnType(),
                    Modality.FINAL,
-                   Visibilities.INTERNAL);
+                   Visibilities.INTERNAL,
+                   descriptor.isOperator());
     }
 
     @NotNull

compiler/backend/src/org/jetbrains/kotlin/codegen/ClosureCodegen.java

@@ -197,8 +197,8 @@ public class ClosureCodegen extends MemberCodegen<JetElement> {
 
             descriptorForBridges
                     .initialize(null, erasedInterfaceFunction.getDispatchReceiverParameter(), erasedInterfaceFunction.getTypeParameters(),
-                                erasedInterfaceFunction.getValueParameters(), erasedInterfaceFunction.getReturnType(), Modality.OPEN,
+                                erasedInterfaceFunction.getValueParameters(), erasedInterfaceFunction.getReturnType(),
-                                erasedInterfaceFunction.getVisibility());
+                                Modality.OPEN, erasedInterfaceFunction.getVisibility(), false);
 
             descriptorForBridges.addOverriddenDescriptor(erasedInterfaceFunction);
             functionCodegen.generateBridges(descriptorForBridges);

compiler/backend/src/org/jetbrains/kotlin/codegen/MemberCodegen.java

@@ -337,7 +337,7 @@ public abstract class MemberCodegen<T extends JetElement/* TODO: & JetDeclaratio
             clInit.initialize(null, null, Collections.<TypeParameterDescriptor>emptyList(),
                               Collections.<ValueParameterDescriptor>emptyList(),
                               DescriptorUtilPackage.getModule(descriptor).getBuiltIns().getUnitType(),
-                              null, Visibilities.PRIVATE);
+                              null, Visibilities.PRIVATE, false);
 
             this.clInit = new ExpressionCodegen(mv, new FrameMap(), Type.VOID_TYPE, context.intoFunction(clInit), state, this);
         }

compiler/backend/src/org/jetbrains/kotlin/codegen/PropertyReferenceCodegen.kt

@@ -150,7 +150,7 @@ public class PropertyReferenceCodegen(
                         SourceElement.NO_SOURCE
                 )
                 fakeDescriptor.initialize(null, classDescriptor.getThisAsReceiverParameter(), emptyList(), emptyList(),
-                                          classDescriptor.builtIns.getAnyType(), Modality.OPEN, Visibilities.PUBLIC)
+                                          classDescriptor.builtIns.getAnyType(), Modality.OPEN, Visibilities.PUBLIC, false)
 
                 val fakeCodegen = ExpressionCodegen(
                         this, FrameMap(), OBJECT_TYPE, context.intoFunction(fakeDescriptor), state, this@PropertyReferenceCodegen

compiler/backend/src/org/jetbrains/kotlin/codegen/SamWrapperCodegen.java

@@ -162,8 +162,8 @@ public class SamWrapperCodegen {
 
         descriptorForBridges
                 .initialize(null, originalInterfaceErased.getDispatchReceiverParameter(), originalInterfaceErased.getTypeParameters(),
-                            originalInterfaceErased.getValueParameters(), originalInterfaceErased.getReturnType(), Modality.OPEN,
+                            originalInterfaceErased.getValueParameters(), originalInterfaceErased.getReturnType(),
-                            originalInterfaceErased.getVisibility());
+                            Modality.OPEN, originalInterfaceErased.getVisibility(), false);
 
         descriptorForBridges.addOverriddenDescriptor(originalInterfaceErased);
         codegen.generateBridges(descriptorForBridges);

compiler/frontend.java/src/org/jetbrains/kotlin/load/java/sam/SingleAbstractMethodUtils.java

@@ -170,7 +170,8 @@ public class SingleAbstractMethodUtils {
                 Arrays.asList(parameter),
                 returnType,
                 Modality.FINAL,
-                samInterface.getVisibility()
+                samInterface.getVisibility(),
+                false
         );
 
         return result;
@@ -206,7 +207,8 @@ public class SingleAbstractMethodUtils {
                         valueParameters,
                         returnType,
                         Modality.FINAL,
-                        original.getVisibility()
+                        original.getVisibility(),
+                        false
                 );
             }
         });

compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/kotlinSignature/SignaturesPropagationData.java

@@ -116,7 +116,8 @@ public class SignaturesPropagationData {
                 autoValueParameters,
                 autoReturnType,
                 Modality.OPEN,
-                Visibilities.PUBLIC
+                Visibilities.PUBLIC,
+                false
         );
         return autoMethodDescriptor;
     }

compiler/frontend.java/src/org/jetbrains/kotlin/synthetic/SamAdapterFunctionsScope.kt

@@ -128,7 +128,7 @@ class SamAdapterFunctionsScope(storageManager: StorageManager) : JetScope by Jet
 
                 val visibility = syntheticExtensionVisibility(sourceFunction)
 
