KT-2109 Nullability inference fails in extension function

#KT-2109 Fixed

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/autocasts/DataFlowValueFactory.java

@@ -52,7 +52,7 @@ public class DataFlowValueFactory {
     @NotNull
     public DataFlowValue createDataFlowValue(@NotNull ThisReceiverDescriptor receiver) {
         JetType type = receiver.getType();
-        return new DataFlowValue(receiver.getDeclarationDescriptor(), type, true, getImmanentNullability(type));
+        return new DataFlowValue(receiver, type, true, getImmanentNullability(type));
     }
 
     @NotNull

compiler/testData/diagnostics/tests/nullabilityAndAutoCasts/kt2109.jet

@@ -0,0 +1,20 @@
+//KT-2109 Nullability inference fails in extension function
+package kt2109
+
+class A {
+    fun foo() {}
+}
+
+fun A?.bar() {
+    if (this == null) {
+        return
+    }
+    foo()
+}
+
+fun A.baz() {
+    if (<!SENSELESS_COMPARISON!>this == null<!>) {
+        return
+    }
+    foo()
+}