Allow default object to be denoted with 'default' modifier

Report 'default' modifier in illegal positions

compiler/frontend/src/org/jetbrains/kotlin/psi/JetObjectDeclaration.java

@@ -91,7 +91,7 @@ public class JetObjectDeclaration extends JetNamedDeclarationStub<KotlinObjectSt
         if (stub != null) {
             return stub.isDefault();
         }
-        return getClassKeyword() != null;
+        return getClassKeyword() != null || hasModifier(JetTokens.DEFAULT_KEYWORD);
     }
 
     @Override

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

@@ -39,6 +39,7 @@ import java.util.*;
 
 import static org.jetbrains.kotlin.diagnostics.Errors.*;
 import static org.jetbrains.kotlin.lexer.JetTokens.*;
+import static org.jetbrains.kotlin.psi.JetStubbedPsiUtil.getContainingDeclaration;
 import static org.jetbrains.kotlin.resolve.DescriptorUtils.isDefaultObject;
 import static org.jetbrains.kotlin.resolve.DescriptorUtils.isEnumEntry;
 
@@ -141,6 +142,7 @@ public class ModifiersChecker {
         }
         else {
             checkInnerModifier(modifierListOwner, descriptor);
+            checkDefaultModifier(modifierListOwner);
             checkModalityModifiers(modifierListOwner);
             checkVisibilityModifiers(modifierListOwner, descriptor);
             checkVarianceModifiersOfTypeParameters(modifierListOwner);
@@ -232,6 +234,24 @@ public class ModifiersChecker {
         IN_OBJECT,
     }
 
+    private void checkDefaultModifier(@NotNull JetDeclaration declaration) {
+        if (declaration.hasModifier(DEFAULT_KEYWORD) && !isDefaultModifierAllowed(declaration)) {
+            reportIllegalModifiers(declaration, Collections.singletonList(DEFAULT_KEYWORD));
+        }
+    }
+
+    // NOTE: just checks if this is legal context for default modifier (Default object descriptor can be created)
+    // DEFAULT_OBJECT_NOT_ALLOWED can be reported later
+    public static boolean isDefaultModifierAllowed(@NotNull JetDeclaration declaration) {
+        if (declaration instanceof JetObjectDeclaration) {
+            JetDeclaration containingDeclaration = getContainingDeclaration(declaration);
+            if (containingDeclaration instanceof JetClassOrObject) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     @NotNull
     private static InnerModifierCheckResult checkIllegalInner(DeclarationDescriptor descriptor) {
         if (!(descriptor instanceof ClassDescriptor)) return InnerModifierCheckResult.ILLEGAL_POSITION;

compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/data/JetClassOrObjectInfo.java

@@ -20,9 +20,9 @@ import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiFile;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jetbrains.kotlin.name.FqName;
 import org.jetbrains.kotlin.name.Name;
 import org.jetbrains.kotlin.psi.*;
-import org.jetbrains.kotlin.name.FqName;
 
 import java.util.Collections;
 import java.util.List;

compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/data/JetObjectInfo.java

@@ -22,6 +22,7 @@ import org.jetbrains.kotlin.descriptors.ClassKind;
 import org.jetbrains.kotlin.psi.JetObjectDeclaration;
 import org.jetbrains.kotlin.psi.JetParameter;
 import org.jetbrains.kotlin.psi.JetTypeParameterList;
+import org.jetbrains.kotlin.resolve.ModifiersChecker;
 
 import java.util.Collections;
 import java.util.List;
@@ -54,6 +55,6 @@ public class JetObjectInfo extends JetClassOrObjectInfo<JetObjectDeclaration> {
     }
 
     public boolean isDefaultObject() {
-        return element.isDefault();
+        return element.isDefault() && ModifiersChecker.isDefaultModifierAllowed(element);
     }
 }