Minor. Add more tests

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

@@ -0,0 +1,14 @@
+// WITH_STDLIB
+// WORKS_WHEN_VALUE_CLASS
+// LANGUAGE: +ValueClasses, +GenericInlineClassParameter
+
+OPTIONAL_JVM_INLINE_ANNOTATION
+value class IC<T: String>(val x: T) {
+    private fun privateFun() = x
+    override fun toString() = privateFun()
+}
+
+fun box(): String {
+    val x: Any = IC("OK")
+    return x.toString()
+}