If then to elvis: now not applicable for calls with nullable result #KT-14542 Fixed

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

@@ -18,6 +18,7 @@ package org.jetbrains.kotlin.idea.intentions.branchedTransformations.intentions
 
 import com.intellij.openapi.editor.Editor
 import org.jetbrains.kotlin.KtNodeTypes
+import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.idea.core.replaced
 import org.jetbrains.kotlin.idea.inspections.IntentionBasedInspection
 import org.jetbrains.kotlin.idea.intentions.SelfTargetingOffsetIndependentIntention
@@ -26,6 +27,10 @@ import org.jetbrains.kotlin.idea.intentions.getLeftMostReceiverExpression
 import org.jetbrains.kotlin.idea.intentions.replaceFirstReceiver
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.resolve.calls.callUtil.getType
+import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode.Companion.PARTIAL
+import org.jetbrains.kotlin.types.typeUtil.TypeNullability
+import org.jetbrains.kotlin.types.typeUtil.nullability
 
 class IfThenToElvisInspection : IntentionBasedInspection<KtIfExpression>(IfThenToElvisIntention::class)
 
@@ -36,7 +41,7 @@ class IfThenToElvisIntention : SelfTargetingOffsetIndependentIntention<KtIfExpre
 
     private fun KtExpression.clausesReplaceableByElvis(firstClause: KtExpression, secondClause: KtExpression) =
             !firstClause.isNullOrBlockExpression() &&
-            (secondClause.evaluatesTo(this) || secondClause.hasFirstReceiverOf(this)) &&
+            (secondClause.evaluatesTo(this) || secondClause.hasFirstReceiverOf(this) && !secondClause.isNullableExpression()) &&
             !(firstClause is KtThrowExpression && firstClause.throwsNullPointerExceptionWithNoArguments())
 
     private fun KtExpression.checkedExpression() = when (this) {
@@ -72,6 +77,8 @@ class IfThenToElvisIntention : SelfTargetingOffsetIndependentIntention<KtIfExpre
         return innerExpression is KtBlockExpression || innerExpression.node.elementType == KtNodeTypes.NULL
     }
 
+    private fun KtExpression.isNullableExpression() = getType(analyze(PARTIAL))?.nullability() != TypeNullability.NOT_NULL
+
     private fun KtExpression.hasFirstReceiverOf(receiver: KtExpression): Boolean {
         val actualReceiver = (unwrapBlockOrParenthesis() as? KtDotQualifiedExpression)?.getLeftMostReceiverExpression() ?: return false
         return actualReceiver.evaluatesTo(receiver)

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

@@ -0,0 +1,7 @@
+// IS_APPLICABLE: false
+
+fun foo(p: String?): String? {
+    return <caret>if (p != null) p.bar() else "a"
+}
+
+fun String.bar(): String? = null

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

@@ -1404,6 +1404,12 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("nullableThen.kt")
+            public void testNullableThen() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/branched/ifThenToElvis/nullableThen.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("otherBlockHasMoreThanOneStatement.kt")
             public void testOtherBlockHasMoreThanOneStatement() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/branched/ifThenToElvis/otherBlockHasMoreThanOneStatement.kt");