JVM_IR KT-43242 generate switch subject as primitive 'int'

compiler/testData/codegen/box/when/kt43242.kt

@@ -0,0 +1,28 @@
+// TARGET_BACKEND: JVM
+// FILE: kt43242.kt
+
+fun fromJson() {
+    test = Bar().fromJson()?.let {
+        when (it) {
+            0 -> false
+            1 -> true
+            else -> true
+        }
+    }
+}
+
+var test: Any? = "xxx"
+
+fun box(): String {
+    fromJson()
+    return if (test != null) "Fail: $test" else "OK"
+}
+
+// FILE: Bar.java
+import org.jetbrains.annotations.Nullable;
+
+public class Bar {
+    public final @Nullable Integer fromJson() {
+        return null;
+    }
+}