Obsolete KT-1776: Can't resolve members of auto-casted "this" in extension without typing "this" explicitly

#KT-1776 Obsolete

compiler/testData/codegen/box/extensionFunctions/kt1776.kt

@@ -0,0 +1,20 @@
+trait Expr {
+    public fun ttFun() : Int = 12
+}
+
+class Num(val value : Int) : Expr
+
+fun Expr.sometest() : Int {
+    if (this is Num) {
+        value
+        return value
+    }
+    return 0;
+}
+
+
+fun box() : String {
+    if (Num(11).sometest() != 11) return "fail ${Num(11).sometest()}"
+
+    return "OK"
+}

compiler/tests/org/jetbrains/jet/codegen/generated/BlackBoxCodegenTestGenerated.java

@@ -2771,6 +2771,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest(fileName);
         }
         
+        @TestMetadata("kt1776.kt")
+        public void testKt1776() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/box/extensionFunctions/kt1776.kt");
+            doTest(fileName);
+        }
+        
         @TestMetadata("kt1953.kt")
         public void testKt1953() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/box/extensionFunctions/kt1953.kt");