-                descriptor.initialize(receiverType, null, typeParameters, valueParameters, returnType, Modality.FINAL, visibility)
+                descriptor.initialize(receiverType, null, typeParameters, valueParameters, returnType, Modality.FINAL, visibility, false)
 
                 return descriptor
             }
@@ -148,6 +148,7 @@ class SamAdapterFunctionsScope(storageManager: StorageManager) : JetScope by Jet
                 newOwner: DeclarationDescriptor,
                 newModality: Modality,
                 newVisibility: Visibility,
+                newIsOperator: Boolean,
                 original: FunctionDescriptor?,
                 copyOverrides: Boolean,
                 kind: CallableMemberDescriptor.Kind,
@@ -156,7 +157,7 @@ class SamAdapterFunctionsScope(storageManager: StorageManager) : JetScope by Jet
                 newReturnType: JetType
         ): FunctionDescriptor? {
             val descriptor = super<SimpleFunctionDescriptorImpl>.doSubstitute(
-                    originalSubstitutor, newOwner, newModality, newVisibility, original,
+                    originalSubstitutor, newOwner, newModality, newVisibility, newIsOperator, original,
                     copyOverrides, kind, newValueParameterDescriptors, newExtensionReceiverParameterType, newReturnType)
                 as MyFunctionDescriptor? ?: return null
 

compiler/frontend/src/org/jetbrains/kotlin/lexer/JetTokens.java

@@ -176,6 +176,7 @@ public interface JetTokens {
     JetModifierKeywordToken EXTERNAL_KEYWORD    = JetModifierKeywordToken.softKeywordModifier("external");
     JetModifierKeywordToken ANNOTATION_KEYWORD    = JetModifierKeywordToken.softKeywordModifier("annotation");
     JetModifierKeywordToken CROSSINLINE_KEYWORD    = JetModifierKeywordToken.softKeywordModifier("crossinline");
+    JetModifierKeywordToken OPERATOR_KEYWORD = JetModifierKeywordToken.softKeywordModifier("operator");
 
     JetModifierKeywordToken CONST_KEYWORD = JetModifierKeywordToken.softKeywordModifier("const");
 
@@ -196,7 +197,7 @@ public interface JetTokens {
                                              FIELD_KEYWORD, PROPERTY_KEYWORD, RECEIVER_KEYWORD, PARAM_KEYWORD, SPARAM_KEYWORD,
                                              LATE_INIT_KEYWORD,
                                              DATA_KEYWORD, INLINE_KEYWORD, NOINLINE_KEYWORD, TAILREC_KEYWORD, EXTERNAL_KEYWORD,
-                                             ANNOTATION_KEYWORD, CROSSINLINE_KEYWORD, CONST_KEYWORD
+                                             ANNOTATION_KEYWORD, CROSSINLINE_KEYWORD, CONST_KEYWORD, OPERATOR_KEYWORD
     );
 
     /*
@@ -210,7 +211,7 @@ public interface JetTokens {
                     PUBLIC_KEYWORD, INTERNAL_KEYWORD, PROTECTED_KEYWORD, OUT_KEYWORD, IN_KEYWORD, FINAL_KEYWORD, VARARG_KEYWORD,
                     REIFIED_KEYWORD, COMPANION_KEYWORD, SEALED_KEYWORD, LATE_INIT_KEYWORD,
                     DATA_KEYWORD, INLINE_KEYWORD, NOINLINE_KEYWORD, TAILREC_KEYWORD, EXTERNAL_KEYWORD, ANNOTATION_KEYWORD, CROSSINLINE_KEYWORD,
-                    CONST_KEYWORD
+                    CONST_KEYWORD, OPERATOR_KEYWORD
             };
 
     // Please synchronize this array with org.jetbrains.kotlin.descriptors.annotations.ANNOTATION_MODIFIERS_FQ_NAMES

compiler/frontend/src/org/jetbrains/kotlin/psi/stubs/elements/JetFileElementType.java

@@ -34,7 +34,7 @@ import org.jetbrains.kotlin.psi.stubs.KotlinFileStub;
 import java.io.IOException;
 
 public class JetFileElementType extends IStubFileElementType<KotlinFileStub> {
-    public static final int STUB_VERSION = 58;
+    public static final int STUB_VERSION = 59;
 
     private static final String NAME = "kotlin.FILE";
 

compiler/frontend/src/org/jetbrains/kotlin/resolve/DescriptorResolver.java

@@ -241,7 +241,8 @@ public class DescriptorResolver {
                 Collections.<ValueParameterDescriptor>emptyList(),
                 returnType,
                 Modality.FINAL,
-                property.getVisibility()
+                property.getVisibility(),
+                false
         );
 
         trace.record(BindingContext.DATA_CLASS_COMPONENT_FUNCTION, parameter, functionDescriptor);
@@ -289,7 +290,8 @@ public class DescriptorResolver {
                 parameterDescriptors,
                 returnType,
                 Modality.FINAL,
-                Visibilities.PUBLIC
+                Visibilities.PUBLIC,
+                false
         );
 
         trace.record(BindingContext.DATA_CLASS_COPY_FUNCTION, classDescriptor, functionDescriptor);

