Extract function: add default name for parameter

idea/src/org/jetbrains/jet/plugin/refactoring/extractFunction/extractableAnalysisUtil.kt

@@ -610,7 +610,7 @@ private fun ExtractionData.inferParametersInfo(
 
         with (parameter) {
             if (currentName == null) {
-                currentName = JetNameSuggester.suggestNames(parameterType, varNameValidator, null).first()
+                currentName = JetNameSuggester.suggestNames(parameterType, varNameValidator, "p").first()
             }
             mirrorVarName = if (descriptorToExtract in modifiedVarDescriptors) varNameValidator.validateName(name) else null
             info.parameters.add(this)

idea/testData/refactoring/extractFunction/basic/extensionFunForArray.kt

@@ -0,0 +1,6 @@
+// PARAM_TYPES: kotlin.Array<T>, kotlin.Cloneable, Any
+// PARAM_DESCRIPTOR: internal fun <T> kotlin.Array<T>.test(): kotlin.Unit defined in root package
+// SIBLING:
+fun <T> Array<T>.test() {
+    <selection>this.isEmpty()</selection>
+}

idea/testData/refactoring/extractFunction/basic/extensionFunForArray.kt.after

@@ -0,0 +1,10 @@
+// PARAM_TYPES: kotlin.Array<T>, kotlin.Cloneable, Any
+// PARAM_DESCRIPTOR: internal fun <T> kotlin.Array<T>.test(): kotlin.Unit defined in root package
+// SIBLING:
+fun <T> Array<T>.test() {
+    unit()
+}
+
+private fun <T> Array<T>.unit() {
+    this.isEmpty()
+}

idea/tests/org/jetbrains/jet/plugin/refactoring/introduce/introduceVariable/JetExtractionTestGenerated.java

@@ -354,6 +354,12 @@ public class JetExtractionTestGenerated extends AbstractJetExtractionTest {
                 JetTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("idea/testData/refactoring/extractFunction/basic"), Pattern.compile("^(.+)\\.kt$"), true);
             }
 
+            @TestMetadata("extensionFunForArray.kt")
+            public void testExtensionFunForArray() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("idea/testData/refactoring/extractFunction/basic/extensionFunForArray.kt");
+                doExtractFunctionTest(fileName);
+            }
+
             @TestMetadata("fragmentWithComment.kt")
             public void testFragmentWithComment() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("idea/testData/refactoring/extractFunction/basic/fragmentWithComment.kt");