Fix replacedBaseClause for selector which has implicit receiver

#KT-19666 Fixed

idea/src/org/jetbrains/kotlin/idea/intentions/branchedTransformations/IfThenUtils.kt

@@ -165,13 +165,20 @@ data class IfThenToSelectData(
                                               it.leftHandSide,
                                               it.typeReference!!)
         }
+
         return if (baseClauseEvaluatesToReceiver()) {
             if (condition is KtIsExpression) newReceiver!! else baseClause
         }
         else {
             when {
-                condition is KtIsExpression -> (baseClause as KtDotQualifiedExpression).replaceFirstReceiver(
-                        factory, newReceiver!!, safeAccess = true)
+                condition is KtIsExpression -> {
+                    when {
+                        baseClause is KtDotQualifiedExpression -> baseClause.replaceFirstReceiver(
+                                factory, newReceiver!!, safeAccess = true)
+                        hasImplicitReceiver() -> factory.createExpressionByPattern("$0?.$1", newReceiver!!, baseClause).insertSafeCalls(factory)
+                        else -> error("Illegal state")
+                    }
+                }
                 hasImplicitReceiver() -> factory.createExpressionByPattern("this?.$0", baseClause).insertSafeCalls(factory)
                 else -> baseClause.insertSafeCalls(factory)
             }

idea/testData/intentions/branched/ifThenToElvis/kt19666.kt

@@ -0,0 +1,13 @@
+// WITH_RUNTIME
+interface Taggable {
+    val tag: String
+}
+
+fun Any.log() {
+    val tag = <caret>if (this is Taggable) {
+        tag
+    }
+    else {
+        this::class.java.simpleName
+    }
+}

idea/testData/intentions/branched/ifThenToElvis/kt19666.kt.after

@@ -0,0 +1,8 @@
+// WITH_RUNTIME
+interface Taggable {
+    val tag: String
+}
+
+fun Any.log() {
+    val tag = (this as? Taggable)?.tag ?: this::class.java.simpleName
+}

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

@@ -1423,6 +1423,12 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("kt19666.kt")
+            public void testKt19666() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/branched/ifThenToElvis/kt19666.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("lhsEqualsNull.kt")
             public void testLhsEqualsNull() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/branched/ifThenToElvis/lhsEqualsNull.kt");