Minor. Add more tests

compiler/testData/codegen/box/inlineClasses/kt48993Generic.kt

@@ -0,0 +1,24 @@
+// TARGET_BACKEND: JVM
+// WITH_STDLIB
+// WORKS_WHEN_VALUE_CLASS
+// LANGUAGE: +ValueClasses, +GenericInlineClassParameter
+// FILE: 1.kt
+
+OPTIONAL_JVM_INLINE_ANNOTATION
+value class C<T: String>(val x: T)
+
+// FILE: 2.kt
+@file:JvmMultifileClass
+@file:JvmName("Multifile")
+
+private var result: String? = null
+
+var String.k: C<String>
+    get() = C(this + result!!)
+    set(value) { result = value.x }
+
+// FILE: 3.kt
+fun box(): String {
+    "".k = C("K")
+    return "O".k.x
+}