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;