C++: Fix lookup for instantiation of using

Yet another std::vector issue...

Use-cases:
// Case 1
template<typename T>
using type = T;

// Case 2
struct Parent {
    template<typename T>
    using type = T;
};

// Case 3
template<typename T>
struct ParentT {
    template<typename DT>
    using type = DT;
};

struct Foo { int bar; };

void func()
{
    type<Foo> p1;
    Parent::type<Foo> p2;
    ParentT<Foo>::type<Foo> p3;
    // bar not highlighted
    p1.bar;
    p2.bar;
    p3.bar;
}

Task-number: QTCREATORBUG-14480
Change-Id: I9ab08ea7360a432c48eb4b85aa0d63e08d2464c1
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>

src/libs/cplusplus/TypeResolver.cpp

@@ -210,6 +210,10 @@ bool TypeResolver::findTypedef(const QList<LookupItem> &namedTypeItems, FullySpe
 {
     foreach (const LookupItem &it, namedTypeItems) {
         Symbol *declaration = it.declaration();
+        if (!declaration)
+            continue;
+        if (Template *specialization = declaration->asTemplate())
+            declaration = specialization->declaration();
         if (!declaration || (!declaration->isTypedef() && !declaration->type().isDecltype()))
             continue;
         if (visited.contains(declaration))
@@ -237,7 +241,7 @@ bool TypeResolver::findTypedef(const QList<LookupItem> &namedTypeItems, FullySpe
                 return true;
             }
         } else {
-            *type = declaration->type();
+            *type = it.type();
         }
 
         *scope = it.scope();