Reflect Kotlin's declaration-site variance in Java signatures

compiler/testData/writeSignature/declarationSiteVariance/OutOfOutInOutPosition.kt

@@ -0,0 +1,19 @@
+class Out<out T>
+class X
+
+// Why we want this to be translated to 'Out<Out<? extends X>> f()' instead of 'Out<Out<X>> f()'
+// There are two instantiations of 'In' in this test: outer Out<...> and inner Out<X>
+// So why do we want to put a wildcard on the inner one and not the outer?
+// People don't want wildcards in return types, because they are _long_. So we try our best to remove wildcards where possible
+// Not putting a wildcard on the outer occurrence is not imposing a restriction, actually it is removing one:
+//     anything that can be done with Out<? extends X> in Java can be done with Out<X>
+// But omitting the wildcard on the inner occurrence is restrictive:
+//     one can add a List<String> to a List<List<? extends CharSequence>>,
+//     but not to a List<List<CharSequence>>,
+//     thus removing the wildcard would be restricting the use of the return value of the method, and we don't want do this.
+fun f(): Out<Out<X>> = throw Exception()
+
+// method: namespace::f
+// jvm signature:     ()LOut;
+// generic signature: ()LOut<LOut<+LX;>;>;
+// kotlin signature:  ()LOut<LOut<LX;>;>;