If then to elvis: now not applicable for is with type unrelated to original #KT-14520 Fixed

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

@@ -32,6 +32,7 @@ import org.jetbrains.kotlin.resolve.calls.callUtil.getType
 import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode.Companion.PARTIAL
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.typeUtil.TypeNullability
+import org.jetbrains.kotlin.types.typeUtil.isSubtypeOf
 import org.jetbrains.kotlin.types.typeUtil.nullability
 
 class IfThenToElvisInspection : IntentionBasedInspection<KtIfExpression>(IfThenToElvisIntention::class)
@@ -69,7 +70,10 @@ class IfThenToElvisIntention : SelfTargetingOffsetIndependentIntention<KtIfExpre
                 else -> false
             }
             is KtIsExpression -> {
-                if (!context[BindingContext.TYPE, condition.typeReference].isNotNull()) return false
+                val targetType = context[BindingContext.TYPE, condition.typeReference] ?: return false
+                if (!targetType.isNotNull()) return false
+                val originalType = condition.leftHandSide.getType(context) ?: return false
+                if (!targetType.isSubtypeOf(originalType)) return false
 
                 when (condition.isNegated) {
                     true -> checkedExpression.clausesReplaceableByElvis(thenClause, elseClause, context)

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

@@ -0,0 +1,12 @@
+// IS_APPLICABLE: false
+
+interface A
+interface B
+
+fun prepare(x: A) = x
+fun use(x: A) {}
+
+fun test(x: A) {
+    val xx = <caret>if (x is B) x else prepare(x)
+    use(xx)
+}

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

@@ -1308,6 +1308,12 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("isCheckForUnrelatedType.kt")
+            public void testIsCheckForUnrelatedType() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/branched/ifThenToElvis/isCheckForUnrelatedType.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("isCheckWithSelector.kt")
             public void testIsCheckWithSelector() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/branched/ifThenToElvis/isCheckWithSelector.kt");