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/// This will implement `SelectableExpression` and `AppearsOnTable` for "simple"
/// composite nodes where the where clause is roughly `AllTyParams:
/// SelectableExpression<QS>, Self: Expression`.
///
/// This macro is exported because we want to be able to call it from other
/// macros that are exported, but it is not part of our public API.
#[macro_export(local_inner_macros)]
#[doc(hidden)]
macro_rules! impl_selectable_expression {
    ($struct_name:ident) => {
        impl_selectable_expression!(ty_params = (), struct_ty = $struct_name,);
    };

    ($struct_name:ident<$($ty_params:ident),+>) => {
        impl_selectable_expression!(
            ty_params = ($($ty_params),+),
            struct_ty = $struct_name<$($ty_params),+>,
        );
    };

    (ty_params = ($($ty_params:ident),*), struct_ty = $struct_ty:ty,) => {
        impl<$($ty_params,)* QS> $crate::expression::SelectableExpression<QS>
            for $struct_ty where
                $struct_ty: $crate::expression::AppearsOnTable<QS>,
                $($ty_params: $crate::expression::SelectableExpression<QS>,)*
        {
        }

        impl<$($ty_params,)* QS> $crate::expression::AppearsOnTable<QS>
            for $struct_ty where
                $struct_ty: $crate::expression::Expression,
                $($ty_params: $crate::expression::AppearsOnTable<QS>,)*
        {
        }
    };
}