[Test] Merge box against java testdata into codegen black box testsdata

compiler/testData/codegen/reflection/mapping/javaFields.kt

@@ -0,0 +1,60 @@
+// DONT_TARGET_EXACT_BACKEND: JS JS_IR JS_IR_ES6 WASM NATIVE
+// WITH_REFLECT
+// FULL_JDK
+// MODULE: lib
+// FILE: J.java
+
+public class J {
+    public final int i;
+    public String s;
+
+    public J(int i, String s) {
+        this.i = i;
+        this.s = s;
+    }
+}
+
+// MODULE: main(lib)
+// FILE: 1.kt
+
+import java.lang.reflect.*
+import kotlin.reflect.*
+import kotlin.reflect.jvm.*
+
+fun box(): String {
+    val i = J::i
+    val s = J::s
+
+    // Check that correct reflection objects are created
+    assert(i !is KMutableProperty<*>) { "Fail i class: ${i.javaClass}" }
+    assert(s is KMutableProperty<*>) { "Fail s class: ${s.javaClass}" }
+
+    // Check that no Method objects are created for such properties
+    assert(i.javaGetter == null) { "Fail i getter" }
+    assert(s.javaGetter == null) { "Fail s getter" }
+    assert(s.javaSetter == null) { "Fail s setter" }
+
+    // Check that correct Field objects are created
+    val ji = i.javaField!!
+    val js = s.javaField!!
+    assert(Modifier.isFinal(ji.getModifiers())) { "Fail i final" }
+    assert(!Modifier.isFinal(js.getModifiers())) { "Fail s final" }
+
+    // Check that those Field objects work as expected
+    val a = J(42, "abc")
+    assert(ji.get(a) == 42) { "Fail ji get" }
+    assert(js.get(a) == "abc") { "Fail js get" }
+    js.set(a, "def")
+    assert(js.get(a) == "def") { "Fail js set" }
+    assert(a.s == "def") { "Fail js access" }
+
+    // Check that valid Kotlin reflection objects are created by those Field objects
+    val ki = ji.kotlinProperty as KProperty1<J, Int>
+    val ks = js.kotlinProperty as KMutableProperty1<J, String>
+    assert(ki.get(a) == 42) { "Fail ki get" }
+    assert(ks.get(a) == "def") { "Fail ks get" }
+    ks.set(a, "ghi")
+    assert(ks.get(a) == "ghi") { "Fail ks set" }
+
+    return "OK"
+}