Make `sqlx::Type` object safe by taking `&self`

[tqwewe]

The trait sqlx::Type is not object safe, as it does not take &self in it's two methods fn type_info() -> TypeInfo and fn compatible(ty: TypeInfo) -> bool.

This is a major issue in a project I'm working on (sea-query & sea-orm), as in my case I am passing values as dyn Trait objects, but cannot include sqlx::Type in the trait objects.

For example, my trait has:

trait QueryValue: sqlx::Encode<'static, sqlx::MySql> + sqlx::Type<sqlx::MySql> {
    fn query_value(&self, query_builder: &dyn QueryBuilder) -> String;
}

But this does not work as sqlx::Type cannot be made into a trait object.

Another example would be if you had an enum containing many database types:

enum Value {
    Bool(Option<bool>),
    TinyInt(Option<i8>),
    SmallInt(Option<i16>),
    String(Option<Box<String>>),
    ...
    Custom(Box<dyn QueryValue>),
}

This cannot be done without adding a generic to the Value enum, which in my case needs to be avoided.

Is there any kind of workaround possible for this situation? My main use for QueryValue is to pass it to .bind(value) for use in queries.

[ikrivosheev]

Hello! Any updates?)

[abonander]

The Type trait is not intended to be object-safe. I suggest working around it another way.