Kotlin !is does not work well with RemoveRedundantNullCheckBeforeInstanceof

Author: timtebeek

src/main/java/org/openrewrite/staticanalysis/RemoveRedundantNullCheckBeforeInstanceof.java

@@ -18,12 +18,14 @@
 import lombok.EqualsAndHashCode;
 import lombok.Value;
 import org.openrewrite.ExecutionContext;
+import org.openrewrite.Preconditions;
 import org.openrewrite.Recipe;
 import org.openrewrite.TreeVisitor;
 import org.openrewrite.java.JavaVisitor;
 import org.openrewrite.java.search.SemanticallyEqual;
 import org.openrewrite.java.tree.Expression;
 import org.openrewrite.java.tree.J;
+import org.openrewrite.staticanalysis.kotlin.KotlinFileChecker;
 
 import java.time.Duration;
 import java.util.Collections;
@@ -55,7 +57,7 @@ public Duration getEstimatedEffortPerOccurrence() {
 
     @Override
     public TreeVisitor<?, ExecutionContext> getVisitor() {
-        return new JavaVisitor<ExecutionContext>() {
+        return Preconditions.check(Preconditions.not(new KotlinFileChecker<>()), new JavaVisitor<ExecutionContext>() {
             @Override
             public J visitBinary(J.Binary binary, ExecutionContext ctx) {
                 J.Binary bi = (J.Binary) super.visitBinary(binary, ctx);
@@ -107,6 +109,6 @@ private boolean isRedundantNullCheck(J.Binary nullCheck, J.InstanceOf instanceOf
                 }
                 return false;
             }
-        };
+        });
     }
 }

src/test/java/org/openrewrite/staticanalysis/RemoveRedundantNullCheckBeforeInstanceofTest.java

@@ -17,10 +17,12 @@
 
 import org.junit.jupiter.api.Test;
 import org.openrewrite.DocumentExample;
+import org.openrewrite.Issue;
 import org.openrewrite.test.RecipeSpec;
 import org.openrewrite.test.RewriteTest;
 
 import static org.openrewrite.java.Assertions.java;
+import static org.openrewrite.kotlin.Assertions.kotlin;
 
 @SuppressWarnings({"ConstantConditions", "ConditionCoveredByFurtherCondition"})
 class RemoveRedundantNullCheckBeforeInstanceofTest implements RewriteTest {
@@ -421,4 +423,23 @@ void foo(Object a, Object b) {
           )
         );
     }
+
+    @Issue("https://github.com/openrewrite/rewrite/pull/5736")
+    @Test
+    void kotlinIsNotInstanceOf() {
+        rewriteRun(
+          //language=kotlin
+          kotlin(
+            """
+              class A {
+                fun foo(s: Object?) {
+                  if (s != null && s !is String) {
+                    println("Not null nor String")
+                  }
+                }
+              }
+              """
+          )
+        );
+    }
 }