compiler/frontend/src/org/jetbrains/kotlin/resolve/FunctionDescriptorResolver.kt

@@ -26,6 +26,7 @@ import org.jetbrains.kotlin.descriptors.impl.SimpleFunctionDescriptorImpl.create
 import org.jetbrains.kotlin.descriptors.impl.ValueParameterDescriptorImpl
 import org.jetbrains.kotlin.diagnostics.DiagnosticUtils
 import org.jetbrains.kotlin.diagnostics.Errors.*
+import org.jetbrains.kotlin.lexer.JetTokens
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.resolve.DescriptorResolver.*
@@ -170,7 +171,8 @@ class FunctionDescriptorResolver(
                 valueParameterDescriptors,
                 returnType,
                 modality,
-                visibility
+                visibility,
+                function.hasModifier(JetTokens.OPERATOR_KEYWORD)
         )
         receiverType?.let { ForceResolveUtil.forceResolveAllContents(it.getAnnotations()) }
         for (valueParameterDescriptor in valueParameterDescriptors) {

compiler/frontend/src/org/jetbrains/kotlin/resolve/FunctionDescriptorUtil.java

@@ -103,7 +103,8 @@ public class FunctionDescriptorUtil {
                                       KotlinBuiltIns.getValueParameters(functionDescriptor, functionType),
                                       KotlinBuiltIns.getReturnTypeFromFunctionType(functionType),
                                       modality,
-                                      visibility);
+                                      visibility,
+                                      false);
     }
 
     public static <D extends CallableDescriptor> D alphaConvertTypeParameters(D candidate) {
@@ -155,7 +156,8 @@ public class FunctionDescriptorUtil {
                 parameters,
                 function.getReturnType(),
                 function.getModality(),
-                function.getVisibility());
+                function.getVisibility(),
+                function.isOperator());
         return descriptor;
     }
 }

compiler/frontend/src/org/jetbrains/kotlin/resolve/ModifiersChecker.kt

@@ -66,7 +66,8 @@ public object ModifierCheckerCore {
             EXTERNAL_KEYWORD  to EnumSet.of(FUNCTION, PROPERTY_GETTER, PROPERTY_SETTER),
             ANNOTATION_KEYWORD to EnumSet.of(ANNOTATION_CLASS),
             CROSSINLINE_KEYWORD to EnumSet.of(VALUE_PARAMETER),
-            CONST_KEYWORD     to EnumSet.of(MEMBER_PROPERTY, TOP_LEVEL_PROPERTY)
+            CONST_KEYWORD     to EnumSet.of(MEMBER_PROPERTY, TOP_LEVEL_PROPERTY),
+            OPERATOR_KEYWORD  to EnumSet.of(FUNCTION)
     )
 
     // NOTE: redundant targets must be possible!

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tasks/dynamicCalls.kt

@@ -129,7 +129,8 @@ object DynamicCallableDescriptors {
                 createValueParameters(functionDescriptor, call),
                 DynamicType,
                 Modality.FINAL,
-                Visibilities.PUBLIC
+                Visibilities.PUBLIC,
+                false
         )
         return functionDescriptor
     }

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tasks/synthesizedInvokes.kt

@@ -80,7 +80,8 @@ private fun createSynthesizedFunctionWithFirstParameterAsReceiver(descriptor: Fu
             },
             original.getReturnType(),
             original.getModality(),
-            original.getVisibility()
+            original.getVisibility(),
+            original.isOperator
     )
 
     return result

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/ControlStructureTypingUtils.java

@@ -124,7 +124,8 @@ public class ControlStructureTypingUtils {
                 valueParameters,
                 type,
                 Modality.FINAL,
-                Visibilities.PUBLIC
+                Visibilities.PUBLIC,
+                false
         );
         return function;
     }

compiler/serialization/src/org/jetbrains/kotlin/serialization/DescriptorSerializer.java

@@ -180,6 +180,11 @@ public class DescriptorSerializer {
         boolean hasConstant = false;
         boolean lateInit = false;
         boolean isConst = false;
+        boolean isOperator = false;
+
+        if (descriptor instanceof FunctionDescriptor) {
+            isOperator = ((FunctionDescriptor) descriptor).isOperator();
+        }
 
         if (descriptor instanceof PropertyDescriptor) {
             PropertyDescriptor propertyDescriptor = (PropertyDescriptor) descriptor;
@@ -235,7 +240,8 @@ public class DescriptorSerializer {
                 hasSetter,
                 hasConstant,
                 lateInit,
-                isConst
+                isConst,
+                isOperator
         ));
 
         for (TypeParameterDescriptor typeParameterDescriptor : descriptor.getTypeParameters()) {

compiler/testData/loadJava/compiledKotlin/fun/OperatorKeyword.kt

@@ -0,0 +1,5 @@
+package test
+
+class Example {
+    operator fun plus(other: Example) {}
+}

compiler/testData/loadJava/compiledKotlin/fun/OperatorKeyword.txt

@@ -0,0 +1,6 @@
+package test
+
+public final class Example {
+    /*primary*/ public constructor Example()
+    public final operator fun plus(/*0*/ other: test.Example): kotlin.Unit
+}

compiler/testData/resolvedCalls/functionTypes/invokeForExtensionFunctionType.txt

@@ -5,7 +5,7 @@ fun bar(f: Int.()->Unit) {
 
 Resolved call:
 
