KT-1328 removing single class from file, should remove file too. Also changed file icon to one of containing classes icon.

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

@@ -19,6 +19,7 @@ package org.jetbrains.jet.lang.psi;
 import com.intellij.lang.ASTNode;
 import com.intellij.psi.StubBasedPsiElement;
 import com.intellij.psi.stubs.IStubElementType;
+import com.intellij.util.IncorrectOperationException;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.JetNodeTypes;
@@ -153,4 +154,9 @@ public class JetClass extends JetTypeParameterListOwner
         // TODO (stubs)
         return null;
     }
+
+    @Override
+    public void delete() throws IncorrectOperationException {
+        JetPsiUtil.deleteClass(this);
+    }
 }

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

@@ -117,5 +117,10 @@ public class JetObjectDeclaration extends JetNamedDeclaration implements JetClas
     @NotNull
     public PsiElement getObjectKeyword() {
         return findChildByType(JetTokens.OBJECT_KEYWORD);
-    }     
+    }
+
+    @Override
+    public void delete() throws IncorrectOperationException {
+        JetPsiUtil.deleteClass(this);
+    }
 }

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

@@ -17,6 +17,9 @@
 package org.jetbrains.jet.lang.psi;
 
 import com.intellij.psi.PsiElement;
+import com.intellij.psi.PsiFile;
+import com.intellij.psi.impl.CheckUtil;
+import com.intellij.psi.impl.source.codeStyle.CodeEditUtil;
 import com.intellij.psi.util.PsiTreeUtil;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -234,4 +237,16 @@ public class JetPsiUtil {
         return false;
     }
 
+    public static void deleteClass(@NotNull JetClassOrObject clazz) {
+        CheckUtil.checkWritable(clazz);
+        JetFile file = (JetFile) clazz.getContainingFile();
+        List<JetDeclaration> declarations = file.getDeclarations();
+        if (declarations.size() == 1) {
+            file.delete();
+        } else {
+            PsiElement parent = clazz.getParent();
+            CodeEditUtil.removeChild(parent.getNode(), clazz.getNode());
+        }
+    }
+
 }

idea/src/org/jetbrains/jet/plugin/JetIconProvider.java

@@ -19,6 +19,7 @@ package org.jetbrains.jet.plugin;
 import com.intellij.ide.IconProvider;
 import com.intellij.openapi.util.IconLoader;
 import com.intellij.openapi.util.Iconable;
+import com.intellij.openapi.util.text.StringUtil;
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.util.PlatformIcons;
@@ -27,6 +28,7 @@ import org.jetbrains.jet.lang.psi.*;
 import org.jetbrains.jet.lexer.JetTokens;
 
 import javax.swing.*;
+import java.util.List;
 
 /**
  * @author yole
@@ -38,6 +40,23 @@ public class JetIconProvider extends IconProvider {
     @Override
     public Icon getIcon(@NotNull PsiElement psiElement, int flags) {
         if (psiElement instanceof JetFile) {
+            JetFile file = (JetFile) psiElement;
+            List<JetDeclaration> declarations = file.getDeclarations();
+            JetClassOrObject mostImportantClass = null;
+            String nameWithoutExtension = StringUtil.getPackageName(file.getName());
+            for (JetDeclaration declaration : declarations) {
+                if (mostImportantClass == null && declaration instanceof JetClassOrObject) {
+                    mostImportantClass = (JetClassOrObject) declaration;
+                } else if (declaration instanceof JetClassOrObject) {
+                    JetClassOrObject object = (JetClassOrObject) declaration;
+                    if (nameWithoutExtension.equals(object.getName())) {
+                        mostImportantClass = object;
+                    }
+                }
+            }
+            if (mostImportantClass != null) {
+                return getIcon(mostImportantClass, flags);
+            }
             return KOTLIN_ICON;
         }
         if (psiElement instanceof JetNamespaceHeader) {