Generic BoxedQuery for functions?

[durango]

Basically, trying to refactor code a bit for my app and have the following:

use params::Map;
use diesel::prelude::*;
use diesel::pg::Pg;

struct ListData<Table> {
    _marker: PhantomData<Table>
}

impl<ST> ListData<ST> where
    ST: Table
{
    pub fn set_page<'a, T>(params: &Map, max_items: i64, source: &mut T) -> &'a BoxedSelectStatement<'a, <ST as Table>::AllColumns, ST, Pg> where
        T: QuerySource + AsQuery,
        T::Query: InternalBoxedDsl<'a, Pg>
    {
        // match params.find(&["page"]) {
        //     Some(&ParamsValue::String(ref page)) => {
        //         let mut current_page = page.parse::<i64>().unwrap_or(0);
        //         if current_page < 1 {
        //             current_page = 0
        //         }
        //
        //         source = source.offset(current_page * max_items)
        //     },
        //     _ => (),
        // }

        source = source.limit(max_items)
    }
}

let map = itry!(req.get_ref::<Params>());
let mut source = users::table.into_boxed::<Pg>();
source = ListData::<users::table>::set_page(map, 30, &mut source);

And then the error:

error: no method named `limit` found for type `&mut T` in the current scope
  --> src/users/routes.rs:74:25
   |
74 |         source = source.limit(max_items)
   |                         ^^^^^
   |
   = note: the method `limit` exists but the following trait bounds were not satisfied: `&mut T : diesel::QuerySource`, `&mut T : diesel::query_builder::AsQuery`, `_ : diesel::LimitDsl`, `&mut T : diesel::query_builder::Query`, `&&mut T : diesel::QuerySource`, `&&mut T : diesel::query_builder::AsQuery`, `_ : diesel::LimitDsl`, `&&mut T : diesel::query_builder::Query`, `&mut &mut T : diesel::QuerySource`, `&mut &mut T : diesel::query_builder::AsQuery`, `_ : diesel::LimitDsl`, `&mut &mut T : diesel::query_builder::Query`, `<T as diesel::query_builder::AsQuery>::Query : diesel::LimitDsl`, `&T : diesel::QuerySource`, `&T : diesel::query_builder::AsQuery`, `_ : diesel::LimitDsl`, `&T : diesel::query_builder::Query`, `&mut T : diesel::QuerySource`, `&mut T : diesel::query_builder::AsQuery`, `_ : diesel::LimitDsl`, `&mut T : diesel::query_builder::Query`
   = help: items from traits can only be used if the trait is implemented and in scope; the following trait defines an item `limit`, perhaps you need to implement it:
   = help: candidate #1: `diesel::LimitDsl`

error[E0275]: overflow evaluating the requirement `diesel::query_builder::BoxedSelectStatement<'_, (diesel::types::Integer, diesel::types::Text, diesel::types::Text, diesel::types::Text, diesel::types::Nullable<diesel::types::Text>, diesel::types::Bool, diesel::types::Nullable<diesel::types::Timestamptz>, diesel::types::Nullable<diesel::types::Integer>, diesel::types::Text), schema::users::table, diesel::pg::Pg>: diesel::QuerySource`
   --> src/users/routes.rs:140:14
    |
140 |     source = ListData::<users::table>::set_page(map, 30, &mut source);
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: consider adding a `#![recursion_limit="128"]` attribute to your crate
    = note: required because of the requirements on the impl of `diesel::boxed_dsl::InternalBoxedDsl<'_, diesel::pg::Pg>` for `diesel::query_builder::BoxedSelectStatement<'_, (diesel::types::Integer, diesel::types::Text, diesel::types::Text, diesel::types::Text, diesel::types::Nullable<diesel::types::Text>, diesel::types::Bool, diesel::types::Nullable<diesel::types::Timestamptz>, diesel::types::Nullable<diesel::types::Integer>, diesel::types::Text), schema::users::table, diesel::pg::Pg>`

[sgrif]

This code will look fairly ugly if it's generic, but this is roughly what you'd want:

impl<T> ListData<T> where
    T: Table,
{
    pub fn set_page<'a, DB>(params: &Map, max_items: i64, source: BoxedSelectStatement<'a, T::SqlType, T, DB>) -> BoxedSelectStatement<'a, T::SqlType, T, DB> where
        DB: Backend + HasSqlType<T::SqlType>,
    {
        // your code
    }
}

You may need to disambiguate T::SqlType by writing <T as AsQuery>::SqlType.