Trait ComparisonOperand 

pub trait ComparisonOperand<'a, V, L>: Sized
where
    V: SQLParam + 'a,
    L: Expr<'a, V>,
{
    type SQLType: DataType;
    type Aggregate: AggregateKind;

    // Required method
    fn into_comparison_sql(self) -> SQL<'a, V>;
}

Type-safe operand for comparison functions.

This trait exists as an indirection layer between comparison functions (eq, gt, like, etc.) and the Expr trait. Rather than accepting any Expr directly, comparisons require ComparisonOperand<'a, V, L> where L is the left-hand expression type.

The blanket impl below only fires when L::SQLType: Compatible<R::SQLType>. Table macros can also implement this trait for custom column value types and a specific generated column ZST, which enables eq(table.custom, value) without making the value type a global SQL expression.

Required Associated Types

type SQLType: DataType

type Aggregate: AggregateKind

Required Methods

fn into_comparison_sql(self) -> SQL<'a, V>

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors

impl<'a, V, L, R> ComparisonOperand<'a, V, L> for R

where V: SQLParam + 'a, L: Expr<'a, V>, R: Expr<'a, V>, L::SQLType: Compatible<R::SQLType>,

type SQLType = <R as Expr<'a, V>>::SQLType

type Aggregate = <R as Expr<'a, V>>::Aggregate