"trait" modifier supported

idea/src/org/jetbrains/jet/lang/descriptors/ClassDescriptor.java

@@ -47,4 +47,6 @@ public interface ClassDescriptor extends ClassifierDescriptor {
     boolean isAbstract();
 
     boolean isOpen();
+
+    boolean isTrait();
 }

idea/src/org/jetbrains/jet/lang/descriptors/ClassDescriptorImpl.java

@@ -125,4 +125,9 @@ public class ClassDescriptorImpl extends DeclarationDescriptorImpl implements Cl
     public boolean isOpen() {
         return false;
     }
+
+    @Override
+    public boolean isTrait() {
+        return false;
+    }
 }

idea/src/org/jetbrains/jet/lang/descriptors/LazySubstitutingClassDescriptor.java

@@ -149,6 +149,11 @@ public class LazySubstitutingClassDescriptor implements ClassDescriptor {
         return original.isOpen();
     }
 
+    @Override
+    public boolean isTrait() {
+        return original.isTrait();
+    }
+
     @Override
     public boolean isClassObjectAValue() {
         return original.isClassObjectAValue();

idea/src/org/jetbrains/jet/lang/descriptors/MutableClassDescriptor.java

@@ -24,6 +24,7 @@ public class MutableClassDescriptor extends MutableDeclarationDescriptor impleme
 
     private boolean open;
     private boolean isAbstract;
+    private boolean trait;
     private TypeConstructor typeConstructor;
     private final WritableScope scopeForMemberResolution;
     private final WritableScope scopeForMemberLookup;
@@ -151,6 +152,15 @@ public class MutableClassDescriptor extends MutableDeclarationDescriptor impleme
         this.isAbstract = isAbstract;
     }
 
+    @Override
+    public boolean isTrait() {
+        return trait;
+    }
+
+    public void setTrait(boolean trait) {
+        this.trait = trait;
+    }
+
     public boolean isOpen() {
         return open;
     }

idea/src/org/jetbrains/jet/lang/resolve/ClassDescriptorResolver.java

@@ -147,6 +147,7 @@ public class ClassDescriptorResolver {
 
         descriptor.setOpen(classElement.hasModifier(JetTokens.OPEN_KEYWORD) || classElement.hasModifier(JetTokens.ABSTRACT_KEYWORD));
         descriptor.setAbstract(classElement.hasModifier(JetTokens.ABSTRACT_KEYWORD));
+        descriptor.setTrait(classElement.hasModifier(JetTokens.TRAIT_KEYWORD));
 
         trace.record(BindingContext.CLASS, classElement, descriptor);
     }

idea/src/org/jetbrains/jet/lang/resolve/java/JavaClassDescriptor.java

@@ -20,6 +20,9 @@ public class JavaClassDescriptor extends MutableDeclarationDescriptor implements
     private JavaClassMembersScope unsubstitutedMemberScope;
     private JetType classObjectType;
     private final WritableFunctionGroup constructors = new WritableFunctionGroup("<init>");
+    private boolean isAbstract;
+    private boolean isOpen;
+    private boolean isTrait;
 
     public JavaClassDescriptor(DeclarationDescriptor containingDeclaration) {
         super(containingDeclaration);
@@ -29,6 +32,12 @@ public class JavaClassDescriptor extends MutableDeclarationDescriptor implements
         this.typeConstructor = typeConstructor;
     }
 
+    public void setModifiers(boolean isAbstract, boolean isOpen, boolean isTrait) {
+        this.isAbstract = isAbstract;
+        this.isOpen = isOpen;
+        this.isTrait = isTrait;
+    }
+
     public void setUnsubstitutedMemberScope(JavaClassMembersScope memberScope) {
         this.unsubstitutedMemberScope = memberScope;
     }
@@ -110,6 +119,11 @@ public class JavaClassDescriptor extends MutableDeclarationDescriptor implements
         return classObjectType;
     }
 
+    @Override
+    public boolean isClassObjectAValue() {
+        return false;
+    }
+
     @Override
     public boolean isObject() {
         return false;
@@ -117,17 +131,17 @@ public class JavaClassDescriptor extends MutableDeclarationDescriptor implements
 
