Introduce constant for "kt".

compiler/frontend/src/org/jetbrains/jet/plugin/JetFileType.java

@@ -24,7 +24,9 @@ import org.jetbrains.annotations.NotNull;
 import javax.swing.*;
 
 public class JetFileType extends LanguageFileType {
+    public static final String EXTENSION = "kt";
     public static final JetFileType INSTANCE = new JetFileType();
+
     private final NotNullLazyValue<Icon> myIcon = new NotNullLazyValue<Icon>() {
         @NotNull
         @Override
@@ -52,7 +54,7 @@ public class JetFileType extends LanguageFileType {
     @Override
     @NotNull
     public String getDefaultExtension() {
-        return "kt";
+        return EXTENSION;
     }
 
     @Override

idea/idea-analysis/src/org/jetbrains/jet/plugin/framework/JsHeaderLibraryDetectionUtil.java

@@ -36,7 +36,7 @@ public class JsHeaderLibraryDetectionUtil {
                 @Override
                 protected boolean accept(VirtualFile file) {
                     String extension = file.getExtension();
-                    return extension != null && extension.equals(JetFileType.INSTANCE.getDefaultExtension());
+                    return extension != null && extension.equals(JetFileType.EXTENSION);
                 }
             };
 

idea/src/org/jetbrains/jet/plugin/refactoring/extractFunction/ui/KotlinFunctionSignatureComponent.kt

@@ -23,7 +23,7 @@ import com.intellij.refactoring.ui.MethodSignatureComponent
 public class KotlinFunctionSignatureComponent(
         signature: String, project: Project
 ) : MethodSignatureComponent(signature, project, JetFileType.INSTANCE) {
-    private val myFileName = "dummy." + JetFileType.INSTANCE.getDefaultExtension()
+    private val myFileName = "dummy." + JetFileType.EXTENSION
 
     override fun getFileName(): String = myFileName
 }

idea/src/org/jetbrains/jet/plugin/refactoring/move/moveUtils.kt

@@ -168,7 +168,7 @@ fun createMoveUsageInfo(
 
 public fun JetNamedDeclaration.getFileNameAfterMove(): String? {
     return (getContainingFile() as? JetFile)?.let { file ->
-        if (file.getDeclarations().size > 1) "${getName()}.${JetFileType.INSTANCE.getDefaultExtension()}" else file.getName()
+        if (file.getDeclarations().size > 1) "${getName()}.${JetFileType.EXTENSION}" else file.getName()
     }
 }