"Convert lambda to reference": fix false positive for vararg function

#KT-16422 Fixed

idea/src/org/jetbrains/kotlin/idea/intentions/ConvertLambdaToReferenceIntention.kt

@@ -36,6 +36,7 @@ import org.jetbrains.kotlin.resolve.BindingContext.FUNCTION
 import org.jetbrains.kotlin.resolve.BindingContext.REFERENCE_TARGET
 import org.jetbrains.kotlin.resolve.calls.callUtil.getResolvedCall
 import org.jetbrains.kotlin.resolve.calls.components.hasDefaultValue
+import org.jetbrains.kotlin.resolve.calls.model.VarargValueArgument
 import org.jetbrains.kotlin.resolve.descriptorUtil.isCompanionObject
 import org.jetbrains.kotlin.resolve.scopes.receivers.ExtensionReceiver
 import org.jetbrains.kotlin.resolve.scopes.utils.getImplicitReceiversHierarchy
@@ -128,8 +129,9 @@ open class ConvertLambdaToReferenceIntention(text: String) :
             if (lambdaValueParameterDescriptors.size < explicitReceiverShift + callableExpression.valueArguments.size) return false
             val resolvedCall = callableExpression.getResolvedCall(context) ?: return false
             resolvedCall.valueArguments.entries.forEach { (valueParameter, resolvedArgument) ->
-                val argumentExpression =
+                val argument = resolvedArgument.arguments.singleOrNull() ?: return false
-                    resolvedArgument.arguments.singleOrNull()?.getArgumentExpression() as? KtNameReferenceExpression ?: return false
+                if (resolvedArgument is VarargValueArgument && argument.getSpreadElement() == null) return false
+                val argumentExpression = argument.getArgumentExpression() as? KtNameReferenceExpression ?: return false
                 val argumentTarget = context[REFERENCE_TARGET, argumentExpression] as? ValueParameterDescriptor ?: return false
                 if (argumentTarget != lambdaValueParameterDescriptors[valueParameter.index + explicitReceiverShift]) return false
             }

idea/testData/intentions/convertLambdaToReference/varargFunction.kt

@@ -0,0 +1,5 @@
+// IS_APPLICABLE: false
+// WITH_RUNTIME
+fun test(i: Int?): IntArray? {
+    return i?.let { <caret>intArrayOf(it) }
+}

idea/testData/intentions/convertLambdaToReference/varargFunction2.kt

@@ -0,0 +1,6 @@
+// WITH_RUNTIME
+fun test(vararg i: Int): IntArray {
+    return i.let { <caret>double(*it) }
+}
+
+fun double(vararg elements: Int): IntArray = elements.map { it * 2 }.toIntArray()

idea/testData/intentions/convertLambdaToReference/varargFunction2.kt.after

@@ -0,0 +1,6 @@
+// WITH_RUNTIME
+fun test(vararg i: Int): IntArray {
+    return i.let(::double)
+}
+
+fun double(vararg elements: Int): IntArray = elements.map { it * 2 }.toIntArray()

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

@@ -5400,6 +5400,16 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             runTest("idea/testData/intentions/convertLambdaToReference/unwrap.kt");
         }
 
+        @TestMetadata("varargFunction.kt")
+        public void testVarargFunction() throws Exception {
+            runTest("idea/testData/intentions/convertLambdaToReference/varargFunction.kt");
+        }
+
+        @TestMetadata("varargFunction2.kt")
+        public void testVarargFunction2() throws Exception {
+            runTest("idea/testData/intentions/convertLambdaToReference/varargFunction2.kt");
+        }
+
         @TestMetadata("wrongNamedOrder.kt")
         public void testWrongNamedOrder() throws Exception {
             runTest("idea/testData/intentions/convertLambdaToReference/wrongNamedOrder.kt");