Handle union properties completions on apparant types

Author: mhegazy

src/compiler/checker.ts

@@ -7916,7 +7916,7 @@ module ts {
                 var symbols: Symbol[] = [];
                 var name = symbol.name;
                 forEach(getSymbolLinks(symbol).unionType.types, t => {
-                    symbols.push(getPropertyOfType(t, name));
+                    symbols.push(getPropertyOfType(getApparentType(t), name));
                 });
                 return symbols;
             }

tests/cases/fourslash/completionEntryForUnionProperty2.ts

@@ -0,0 +1,19 @@
+///<reference path="fourslash.ts" />
+
+////interface One {
+////    commonProperty: number;
+////    commonFunction(): number;
+////}
+////
+////interface Two {
+////    commonProperty: string
+////    commonFunction(): number;
+////}
+////
+////var x : One | Two;
+////
+////x.commonProperty./**/
+
+goTo.marker();
+verify.memberListContains("toString", "() => string", undefined, undefined, "method");
+verify.memberListCount(1);