Create empty method for annotated properties w/o fields

There was no place in bytecode where annotations on properties without backing
fields could be stored to. Now they're written on a synthetic empty void method
with a special name ("propertyName$annotations").

(Annotations on properties cannot simply be written on getters in bytecode,
since a getter can have annotations of its own.)

compiler/backend/src/org/jetbrains/jet/codegen/PropertyCodegen.java

@@ -21,6 +21,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.asm4.FieldVisitor;
 import org.jetbrains.asm4.MethodVisitor;
+import org.jetbrains.asm4.Opcodes;
 import org.jetbrains.asm4.Type;
 import org.jetbrains.asm4.commons.InstructionAdapter;
 import org.jetbrains.jet.codegen.context.CodegenContext;
@@ -117,8 +118,7 @@ public class PropertyCodegen extends GenerationStateAware {
     }
 
     private void generateBackingField(JetNamedDeclaration p, PropertyDescriptor propertyDescriptor) {
-        //noinspection ConstantConditions
+        boolean hasBackingField = Boolean.TRUE.equals(bindingContext.get(BindingContext.BACKING_FIELD_REQUIRED, propertyDescriptor));
-        boolean hasBackingField = bindingContext.get(BindingContext.BACKING_FIELD_REQUIRED, propertyDescriptor);
         boolean isDelegated = p instanceof JetProperty && ((JetProperty) p).getDelegateExpression() != null;
         if (hasBackingField || isDelegated) {
             DeclarationDescriptor containingDeclaration = propertyDescriptor.getContainingDeclaration();
@@ -132,7 +132,20 @@ public class PropertyCodegen extends GenerationStateAware {
 
             AnnotationCodegen.forField(fieldVisitor, typeMapper).genAnnotations(propertyDescriptor);
         }
-
+        else if (!propertyDescriptor.getAnnotations().isEmpty()) {
+            // Annotations on properties without backing fields are stored in bytecode on an empty synthetic method. This way they're still
+            // accessible via reflection, and 'deprecated' and 'private' flags prevent this method from being called accidentally
+            MethodVisitor mv = v.newMethod(null,
+                                           ACC_DEPRECATED | ACC_FINAL | ACC_PRIVATE | ACC_STATIC | ACC_SYNTHETIC,
+                                           JvmAbi.getSyntheticMethodNameForAnnotatedProperty(propertyDescriptor.getName()),
+                                           JvmAbi.ANNOTATED_PROPERTY_METHOD_SIGNATURE,
+                                           null,
+                                           null);
+            AnnotationCodegen.forMethod(mv, typeMapper).genAnnotations(propertyDescriptor);
+            mv.visitCode();
+            mv.visitInsn(Opcodes.RETURN);
+            mv.visitEnd();
+        }
     }
 
     private FieldVisitor generateBackingField(JetNamedDeclaration element, PropertyDescriptor propertyDescriptor, boolean isDelegate, JetType jetType, Object defaultValue) {

compiler/frontend.java/src/org/jetbrains/jet/lang/resolve/java/JvmAbi.java

@@ -17,7 +17,6 @@
 package org.jetbrains.jet.lang.resolve.java;
 
 import org.jetbrains.annotations.NotNull;
-import org.jetbrains.jet.lang.descriptors.PropertyDescriptor;
 import org.jetbrains.jet.lang.resolve.name.FqName;
 import org.jetbrains.jet.lang.resolve.name.Name;
 
@@ -38,11 +37,12 @@ public class JvmAbi {
     public static final String CLASS_OBJECT_CLASS_NAME = "object";
     public static final String CLASS_OBJECT_SUFFIX = "$" + CLASS_OBJECT_CLASS_NAME;
 
-    public static final String DELEGATED_PROPERTY_NAME_POSTFIX = "$delegate";
+    public static final String DELEGATED_PROPERTY_NAME_SUFFIX = "$delegate";
+    public static final String ANNOTATED_PROPERTY_METHOD_NAME_SUFFIX = "$annotations";
+    public static final String ANNOTATED_PROPERTY_METHOD_SIGNATURE = "()V";
 
     public static final String INSTANCE_FIELD = "instance$";
     public static final String CLASS_OBJECT_FIELD = "object$";
-    public static final String RECEIVER_PARAMETER = "$receiver";
 
     public static final JvmClassName JETBRAINS_NOT_NULL_ANNOTATION =
             JvmClassName.byFqNameWithoutInnerClasses("org.jetbrains.annotations.NotNull");
@@ -56,12 +56,18 @@ public class JvmAbi {
         return fqName.lastSegmentIs(Name.identifier(CLASS_OBJECT_CLASS_NAME));
     }
 
