protected virtual bool IsEquivalent(SymPointerType other) => false;
 protected override bool IsEquivalent(SymPointerType other) => Alias.IsEquivalent(other);
 protected override bool IsEquivalent(SymPointerType other) =>
 ReferencedSymType.IsEquivalent(other.ReferencedSymType);
 protected override bool IsEquivalent(SymPointerType other) => true;