-Resulting descriptor: fun Int.invoke(): Unit defined in kotlin.Function1
+Resulting descriptor: operator fun Int.invoke(): Unit defined in kotlin.Function1
 
 Explicit receiver kind = BOTH_RECEIVERS
 Dispatch receiver = f {[@kotlin.Extension] Function1<Int, Unit>}

compiler/testData/resolvedCalls/functionTypes/invokeForFunctionType.txt

@@ -5,7 +5,7 @@ fun bar(f: ()->Unit) {
 
 Resolved call:
 
-Resulting descriptor: fun invoke(): Unit defined in kotlin.Function0
+Resulting descriptor: operator fun invoke(): Unit defined in kotlin.Function0
 
 Explicit receiver kind = DISPATCH_RECEIVER
 Dispatch receiver = f {Function0<Unit>}

compiler/testData/resolvedCalls/functionTypes/valOfExtensionFunctionTypeInvoke.txt

@@ -9,7 +9,7 @@ interface A {
 
 Resolved call:
 
-Resulting descriptor: fun Int.invoke(): Unit defined in kotlin.Function1
+Resulting descriptor: operator fun Int.invoke(): Unit defined in kotlin.Function1
 
 Explicit receiver kind = BOTH_RECEIVERS
 Dispatch receiver = foo {[@kotlin.Extension] Function1<Int, Unit>}

compiler/testData/resolvedCalls/functionTypes/valOfFunctionTypeInvoke.txt

@@ -9,7 +9,7 @@ fun test(a: A) {
 
 Resolved call:
 
-Resulting descriptor: fun invoke(p1: Int): Int defined in kotlin.Function1
+Resulting descriptor: operator fun invoke(p1: Int): Int defined in kotlin.Function1
 
 Explicit receiver kind = DISPATCH_RECEIVER
 Dispatch receiver = foo {Function1<Int, Int>}

compiler/tests/org/jetbrains/kotlin/jvm/compiler/LoadJavaTestGenerated.java

@@ -4078,6 +4078,12 @@ public class LoadJavaTestGenerated extends AbstractLoadJavaTest {
                 doTestCompiledKotlin(fileName);
             }
 
+            @TestMetadata("OperatorKeyword.kt")
+            public void testOperatorKeyword() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/loadJava/compiledKotlin/fun/OperatorKeyword.kt");
+                doTestCompiledKotlin(fileName);
+            }
+
             @TestMetadata("PropagateDeepSubclass.kt")
             public void testPropagateDeepSubclass() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/loadJava/compiledKotlin/fun/PropagateDeepSubclass.kt");

compiler/tests/org/jetbrains/kotlin/jvm/runtime/JvmRuntimeDescriptorLoaderTestGenerated.java

@@ -2187,6 +2187,12 @@ public class JvmRuntimeDescriptorLoaderTestGenerated extends AbstractJvmRuntimeD
                 doTest(fileName);
             }
 
+            @TestMetadata("OperatorKeyword.kt")
+            public void testOperatorKeyword() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/loadJava/compiledKotlin/fun/OperatorKeyword.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("PropagateDeepSubclass.kt")
             public void testPropagateDeepSubclass() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/loadJava/compiledKotlin/fun/PropagateDeepSubclass.kt");

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/descriptors/JavaConstructorDescriptor.java

@@ -109,7 +109,8 @@ public class JavaConstructorDescriptor extends ConstructorDescriptorImpl impleme
                 DescriptorsPackage.createEnhancedValueParameters(enhancedValueParametersTypes, getValueParameters(), enhanced),
                 enhancedReturnType,
                 getModality(),
-                getVisibility()
+                getVisibility(),
+                false
         );
 
         return enhanced;

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/descriptors/JavaMethodDescriptor.java

@@ -122,7 +122,7 @@ public class JavaMethodDescriptor extends SimpleFunctionDescriptorImpl implement
         // 1. creates full copy of descriptor
         // 2. copies method's type parameters (with new containing declaration) and properly substitute to them in value parameters, return type and etc.
         JavaMethodDescriptor enhancedMethod = (JavaMethodDescriptor) doSubstitute(
-                TypeSubstitutor.EMPTY, getContainingDeclaration(), getModality(), getVisibility(), getOriginal(),
+                TypeSubstitutor.EMPTY, getContainingDeclaration(), getModality(), getVisibility(), false, getOriginal(),
                 /* copyOverrides = */ true, getKind(),
                 enhancedValueParameters, enhancedReceiverType, enhancedReturnType
         );

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/lazy/descriptors/LazyJavaScope.kt

