[Test] Reproduce KT-58823

compiler/testData/codegen/box/smartCasts/smartcastOnImplicitDispatchReceiver.kt

@@ -0,0 +1,23 @@
+// TARGET_BACKEND: JVM
+// IGNORE_BACKEND_K2: JVM_IR
+// ISSUE: KT-58823
+// FILE: Base.java
+
+public abstract class Base {}
+
+// FILE: Derived.java
+public class Derived extends Base {
+    <T> T getResult() {
+        return (T) "OK";
+    }
+}
+
+// FILE: main.kt
+fun Base.box(): String {
+    return when (this) {
+        is Derived -> getResult()
+        else -> "Fail"
+    }
+}
+
+fun box(): String = Derived().box()