private void MapAliases(Expression a, Expression b)
{
var gatherer = new DeclaredAliasGatherer();
Alias[] prodA = gatherer.Gather(a).ToArray();
Alias[] prodB = gatherer.Gather(b).ToArray();
for (int i = 0, n = prodA.Length; i < n; i++)
{
_aliasScope.Add(prodA[i], prodB[i]);
}
}