@@ -126,7 +126,8 @@ public abstract class LazyJavaScope(
                 effectiveSignature.getValueParameters(),
                 effectiveSignature.getReturnType(),
                 Modality.convertFromFlags(method.isAbstract(), !method.isFinal()),
-                method.getVisibility()
+                method.getVisibility(),
+                false
         )
 
         functionDescriptorImpl.setParameterNamesStatus(effectiveSignature.hasStableParameterNames(), valueParameters.hasSynthesizedNames)

core/descriptors/src/org/jetbrains/kotlin/builtins/functions/FunctionInvokeDescriptor.kt

@@ -60,7 +60,8 @@ public class FunctionInvokeDescriptor private constructor(
                             .map { createValueParameter(result, it.index, it.value) },
                     typeParameters.last().getDefaultType(),
                     Modality.ABSTRACT,
-                    Visibilities.PUBLIC
+                    Visibilities.PUBLIC,
+                    true
             )
             return result
         }

core/descriptors/src/org/jetbrains/kotlin/descriptors/FunctionDescriptor.java

@@ -40,4 +40,6 @@ public interface FunctionDescriptor extends CallableMemberDescriptor {
     @NotNull
     @Override
     FunctionDescriptor copy(DeclarationDescriptor newOwner, Modality modality, Visibility visibility, Kind kind, boolean copyOverrides);
+
+    boolean isOperator();
 }

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/ConstructorDescriptorImpl.java

@@ -59,7 +59,8 @@ public class ConstructorDescriptorImpl extends FunctionDescriptorImpl implements
             @NotNull List<ValueParameterDescriptor> unsubstitutedValueParameters,
             @NotNull Visibility visibility
     ) {
-        super.initialize(null, calculateDispatchReceiverParameter(), typeParameters, unsubstitutedValueParameters, null, Modality.FINAL, visibility);
+        super.initialize(null, calculateDispatchReceiverParameter(), typeParameters, unsubstitutedValueParameters, null,
+                         Modality.FINAL, visibility, false);
         return this;
     }
 

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/FunctionDescriptorImpl.java

@@ -42,6 +42,7 @@ public abstract class FunctionDescriptorImpl extends DeclarationDescriptorNonRoo
     private ReceiverParameterDescriptor dispatchReceiverParameter;
     private Modality modality;
     private Visibility visibility = Visibilities.UNKNOWN;
+    private boolean isOperator;
     private final Set<FunctionDescriptor> overriddenFunctions = SmartSet.create();
     private final FunctionDescriptor original;
     private final Kind kind;
@@ -67,13 +68,15 @@ public abstract class FunctionDescriptorImpl extends DeclarationDescriptorNonRoo
             @NotNull List<ValueParameterDescriptor> unsubstitutedValueParameters,
             @Nullable JetType unsubstitutedReturnType,
             @Nullable Modality modality,
-            @NotNull Visibility visibility
+            @NotNull Visibility visibility,
+            boolean isOperator
     ) {
         this.typeParameters = UtilsPackage.toReadOnlyList(typeParameters);
         this.unsubstitutedValueParameters = unsubstitutedValueParameters;
         this.unsubstitutedReturnType = unsubstitutedReturnType;
         this.modality = modality;
         this.visibility = visibility;
+        this.isOperator = isOperator;
         this.extensionReceiverParameter = DescriptorFactory.createExtensionReceiverParameterForCallable(this, receiverParameterType);
         this.dispatchReceiverParameter = dispatchReceiverParameter;
         
@@ -138,6 +141,17 @@ public abstract class FunctionDescriptorImpl extends DeclarationDescriptorNonRoo
         return visibility;
     }
 
+    @Override
+    public boolean isOperator() {
+        if (isOperator) return true;
+
+        for (FunctionDescriptor descriptor : overriddenFunctions) {
+            if (descriptor.isOperator()) return true;
+        }
+
+        return false;
+    }
+
     @Override
     public void addOverriddenDescriptor(@NotNull CallableMemberDescriptor overriddenFunction) {
         overriddenFunctions.add((FunctionDescriptor) overriddenFunction);
@@ -187,7 +201,7 @@ public abstract class FunctionDescriptorImpl extends DeclarationDescriptorNonRoo
         if (originalSubstitutor.isEmpty()) {
             return this;
         }
-        return doSubstitute(originalSubstitutor, getContainingDeclaration(), modality, visibility, getOriginal(), true, getKind());
+        return doSubstitute(originalSubstitutor, getContainingDeclaration(), modality, visibility, isOperator, getOriginal(), true, getKind());
     }
 
