Rust code shared from the playground

playground.rs

mod db_schema{  // diesel generated schema
    pub mod period {
        pub struct table {}
        pub struct tenant_id {}
    }
    
    pub mod category {
        pub struct table {}
        pub struct id {}
    }
}
//use super::db::PgSqlConn;
struct PgSqlConn {}
use diesel;

#[derive(diesel::Queryable)]
pub struct Period {
    
}
#[derive(diesel::Queryable)]
pub struct Category {
    
}

pub trait HasTenantID {
    type TenantIDColumn;
}

pub trait NoTenantID {

}

impl HasTenantID for db_schema::period::table {
    type TenantIDColumn = db_schema::period::tenant_id;
}

// TODO Can this be auto implemented?
impl NoTenantID for db_schema::category::table {
    
}

pub struct TenantedConnection {
    connection: PgSqlConn,
    tenant_id: u32
}

pub trait RunQueryDsl : diesel::RunQueryDsl<TenantedConnection> {

}

impl<T> RunQueryDsl for T where T: diesel::Table + NoTenantID  {

}

// error - this implementation will conflict with the implementation above
impl<T> RunQueryDsl for T where T: diesel::Table + HasTenantID {
    // TODO This execute method can only be called if the query fragment includes
    // a `.filter(T::TenantIDColumn.eq(Conn.tenant_id))`
    // TODO Is there any way to force this in the type system?
    fn execute(self, conn: &TenantedConnection) -> diesel::QueryResult<usize>
    where
        Self: diesel::methods::ExecuteDsl<TenantedConnection>,    
    {
        //...
    }
}

fn get_periods(conn: &TenantedConnection) -> Vec<Period> {
    // This call should fail to compile - does not filter
    diesel::select(db_schema::period::table)
        .load::<Period>().unwrap();
        
    // This call is okay, it filters on tenant id
    diesel::select(db_schema::period::table)
        .filter(db_schema::period::tenant_id.eq(conn.tenant_id))
        .load::<Period>().unwrap()
}

fn get_categories(conn: &TenantedConnection) -> Vec<Category> {
    // This call is fine, category has no tenant id
    diesel::select(db_schema::category::table)
        .load::<Category>().unwrap()
}