     @Override
     public boolean isAbstract() {
-        return false;
+        return isAbstract;
     }
 
     @Override
     public boolean isOpen() {
-        return false;
+        return isOpen;
     }
 
     @Override
-    public boolean isClassObjectAValue() {
-        return false;
+    public boolean isTrait() {
+        return isTrait;
     }
 
     @Override

idea/src/org/jetbrains/jet/lang/resolve/java/JavaDescriptorResolver.java

@@ -106,6 +106,11 @@ public class JavaDescriptorResolver {
                 supertypes
 
         ));
+        classDescriptor.setModifiers(
+                psiClass.hasModifierProperty(PsiModifier.ABSTRACT),
+                !psiClass.hasModifierProperty(PsiModifier.FINAL),
+                psiClass.isInterface()
+        );
         classDescriptorCache.put(psiClass.getQualifiedName(), classDescriptor);
         classDescriptor.setUnsubstitutedMemberScope(new JavaClassMembersScope(classDescriptor, psiClass, semanticServices, false));
         classDescriptor.setClassObjectMemberScope(new JavaClassMembersScope(classDescriptor, psiClass, semanticServices, true));

idea/src/org/jetbrains/jet/lexer/JetTokens.java

@@ -136,6 +136,7 @@ public interface JetTokens {
     JetKeywordToken PROTECTED_KEYWORD = JetKeywordToken.softKeyword("protected");
     JetKeywordToken CATCH_KEYWORD     = JetKeywordToken.softKeyword("catch");
     JetKeywordToken OUT_KEYWORD       = JetKeywordToken.softKeyword("out");
+    JetKeywordToken TRAIT_KEYWORD     = JetKeywordToken.softKeyword("trait");
 
     JetKeywordToken FINALLY_KEYWORD   = JetKeywordToken.softKeyword("finally");
 
@@ -154,12 +155,12 @@ public interface JetTokens {
     TokenSet SOFT_KEYWORDS = TokenSet.create(WRAPS_KEYWORD, IMPORT_KEYWORD, WHERE_KEYWORD, BY_KEYWORD, GET_KEYWORD,
             SET_KEYWORD, ABSTRACT_KEYWORD, VIRTUAL_KEYWORD, ENUM_KEYWORD, OPEN_KEYWORD, ATTRIBUTE_KEYWORD,
             OVERRIDE_KEYWORD, PRIVATE_KEYWORD, PUBLIC_KEYWORD, INTERNAL_KEYWORD, PROTECTED_KEYWORD,
-            CATCH_KEYWORD, FINALLY_KEYWORD, REF_KEYWORD, OUT_KEYWORD
+            CATCH_KEYWORD, FINALLY_KEYWORD, REF_KEYWORD, OUT_KEYWORD, TRAIT_KEYWORD
     );
 
     TokenSet MODIFIER_KEYWORDS = TokenSet.create(ABSTRACT_KEYWORD, VIRTUAL_KEYWORD, ENUM_KEYWORD,
             OPEN_KEYWORD, ATTRIBUTE_KEYWORD, OVERRIDE_KEYWORD, PRIVATE_KEYWORD, PUBLIC_KEYWORD, INTERNAL_KEYWORD,
-            PROTECTED_KEYWORD, REF_KEYWORD, OUT_KEYWORD, IN_KEYWORD
+            PROTECTED_KEYWORD, REF_KEYWORD, OUT_KEYWORD, IN_KEYWORD, TRAIT_KEYWORD
     );
     TokenSet WHITE_SPACE_OR_COMMENT_BIT_SET = TokenSet.create(WHITE_SPACE, BLOCK_COMMENT, EOL_COMMENT, DOC_COMMENT);
     TokenSet WHITESPACES = TokenSet.create(TokenType.WHITE_SPACE);

idea/src/org/jetbrains/jet/resolve/DescriptorRenderer.java

@@ -251,7 +251,7 @@ public class DescriptorRenderer {
 
         @Override
         public Void visitClassDescriptor(ClassDescriptor descriptor, StringBuilder builder) {
-            String keyword = "class";
+            String keyword = descriptor.isTrait() ? "trait class" : "class";
             renderClassDescriptor(descriptor, builder, keyword);
             return super.visitClassDescriptor(descriptor, builder);
         }