Supported generic subclasses in submethods.

#KT-2776 in progress

compiler/testData/loadJava/kotlinSignature/propagation/return/InheritNullabilityGenericSubclassSimple.java

@@ -0,0 +1,20 @@
+package test;
+
+import org.jetbrains.annotations.NotNull;
+import java.util.List;
+import java.util.Collection;
+
+import jet.runtime.typeinfo.KotlinSignature;
+
+public class InheritNullabilityGenericSubclassSimple {
+    @KotlinSignature("fun foo(): MutableCollection<String>")
+    public Collection<String> foo() {
+        throw new UnsupportedOperationException();
+    }
+
+    public class Sub extends InheritNullabilityGenericSubclassSimple {
+        public List<String> foo() {
+            throw new UnsupportedOperationException();
+        }
+    }
+}

compiler/testData/loadJava/kotlinSignature/propagation/return/InheritNullabilityGenericSubclassSimple.kt

@@ -0,0 +1,11 @@
+package test
+
+import org.jetbrains.annotations.NotNull
+
+public open class InheritNullabilityGenericSubclassSimple : java.lang.Object() {
+    public open fun foo(): MutableCollection<String> = throw UnsupportedOperationException()
+
+    public open class Sub: InheritNullabilityGenericSubclassSimple() {
+        override fun foo(): MutableList<String> = throw UnsupportedOperationException()
+    }
+}

compiler/testData/loadJava/kotlinSignature/propagation/return/InheritNullabilityGenericSubclassSimple.txt

@@ -0,0 +1,10 @@
+namespace test
+
+public open class test.InheritNullabilityGenericSubclassSimple : java.lang.Object {
+    public final /*constructor*/ fun <init>(): test.InheritNullabilityGenericSubclassSimple
+    public open fun foo(): jet.MutableCollection<jet.String>
+    public open class test.InheritNullabilityGenericSubclassSimple.Sub : test.InheritNullabilityGenericSubclassSimple {
+        public final /*constructor*/ fun <init>(): test.InheritNullabilityGenericSubclassSimple.Sub
+        public open override /*1*/ fun foo(): jet.MutableList<jet.String>
+    }
+}