Why is `DefaultBufFactory` private? (prevents generic use of `quiche::Connection<F>`)

[birneee]

I have a question about the visibility of DefaultBufFactory and whether this is an intentional design choice.

I would like to create a generic data structure around quiche::Connection so that it can work with either a custom BufFactory or the default one. For example:

struct ConnectionMap<F: BufFactory>(HashMap<usize, Connection<F>>);

This works fine with a custom implementation:

ConnectionMap::<MyCustomBufFactory>::new();

However, because DefaultBufFactory is private, I can’t instantiate the same structure using the default buffer factory:

ConnectionMap::<DefaultBufFactory>::new(); // not possible

As a workaround, I can define two separate types:

struct ConnectionMapWithBufFactory<F: BufFactory>(HashMap<usize, Connection<F>>);
struct ConnectionMapWithoutBufFactory(HashMap<usize, Connection>);

But this quickly propagates to other structs and forces duplication or additional abstraction such as:

trait ConnectionMapWithOrWithoutBufFactory {}
impl ConnectionMapWithOrWithoutBufFactory for ConnectionMapWithBufFactory {}
impl ConnectionMapWithOrWithoutBufFactory for ConnectionMapWithoutBufFactory {}

struct Endpoint<M: ConnectionMapWithOrWithoutBufFactory> { ... }

Should DefaultBufFactory be public?