Fix "Replace !! with if-then" inspection in receiver position

#KT-5412 Fixed

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

@@ -28,18 +28,15 @@ import com.intellij.psi.PsiDocumentManager
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.idea.intentions.ChooseStringExpression
 import org.jetbrains.kotlin.idea.intentions.SelfTargetingRangeIntention
-import org.jetbrains.kotlin.idea.intentions.branchedTransformations.convertToIfNotNullExpression
-import org.jetbrains.kotlin.idea.intentions.branchedTransformations.convertToIfNullExpression
-import org.jetbrains.kotlin.idea.intentions.branchedTransformations.introduceValueForCondition
-import org.jetbrains.kotlin.idea.intentions.branchedTransformations.isStableSimpleExpression
+import org.jetbrains.kotlin.idea.intentions.branchedTransformations.*
 import org.jetbrains.kotlin.lexer.KtTokens
-import org.jetbrains.kotlin.psi.KtPostfixExpression
-import org.jetbrains.kotlin.psi.KtPsiFactory
-import org.jetbrains.kotlin.psi.KtPsiUtil
-import org.jetbrains.kotlin.psi.KtThrowExpression
+import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.psi.psiUtil.getQualifiedExpressionForReceiver
 import org.jetbrains.kotlin.resolve.bindingContextUtil.isUsedAsStatement
 
-class DoubleBangToIfThenIntention : SelfTargetingRangeIntention<KtPostfixExpression>(KtPostfixExpression::class.java, "Replace '!!' expression with 'if' expression"), LowPriorityAction {
+class DoubleBangToIfThenIntention :
+    SelfTargetingRangeIntention<KtPostfixExpression>(KtPostfixExpression::class.java, "Replace '!!' expression with 'if' expression"),
+    LowPriorityAction {
     override fun applicabilityRange(element: KtPostfixExpression): TextRange? {
         return if (element.operationToken == KtTokens.EXCLEXCL && element.baseExpression != null)
             element.operationReference.textRange
@@ -60,12 +57,31 @@ class DoubleBangToIfThenIntention : SelfTargetingRangeIntention<KtPostfixExpress
 
         val ifStatement = if (isStatement)
             element.convertToIfNullExpression(base, defaultException)
-        else
-            element.convertToIfNotNullExpression(base, base, defaultException)
+        else {
+            val selectorExpression = element.getQualifiedExpressionForReceiver()?.selectorExpression
+            val thenClause = selectorExpression?.let {
+                KtPsiFactory(element).createExpressionByPattern("$0.$1", base, it)
+            } ?: base
+            val hasSelector = thenClause != base
+
+            if (hasSelector) {
+                val prevSibling = selectorExpression?.prevSibling
+                selectorExpression?.delete()
+                prevSibling?.delete()
+            }
+
+            element.convertToIfNotNullExpression(base, thenClause, defaultException).apply {
+                if (hasSelector) {
+                    with(parent) {
+                        firstChild.delete()
+                        lastChild.delete()
+                    }
+                }
+            }
+        }
 
         val thrownExpression =
-                ((if (isStatement) ifStatement.then else ifStatement.`else`) as KtThrowExpression).thrownExpression!!
-
+            ((if (isStatement) ifStatement.then else ifStatement.`else`) as KtThrowExpression).thrownExpression!!
         val message = StringUtil.escapeStringCharacters("Expression '$expressionText' must not be null")
         val nullPtrExceptionText = "NullPointerException(\"$message\")"
         val kotlinNullPtrExceptionText = "KotlinNullPointerException()"
@@ -79,7 +95,7 @@ class DoubleBangToIfThenIntention : SelfTargetingRangeIntention<KtPostfixExpress
         PsiDocumentManager.getInstance(project).doPostponedOperationsAndUnblockDocument(editor.document)
         editor.caretModel.moveToOffset(thrownExpression.node!!.startOffset)
 