+    @NotNull
     public static String getPropertyDelegateName(@NotNull Name name) {
-        return name.asString() + DELEGATED_PROPERTY_NAME_POSTFIX;
+        return name.asString() + DELEGATED_PROPERTY_NAME_SUFFIX;
     }
 
+    @NotNull
+    public static String getSyntheticMethodNameForAnnotatedProperty(@NotNull Name propertyName) {
+        return propertyName.asString() + ANNOTATED_PROPERTY_METHOD_NAME_SUFFIX;
+    }
 
-    public static String getDefaultPropertyName(Name propertyName, boolean isDelegated, boolean isExtensionProperty) {
+    @NotNull
+    public static String getDefaultPropertyName(@NotNull Name propertyName, boolean isDelegated, boolean isExtensionProperty) {
         if (isDelegated) {
             return getPropertyDelegateName(propertyName);
         }

compiler/testData/codegen/properties/annotatedClassPropertyNoField.kt

@@ -0,0 +1,8 @@
+import java.lang.annotation.*
+
+Retention(RetentionPolicy.RUNTIME) annotation class SomeAnnotation(val value: String)
+
+class A {
+    [SomeAnnotation("OK")] val property: Int
+        get() = 42
+}

compiler/testData/codegen/properties/annotatedPackagePropertyNoField.kt

@@ -0,0 +1,6 @@
+import java.lang.annotation.*
+
+Retention(RetentionPolicy.RUNTIME) annotation class SomeAnnotation(val value: String)
+
+[SomeAnnotation("OK")] val property: Int
+    get() = 42

compiler/tests/org/jetbrains/jet/codegen/PropertyGenTest.java

@@ -19,7 +19,12 @@ package org.jetbrains.jet.codegen;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.asm4.Opcodes;
 import org.jetbrains.jet.ConfigurationKind;
+import org.jetbrains.jet.lang.resolve.java.JvmAbi;
+import org.jetbrains.jet.lang.resolve.java.PackageClassUtils;
+import org.jetbrains.jet.lang.resolve.name.FqName;
+import org.jetbrains.jet.lang.resolve.name.Name;
 
+import java.lang.annotation.Annotation;
 import java.lang.reflect.*;
 
 import static org.jetbrains.jet.codegen.CodegenTestUtil.assertIsCurrentTime;
@@ -259,4 +264,41 @@ public class PropertyGenTest extends CodegenTestCase {
             throw new RuntimeException(e);
         }
     }
+
+    private static final String TEST_SYNTHETIC_METHOD_NAME = JvmAbi.getSyntheticMethodNameForAnnotatedProperty(Name.identifier("property"));
+
+    public void testAnnotatedClassPropertyNoField() {
+        loadFile("properties/annotatedClassPropertyNoField.kt");
+        assertClassHasAnnotatedSyntheticMethod(generateClass("A"));
+    }
+
+    public void testAnnotatedPackagePropertyNoField() {
+        loadFile("properties/annotatedPackagePropertyNoField.kt");
+        String packageClassName = PackageClassUtils.getPackageClassName(FqName.ROOT);
+        for (String fileName : generateClassesInFile().files()) {
+            if (fileName.startsWith(packageClassName) && !fileName.equals(packageClassName + ".class")) {
+                // This should be package$src class
+                Class<?> a = generateClass(fileName.substring(0, fileName.length() - ".class".length()));
+                assertClassHasAnnotatedSyntheticMethod(a);
+            }
+        }
+    }
+
+    private static void assertClassHasAnnotatedSyntheticMethod(@NotNull Class<?> a) {
+        for (Method method : a.getDeclaredMethods()) {
+            if (TEST_SYNTHETIC_METHOD_NAME.equals(method.getName())) {
+                assertTrue(method.isSynthetic());
+                int modifiers = method.getModifiers();
+                assertTrue(Modifier.isFinal(modifiers));
+                assertTrue(Modifier.isStatic(modifiers));
+                assertTrue(Modifier.isPrivate(modifiers));
+
+                Annotation[] annotations = method.getDeclaredAnnotations();
+                assertSize(1, annotations);
+                assertEquals("@SomeAnnotation(value=OK)", annotations[0].toString());
+                return;
+            }
+        }
+        fail("Synthetic method for annotated property not found: " + TEST_SYNTHETIC_METHOD_NAME);
+    }
 }