     @Nullable
@@ -195,12 +209,13 @@ public abstract class FunctionDescriptorImpl extends DeclarationDescriptorNonRoo
             @NotNull DeclarationDescriptor newOwner,
             @NotNull Modality newModality,
             @NotNull Visibility newVisibility,
+            boolean isOperator,
             @Nullable FunctionDescriptor original,
             boolean copyOverrides,
             @NotNull Kind kind
     ) {
         return doSubstitute(originalSubstitutor,
-                newOwner, newModality, newVisibility, original, copyOverrides, kind,
+                newOwner, newModality, newVisibility, isOperator, original, copyOverrides, kind,
                 getValueParameters(), getExtensionReceiverParameterType(), getReturnType()
         );
     }
@@ -217,6 +232,7 @@ public abstract class FunctionDescriptorImpl extends DeclarationDescriptorNonRoo
             @NotNull DeclarationDescriptor newOwner,
             @NotNull Modality newModality,
             @NotNull Visibility newVisibility,
+            boolean isOperator,
             @Nullable FunctionDescriptor original,
             boolean copyOverrides,
             @NotNull Kind kind,
@@ -277,7 +293,8 @@ public abstract class FunctionDescriptorImpl extends DeclarationDescriptorNonRoo
                 substitutedValueParameters,
                 substitutedReturnType,
                 newModality,
-                newVisibility
+                newVisibility,
+                isOperator
         );
 
         if (copyOverrides) {

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/PropertyAccessorDescriptorImpl.java

@@ -73,6 +73,11 @@ public abstract class PropertyAccessorDescriptorImpl extends DeclarationDescript
         return kind;
     }
 
+    @Override
+    public boolean isOperator() {
+        return false;
+    }
+
     @NotNull
     @Override
     public FunctionDescriptor substitute(@NotNull TypeSubstitutor substitutor) {

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/ScriptCodeDescriptor.java

@@ -36,7 +36,8 @@ public class ScriptCodeDescriptor extends FunctionDescriptorImpl {
             @NotNull ReceiverParameterDescriptor dispatchReceiverParameter,
             @NotNull List<ValueParameterDescriptor> valueParameters,
             @NotNull JetType returnType) {
-        super.initialize(null, dispatchReceiverParameter, Collections.<TypeParameterDescriptor>emptyList(), valueParameters, returnType, Modality.FINAL, Visibilities.INTERNAL);
+        super.initialize(null, dispatchReceiverParameter, Collections.<TypeParameterDescriptor>emptyList(), valueParameters, returnType,
+                         Modality.FINAL, Visibilities.INTERNAL, /*isOperator =*/ false);
     }
 
     @NotNull

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/SimpleFunctionDescriptorImpl.java

@@ -58,10 +58,11 @@ public class SimpleFunctionDescriptorImpl extends FunctionDescriptorImpl impleme
             @NotNull List<ValueParameterDescriptor> unsubstitutedValueParameters,
             @Nullable JetType unsubstitutedReturnType,
             @Nullable Modality modality,
-            @NotNull Visibility visibility
+            @NotNull Visibility visibility,
+            boolean isOperator
     ) {
         super.initialize(receiverParameterType, dispatchReceiverParameter, typeParameters, unsubstitutedValueParameters,
-                         unsubstitutedReturnType, modality, visibility);
+                         unsubstitutedReturnType, modality, visibility, isOperator);
         return this;
     }
 
@@ -99,7 +100,7 @@ public class SimpleFunctionDescriptorImpl extends FunctionDescriptorImpl impleme
             boolean copyOverrides
     ) {
         return (SimpleFunctionDescriptorImpl) doSubstitute(
-                TypeSubstitutor.EMPTY, newOwner, modality, visibility, null, copyOverrides, kind
+                TypeSubstitutor.EMPTY, newOwner, modality, visibility, isOperator(), null, copyOverrides, kind
         );
     }
 }

core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererImpl.kt

@@ -461,6 +461,12 @@ internal class DescriptorRendererImpl(
         }
     }
 
+    private fun renderOperator(functionDescriptor: FunctionDescriptor, builder: StringBuilder) {
+        if (functionDescriptor.isOperator && functionDescriptor.overriddenDescriptors.none { it.isOperator }) {
+            builder.append("operator ")
+        }
+    }
+
     override fun render(declarationDescriptor: DeclarationDescriptor): String {
         return StringBuilder {
             declarationDescriptor.accept(RenderDeclarationDescriptorVisitor(), this)
@@ -548,6 +554,7 @@ internal class DescriptorRendererImpl(
             renderAnnotations(function, builder)
             renderVisibility(function.getVisibility(), builder)
             renderModalityForCallable(function, builder)
+            renderOperator(function, builder)
             renderOverride(function, builder)
             renderMemberKind(function, builder)
 

core/descriptors/src/org/jetbrains/kotlin/resolve/DescriptorFactory.java

@@ -102,8 +102,8 @@ public class DescriptorFactory {
                                                     CallableMemberDescriptor.Kind.SYNTHESIZED, enumClass.getSource());
         return values.initialize(null, null, Collections.<TypeParameterDescriptor>emptyList(),
                                  Collections.<ValueParameterDescriptor>emptyList(),
-                                 getBuiltIns(enumClass).getArrayType(Variance.INVARIANT, enumClass.getDefaultType()), Modality.FINAL,
+                                 getBuiltIns(enumClass).getArrayType(Variance.INVARIANT, enumClass.getDefaultType()),
-                                 Visibilities.PUBLIC);
+                                 Modality.FINAL, Visibilities.PUBLIC, false);
     }
 
