Change Signature: Use correct index in getOriginalParameter()

#KT-18642 Fixed
 #KT-18606 Fixed

idea/src/org/jetbrains/kotlin/idea/refactoring/changeSignature/KotlinParameterInfo.kt

@@ -191,9 +191,7 @@ class KotlinParameterInfo @JvmOverloads constructor (
     }
 
     private fun getOriginalParameter(inheritedCallable: KotlinCallableDefinitionUsage<*>): KtParameter? {
-        val currentFunction = inheritedCallable.declaration as? KtFunction ?: return null
-        val originalParameterIndex = if (currentFunction.receiverTypeReference == null) originalIndex else originalIndex - 1
-        return currentFunction.valueParameters.getOrNull(originalParameterIndex)
+        return (inheritedCallable.declaration as? KtFunction)?.valueParameters?.getOrNull(originalIndex)
     }
 
     private fun buildNewParameter(inheritedCallable: KotlinCallableDefinitionUsage<*>, parameterIndex: Int): KtParameter {

idea/testData/intentions/convertReceiverToParameter/varargs.kt

@@ -0,0 +1 @@
+fun <caret>Int.f1(vararg i: Int){}

idea/testData/intentions/convertReceiverToParameter/varargs.kt.after

@@ -0,0 +1 @@
+fun <caret>f1(i1: Int, vararg i: Int){}

idea/testData/quickfix/changeSignature/removeParameterFromExtension.kt

@@ -0,0 +1,4 @@
+// "Remove parameter 'a'" "true"
+
+fun String.foo(<caret>a:Int = 0, b: Int) {
+}

idea/testData/quickfix/changeSignature/removeParameterFromExtension.kt.after

@@ -0,0 +1,4 @@
+// "Remove parameter 'a'" "true"
+
+fun String.foo(b: Int) {
+}

idea/tests/org/jetbrains/kotlin/idea/intentions/IntentionTestGenerated.java

@@ -5725,6 +5725,12 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/convertReceiverToParameter/validOverload.kt");
             doTest(fileName);
         }
+
+        @TestMetadata("varargs.kt")
+        public void testVarargs() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/convertReceiverToParameter/varargs.kt");
+            doTest(fileName);
+        }
     }
 
     @TestMetadata("idea/testData/intentions/convertReferenceToLambda")

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixTestGenerated.java

@@ -1172,6 +1172,12 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
             doTest(fileName);
         }
 
+        @TestMetadata("removeParameterFromExtension.kt")
+        public void testRemoveParameterFromExtension() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/quickfix/changeSignature/removeParameterFromExtension.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("removeParameterFromFakeOverride.kt")
         public void testRemoveParameterFromFakeOverride() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/quickfix/changeSignature/removeParameterFromFakeOverride.kt");