KT-14032 related: if expression to elvis now handles also is and !is checks

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

@@ -27,26 +27,38 @@ import org.jetbrains.kotlin.psi.*
 
 class IfThenToElvisInspection : IntentionBasedInspection<KtIfExpression>(IfThenToElvisIntention::class)
 
-class IfThenToElvisIntention : SelfTargetingOffsetIndependentIntention<KtIfExpression>(KtIfExpression::class.java, "Replace 'if' expression with elvis expression") {
+class IfThenToElvisIntention : SelfTargetingOffsetIndependentIntention<KtIfExpression>(
+        KtIfExpression::class.java,
+        "Replace 'if' expression with elvis expression"
+) {
+
+    private fun KtExpression.clausesReplaceableByElvis(firstClause: KtExpression, secondClause: KtExpression) =
+            firstClause.isNotNullExpression() && secondClause.evaluatesTo(this) &&
+            !(firstClause is KtThrowExpression && firstClause.throwsNullPointerExceptionWithNoArguments())
 
     override fun isApplicableTo(element: KtIfExpression): Boolean {
-        val condition = element.condition as? KtBinaryExpression ?: return false
+        val condition = element.condition as? KtOperationExpression ?: return false
         val thenClause = element.then ?: return false
         val elseClause = element.`else` ?: return false
 
-        val expression = condition.expressionComparedToNull() ?: return false
+        val expression = when (condition) {
+            is KtBinaryExpression -> condition.expressionComparedToNull() ?: return false
+            is KtIsExpression -> condition.leftHandSide
+            else -> return false
+
+        }
         if (!expression.isStableVariable()) return false
 
-        return when (condition.operationToken) {
-            KtTokens.EQEQ ->
-                thenClause.isNotNullExpression() && elseClause.evaluatesTo(expression) &&
-                !(thenClause is KtThrowExpression && thenClause.throwsNullPointerExceptionWithNoArguments())
-
-
-            KtTokens.EXCLEQ ->
-                elseClause.isNotNullExpression() && thenClause.evaluatesTo(expression) &&
-                !(elseClause is KtThrowExpression && elseClause.throwsNullPointerExceptionWithNoArguments())
-
+        return when (condition) {
+            is KtBinaryExpression -> when (condition.operationToken) {
+                KtTokens.EQEQ -> expression.clausesReplaceableByElvis(thenClause, elseClause)
+                KtTokens.EXCLEQ -> expression.clausesReplaceableByElvis(elseClause, thenClause)
+                else -> false
+            }
+            is KtIsExpression -> when (condition.isNegated) {
+                true -> expression.clausesReplaceableByElvis(thenClause, elseClause)
+                false -> expression.clausesReplaceableByElvis(elseClause, thenClause)
+            }
             else -> false
         }
     }
@@ -57,22 +69,32 @@ class IfThenToElvisIntention : SelfTargetingOffsetIndependentIntention<KtIfExpre
     }
 
     override fun applyTo(element: KtIfExpression, editor: Editor?) {
-        val condition = element.condition as KtBinaryExpression
+        val condition = element.condition as KtOperationExpression
 
         val thenClause = element.then!!
         val elseClause = element.`else`!!
         val thenExpression = thenClause.unwrapBlockOrParenthesis()
         val elseExpression = elseClause.unwrapBlockOrParenthesis()
 
-        val (left, right) =
-                when(condition.operationToken) {
-                    KtTokens.EQEQ -> Pair(elseExpression, thenExpression)
-                    KtTokens.EXCLEQ -> Pair(thenExpression, elseExpression)
-                    else -> throw IllegalArgumentException()
-                }
+        val (left, right) = when (condition) {
+            is KtBinaryExpression -> when (condition.operationToken) {
+                KtTokens.EQEQ -> Pair(elseExpression, thenExpression)
+                KtTokens.EXCLEQ -> Pair(thenExpression, elseExpression)
+                else -> throw IllegalArgumentException()
+            }
+            is KtIsExpression -> when (condition.isNegated) {
+                true -> Pair(elseExpression, thenExpression)
+                false -> Pair(thenExpression, elseExpression)
+            }
+            else -> throw IllegalArgumentException()
+        }
 
-        val newExpr = element.replaced(KtPsiFactory(element).createExpressionByPattern("$0 ?: $1", left, right))
-        val elvis = KtPsiUtil.deparenthesize(newExpr) as KtBinaryExpression
+        val factory = KtPsiFactory(element)
+        val newExpr = factory.createExpressionByPattern("$0 ?: $1", left, right) as KtBinaryExpression
+        if (condition is KtIsExpression) {
+            newExpr.left!!.replace(factory.createExpressionByPattern("$0 as? $1", left, condition.typeReference!!))
+        }
+        val elvis = KtPsiUtil.deparenthesize(element.replaced(newExpr)) as KtBinaryExpression
 
         if (editor != null) {
             elvis.inlineLeftSideIfApplicableWithPrompt(editor)

idea/testData/intentions/branched/ifThenToElvis/inspectionData/expected.xml

@@ -103,4 +103,20 @@
     <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">If-Then foldable to '?:'</problem_class>
     <description>Replace 'if' expression with elvis expression</description>
   </problem>
+  <problem>
+    <file>notIsCheck.kt</file>
+    <line>4</line>
+    <module>light_idea_test_case</module>
+    <entry_point TYPE="file" FQNAME="temp:///src/notIsCheck.kt" />
+    <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">If-Then foldable to '?:'</problem_class>
+    <description>Replace 'if' expression with elvis expression</description>
+  </problem>
+  <problem>
+    <file>isCheck.kt</file>
+    <line>4</line>
+    <module>light_idea_test_case</module>
+    <entry_point TYPE="file" FQNAME="temp:///src/isCheck.kt" />
+    <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">If-Then foldable to '?:'</problem_class>
+    <description>Replace 'if' expression with elvis expression</description>
+  </problem>
 </problems>

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

@@ -0,0 +1,5 @@
+class My(val x: Int)
+
+fun foo(arg: Any?): My {
+    return if (<caret>arg is My) arg else My(42)
+}

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

@@ -0,0 +1,5 @@
+class My(val x: Int)
+
+fun foo(arg: Any?): My {
+    return arg as? My ?: My(42)
+}

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

@@ -0,0 +1,5 @@
+class My(val x: Int)
+
+fun foo(arg: Any?): My {
+    return if (<caret>arg !is My) My(42) else arg
+}

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

@@ -0,0 +1,5 @@
+class My(val x: Int)
+
+fun foo(arg: Any?): My {
+    return arg as? My ?: My(42)
+}

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

@@ -1296,6 +1296,12 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("isCheck.kt")
+            public void testIsCheck() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/branched/ifThenToElvis/isCheck.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("lhsEqualsNull.kt")
             public void testLhsEqualsNull() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/branched/ifThenToElvis/lhsEqualsNull.kt");
@@ -1356,6 +1362,12 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("notIsCheck.kt")
+            public void testNotIsCheck() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/branched/ifThenToElvis/notIsCheck.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("nullBranchAlsoNull.kt")
             public void testNullBranchAlsoNull() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/branched/ifThenToElvis/nullBranchAlsoNull.kt");