     @NotNull
@@ -116,8 +116,8 @@ public class DescriptorFactory {
                 enumClass.getSource()
         );
         return valueOf.initialize(null, null, Collections.<TypeParameterDescriptor>emptyList(),
-                                  Collections.singletonList(parameterDescriptor), enumClass.getDefaultType(), Modality.FINAL,
+                                  Collections.singletonList(parameterDescriptor), enumClass.getDefaultType(),
-                                  Visibilities.PUBLIC);
+                                  Modality.FINAL, Visibilities.PUBLIC, false);
     }
 
     @Nullable

core/descriptors/src/org/jetbrains/kotlin/types/ErrorUtils.java

@@ -423,7 +423,8 @@ public class ErrorUtils {
                 Collections.<ValueParameterDescriptor>emptyList(), // TODO
                 createErrorType("<ERROR FUNCTION RETURN TYPE>"),
                 Modality.OPEN,
-                Visibilities.INTERNAL
+                Visibilities.INTERNAL,
+                false
         );
         return function;
     }

core/deserialization/src/descriptors.proto

@@ -252,6 +252,7 @@ message Callable {
      hasConstant
      isConst
      lateinit
+     isOperator
    */
   optional int32 flags = 1;
 

core/deserialization/src/org/jetbrains/kotlin/serialization/Flags.java

@@ -52,6 +52,8 @@ public class Flags {
 
     public static final FlagField<Boolean> LATE_INIT = FlagField.booleanAfter(IS_CONST);
 
+    public static final FlagField<Boolean> IS_OPERATOR = FlagField.booleanAfter(LATE_INIT);
+
     // Parameters
 
     public static final FlagField<Boolean> DECLARES_DEFAULT_VALUE = FlagField.booleanAfter(HAS_ANNOTATIONS);
@@ -118,7 +120,8 @@ public class Flags {
             boolean hasSetter,
             boolean hasConstant,
             boolean lateInit,
-            boolean isConst
+            boolean isConst,
+            boolean isOperator
     ) {
         return HAS_ANNOTATIONS.toFlags(hasAnnotations)
                | MODALITY.toFlags(modality(modality))
@@ -130,6 +133,7 @@ public class Flags {
                | HAS_CONSTANT.toFlags(hasConstant)
                | LATE_INIT.toFlags(lateInit)
                | IS_CONST.toFlags(isConst)
+               | IS_OPERATOR.toFlags(isOperator)
                ;
     }
 

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/MemberDeserializer.kt

@@ -148,9 +148,10 @@ public class MemberDeserializer(private val c: DeserializationContext) {
                 getDispatchReceiverParameter(),
                 local.typeDeserializer.ownTypeParameters,
                 local.memberDeserializer.valueParameters(proto, AnnotatedCallableKind.FUNCTION),
-                local.typeDeserializer.type(proto.getReturnType()),
+                local.typeDeserializer.type(proto.returnType),
-                Deserialization.modality(Flags.MODALITY.get(proto.getFlags())),
+                Deserialization.modality(Flags.MODALITY.get(proto.flags)),
-                Deserialization.visibility(Flags.VISIBILITY.get(proto.getFlags()))
+                Deserialization.visibility(Flags.VISIBILITY.get(proto.flags)),
+                Flags.IS_OPERATOR.get(proto.flags)
         )
         return function
     }

idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/stubBuilder/CallableClsStubBuilder.kt

@@ -98,7 +98,13 @@ private class CallableClsStubBuilder(
         val modalityModifiers = if (isModalityIrrelevant) listOf() else listOf(MODALITY)
         val constModifiers = if (callableKind == CallableKind.VAL) listOf(CONST) else listOf()
 
-        val relevantModifiers = listOf(VISIBILITY) + constModifiers + modalityModifiers
+        val additionalModifiers = when (callableKind) {
+            CallableKind.FUN -> arrayOf(OPERATOR)
+            CallableKind.VAL, CallableKind.VAR -> arrayOf(LATEINIT)
+            else -> emptyArray<FlagsToModifiers>()
+        }
+
+        val relevantModifiers = listOf(VISIBILITY) + constModifiers + modalityModifiers + additionalModifiers
         val modifierListStubImpl = createModifierListStubForDeclaration(
                 callableStub, callableProto.getFlags(), relevantModifiers
         )

idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/stubBuilder/clsStubBuilding.kt

@@ -191,6 +191,18 @@ enum class FlagsToModifiers {
         override fun getModifiers(flags: Int): JetModifierKeywordToken? {
             return if (Flags.IS_CONST.get(flags)) JetTokens.CONST_KEYWORD else null
         }
+    },
+
+    LATEINIT {
+        override fun getModifiers(flags: Int): JetModifierKeywordToken? {
+            return if (Flags.LATE_INIT.get(flags)) JetTokens.LATE_INIT_KEYWORD else null
+        }
+    },
+
+    OPERATOR {
+        override fun getModifiers(flags: Int): JetModifierKeywordToken? {
+            return if (Flags.IS_OPERATOR.get(flags)) JetTokens.OPERATOR_KEYWORD else null
+        }
     };
 
     abstract fun getModifiers(flags: Int): JetModifierKeywordToken?

