Why type alias can't reference to another type alias?

[vabka]

using IntList = System.Collections.Generic.List<int>; // ok
using IntListFactory = System.Func<IntList>; // Cannot resolve symbol 'IntList'

[CyrusNajmabadi]

Because usings aren't in 'scope' for subsequent using statements. This was an explicit decision at the time to keep the lookup rules much simpler for the language.

[yaakov-h]

Only for subsequent using statements in the same scope, though. This works fine:

using IntList = System.Collections.Generic.List<int>;

namespace Foo
{
    using IntListFactory = System.Func<IntList>;
    // ...
}