Minor. Add more tests

compiler/testData/codegen/box/inlineClasses/interfaceDelegation/kt38337Generic.kt

@@ -0,0 +1,14 @@
+// WITH_STDLIB
+// WORKS_WHEN_VALUE_CLASS
+// LANGUAGE: +ValueClasses, +GenericInlineClassParameter
+
+OPTIONAL_JVM_INLINE_ANNOTATION
+value class Wrapper<T: Int>(val id: T)
+
+class DMap(private val map: Map<Wrapper<Int>, String>) :
+        Map<Wrapper<Int>, String> by map
+
+fun box(): String {
+    val dmap = DMap(mutableMapOf(Wrapper(42) to "OK"))
+    return dmap[Wrapper(42)] ?: "Fail"
+}