idea/idea-completion/testData/keywords/AfterClassProperty.kt

@@ -34,6 +34,7 @@ class MouseMovedEventArgs
 // EXIST:  init
 /*why?*/
 // EXIST:  companion object
+// EXIST:  operator
 // EXIST:  sealed
 // EXIST:  lateinit
 // EXIST:  data

idea/idea-completion/testData/keywords/AfterClasses.kt

@@ -37,6 +37,7 @@ class B {
 // EXIST:  vararg
 /*why?*/
 // EXIST:  companion object
+// EXIST:  operator
 // EXIST:  sealed
 // EXIST:  lateinit
 // EXIST:  data

idea/idea-completion/testData/keywords/AfterFuns.kt

@@ -37,6 +37,7 @@ class A {
 // EXIST:  init
 /*why?*/
 // EXIST:  companion object
+// EXIST:  operator
 // EXIST:  sealed
 // EXIST:  lateinit
 // EXIST:  data

idea/idea-completion/testData/keywords/GlobalPropertyAccessors.kt

@@ -37,6 +37,7 @@ var a : Int
 // EXIST:  vararg
 /*why?*/
 // EXIST:  companion object
+// EXIST:  operator
 // EXIST:  sealed
 // EXIST:  lateinit
 // EXIST:  data

idea/idea-completion/testData/keywords/InClassBeforeFun.kt

@@ -35,6 +35,7 @@ public class Test {
 // EXIST:  init
 /*why?*/
 // EXIST:  companion object
+// EXIST:  operator
 // EXIST:  sealed
 // EXIST:  lateinit
 // EXIST:  data

idea/idea-completion/testData/keywords/InClassScope.kt

@@ -29,6 +29,7 @@ class TestClass {
 // EXIST:  constructor
 // EXIST:  init
 // EXIST:  companion object
+// EXIST:  operator
 // EXIST:  sealed
 // EXIST:  lateinit
 // EXIST:  data

idea/idea-completion/testData/keywords/InTopScopeAfterPackage.kt

@@ -28,6 +28,7 @@ package Test
 // EXIST:  vararg
 /*why?*/
 // EXIST:  companion object
+// EXIST:  operator
 // EXIST:  sealed
 // EXIST:  lateinit
 // EXIST:  data

idea/idea-completion/testData/keywords/PropertyAccessors.kt

@@ -33,6 +33,7 @@ class Some {
 // EXIST:  constructor
 // EXIST:  init
 // EXIST:  companion object
+// EXIST:  operator
 // EXIST:  sealed
 // EXIST:  lateinit
 // EXIST:  data

idea/idea-completion/testData/keywords/PropertyAccessors2.kt

@@ -33,6 +33,7 @@ class Some {
 // EXIST:  constructor
 // EXIST:  init
 // EXIST:  companion object
+// EXIST:  operator
 // EXIST:  sealed
 // EXIST:  lateinit
 // EXIST:  data

idea/idea-completion/testData/keywords/PropertySetter.kt

@@ -35,6 +35,7 @@ class Some {
 // EXIST:  constructor
 // EXIST:  init
 // EXIST:  companion object
+// EXIST:  operator
 // EXIST:  sealed
 // EXIST:  lateinit
 // EXIST:  data

idea/idea-completion/testData/keywords/TopScope.kt

@@ -27,6 +27,7 @@
 // EXIST:  vararg
 /*why?*/
 // EXIST:  companion object
+// EXIST:  operator
 // EXIST:  sealed
 // EXIST: lateinit
 // EXIST:  data

idea/src/org/jetbrains/kotlin/idea/quickfix/createFromUsage/callableBuilder/CallableBuilder.kt

@@ -415,7 +415,7 @@ class CallableBuilder(val config: CallableBuilderConfiguration) {
                 )
             }
 
-            return fakeFunction.initialize(null, null, typeParameters, Collections.emptyList(), null, null, Visibilities.INTERNAL)
+            return fakeFunction.initialize(null, null, typeParameters, Collections.emptyList(), null, null, Visibilities.INTERNAL, false)
         }
 
         private fun renderTypeCandidates(

idea/tests/org/jetbrains/kotlin/idea/stubs/ResolveByStubTestGenerated.java

@@ -2185,6 +2185,12 @@ public class ResolveByStubTestGenerated extends AbstractResolveByStubTest {
             doTest(fileName);
         }
 
+        @TestMetadata("OperatorKeyword.kt")
+        public void testOperatorKeyword() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/loadJava/compiledKotlin/fun/OperatorKeyword.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("PropagateDeepSubclass.kt")
         public void testPropagateDeepSubclass() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/loadJava/compiledKotlin/fun/PropagateDeepSubclass.kt");