diesel/query_dsl/
boxed_dsl.rs

1use crate::dsl;
2use crate::expression::TypedExpressionType;
3use crate::expression::ValidGrouping;
4use crate::query_builder::AsQuery;
5use crate::query_builder::FromClause;
6use crate::query_builder::SelectStatement;
7use crate::query_source::Table;
8use crate::Expression;
9
10/// The `into_boxed` method
11///
12/// This trait should not be relied on directly by most apps. Its behavior is
13/// provided by [`QueryDsl`]. However, you may need a where clause on this trait
14/// to call `into_boxed` from generic code.
15///
16/// [`QueryDsl`]: crate::QueryDsl
17#[diagnostic::on_unimplemented(
18    message = "cannot box `{Self}` for backend `{DB}`",
19    note = "this either means `{Self}` is no valid SQL for `{DB}`",
20    note = "or this means `{Self}` uses clauses not supporting boxing like the `LOCKING` or `GROUP BY` clause"
21)]
22pub trait BoxedDsl<'a, DB> {
23    /// The return type of `internal_into_boxed`
24    type Output;
25
26    /// See the trait documentation.
27    fn internal_into_boxed(self) -> dsl::IntoBoxed<'a, Self, DB>;
28}
29
30#[diagnostic::do_not_recommend]
31impl<'a, T, DB> BoxedDsl<'a, DB> for T
32where
33    T: Table + AsQuery<Query = SelectStatement<FromClause<T>>>,
34    SelectStatement<FromClause<T>>: BoxedDsl<'a, DB>,
35    T::DefaultSelection: Expression<SqlType = T::SqlType> + ValidGrouping<()>,
36    T::SqlType: TypedExpressionType,
37{
38    type Output = dsl::IntoBoxed<'a, SelectStatement<FromClause<T>>, DB>;
39
40    fn internal_into_boxed(self) -> Self::Output {
41        self.as_query().internal_into_boxed()
42    }
43}
diesel/query_dsl/boxed_dsl.rs

diesel/query_dsl/
boxed_dsl.rs
