Using aliases sorting is not always the same depending on the input order

[araxor]

Input 1:

using A = string;
using B = string;
using C = string;
using D = string;

Output 1:

using D = string;
using C = string;
using B = string;
using A = string;

Input 2:

using D = string;
using C = string;
using B = string;
using A = string;

Output 2:

using A = string;
using B = string;
using C = string;
using D = string;

Input 3:

using C = string;
using D = string;
using B = string;
using A = string;

Output 3:

using A = string;
using B = string;
using D = string;
using C = string;

Expected behavior:
All inputs should have the same output (output 2 in the examples above).