-        TemplateManager.getInstance(project).startTemplate(editor, builder.buildInlineTemplate(), object: TemplateEditingAdapter() {
+        TemplateManager.getInstance(project).startTemplate(editor, builder.buildInlineTemplate(), object : TemplateEditingAdapter() {
             override fun templateFinished(template: Template, brokenOff: Boolean) {
                 if (!isStable && !isStatement) {
                     ifStatement.introduceValueForCondition(ifStatement.then!!, editor)

idea/testData/intentions/branched/doubleBangToIfThen/replaceParentExpression.kt

@@ -0,0 +1,15 @@
+// WITH_RUNTIME
+fun foo(): String? {
+    return "foo"
+}
+
+class A {
+    fun f(): Int {
+        return 42
+    }
+}
+
+fun main(args: Array<String>) {
+    val a: A? = A()
+    a<caret>!!.f()
+}

idea/testData/intentions/branched/doubleBangToIfThen/replaceParentExpression.kt.after

@@ -0,0 +1,15 @@
+// WITH_RUNTIME
+fun foo(): String? {
+    return "foo"
+}
+
+class A {
+    fun f(): Int {
+        return 42
+    }
+}
+
+fun main(args: Array<String>) {
+    val a: A? = A()
+    if (a != null) a.f() else throw NullPointerException("Expression 'a' must not be null")
+}

idea/testData/intentions/branched/doubleBangToIfThen/replaceParentExpression2.kt

@@ -0,0 +1,16 @@
+// WITH_RUNTIME
+fun foo(): String? {
+    return "foo"
+}
+
+class A {
+    val g = 44
+    fun f(): Int {
+        return 42
+    }
+}
+
+fun main(args: Array<String>) {
+    val a: A? = A()
+    a<caret>!!.g
+}

idea/testData/intentions/branched/doubleBangToIfThen/replaceParentExpression2.kt.after

@@ -0,0 +1,16 @@
+// WITH_RUNTIME
+fun foo(): String? {
+    return "foo"
+}
+
+class A {
+    val g = 44
+    fun f(): Int {
+        return 42
+    }
+}
+
+fun main(args: Array<String>) {
+    val a: A? = A()
+    if (a != null) a.g else throw NullPointerException("Expression 'a' must not be null")
+}

idea/testData/intentions/branched/doubleBangToIfThen/replaceParentExpression3.kt

@@ -0,0 +1,15 @@
+// WITH_RUNTIME
+fun foo(): String? {
+    return "foo"
+}
+
+class A {
+    fun f(): Int {
+        return 42
+    }
+}
+
+fun main(args: Array<String>) {
+    val a: A? = A()
+    val b = a<caret>!!.f()
+}

idea/testData/intentions/branched/doubleBangToIfThen/replaceParentExpression3.kt.after

@@ -0,0 +1,15 @@
+// WITH_RUNTIME
+fun foo(): String? {
+    return "foo"
+}
+
+class A {
+    fun f(): Int {
+        return 42
+    }
+}
+
+fun main(args: Array<String>) {
+    val a: A? = A()
+    val b = if (a != null) a.f() else throw NullPointerException("Expression 'a' must not be null")
+}

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

@@ -2059,6 +2059,21 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
                 runTest("idea/testData/intentions/branched/doubleBangToIfThen/localVar.kt");
             }
 
+            @TestMetadata("replaceParentExpression.kt")
+            public void testReplaceParentExpression() throws Exception {
+                runTest("idea/testData/intentions/branched/doubleBangToIfThen/replaceParentExpression.kt");
+            }
+
+            @TestMetadata("replaceParentExpression2.kt")
+            public void testReplaceParentExpression2() throws Exception {
+                runTest("idea/testData/intentions/branched/doubleBangToIfThen/replaceParentExpression2.kt");
+            }
+
+            @TestMetadata("replaceParentExpression3.kt")
+            public void testReplaceParentExpression3() throws Exception {
+                runTest("idea/testData/intentions/branched/doubleBangToIfThen/replaceParentExpression3.kt");
+            }
+
             @TestMetadata("simpleNameExpressionInParens.kt")
             public void testSimpleNameExpressionInParens() throws Exception {
                 runTest("idea/testData/intentions/branched/doubleBangToIfThen/simpleNameExpressionInParens.kt");