Make JetSimpleNameExpression abstract, create subclasses for each element type

It's not a good practice to have one PSI class to correspond to several element types

compiler/frontend/src/org/jetbrains/jet/JetNodeTypes.java

@@ -115,9 +115,9 @@ public interface JetNodeTypes {
     JetNodeType FUNCTION_LITERAL          = new JetNodeType("FUNCTION_LITERAL", JetFunctionLiteral.class);
     JetNodeType ANNOTATED_EXPRESSION      = new JetNodeType("ANNOTATED_EXPRESSION", JetAnnotatedExpression.class);
 
-    JetNodeType REFERENCE_EXPRESSION      = new JetNodeType("REFERENCE_EXPRESSION", JetSimpleNameExpression.class);
-    JetNodeType OPERATION_REFERENCE       = new JetNodeType("OPERATION_REFERENCE", JetSimpleNameExpression.class);
-    JetNodeType LABEL                     = new JetNodeType("LABEL", JetSimpleNameExpression.class);
+    JetNodeType REFERENCE_EXPRESSION      = new JetNodeType("REFERENCE_EXPRESSION", JetNameReferenceExpression.class);
+    JetNodeType OPERATION_REFERENCE       = new JetNodeType("OPERATION_REFERENCE", JetOperationReferenceExpression.class);
+    JetNodeType LABEL                     = new JetNodeType("LABEL", JetLabelReferenceExpression.class);
 
     JetNodeType LABEL_QUALIFIER           = new JetNodeType("LABEL_QUALIFIER", JetContainerNode.class);
 

compiler/frontend/src/org/jetbrains/jet/lang/psi/JetLabelReferenceExpression.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2010-2014 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.jet.lang.psi;
+
+import com.intellij.lang.ASTNode;
+import org.jetbrains.annotations.NotNull;
+
+public class JetLabelReferenceExpression extends JetSimpleNameExpression {
+    public JetLabelReferenceExpression(@NotNull ASTNode node) {
+        super(node);
+    }
+}

compiler/frontend/src/org/jetbrains/jet/lang/psi/JetNameReferenceExpression.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2010-2014 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.jet.lang.psi;
+
+import com.intellij.lang.ASTNode;
+import org.jetbrains.annotations.NotNull;
+
+public class JetNameReferenceExpression extends JetSimpleNameExpression {
+    public JetNameReferenceExpression(@NotNull ASTNode node) {
+        super(node);
+    }
+}

compiler/frontend/src/org/jetbrains/jet/lang/psi/JetOperationReferenceExpression.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2010-2014 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.jet.lang.psi;
+
+import com.intellij.lang.ASTNode;
+import org.jetbrains.annotations.NotNull;
+
+public class JetOperationReferenceExpression extends JetSimpleNameExpression {
+    public JetOperationReferenceExpression(@NotNull ASTNode node) {
+        super(node);
+    }
+}

compiler/frontend/src/org/jetbrains/jet/lang/psi/JetSimpleNameExpression.java

@@ -29,7 +29,7 @@ import org.jetbrains.jet.lexer.JetTokens;
 
 import static org.jetbrains.jet.lexer.JetTokens.*;
 
-public class JetSimpleNameExpression extends JetReferenceExpression {
+public abstract class JetSimpleNameExpression extends JetReferenceExpression {
     public static final TokenSet REFERENCE_TOKENS = TokenSet.create(LABEL_IDENTIFIER, IDENTIFIER, FIELD_IDENTIFIER, THIS_KEYWORD, SUPER_KEYWORD);
 
     public JetSimpleNameExpression(@NotNull ASTNode node) {