Trait ComparisonOperand 

pub trait ComparisonOperand<'a, V, Expected>: ToSQL<'a, V>
where
    V: SQLParam + 'a,
    Expected: DataType,
{
    type SQLType: DataType;
    type Aggregate: AggregateKind;
}

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, Expected> where Expected is the left-hand side’s SQL type.

The blanket impl below only fires when Expected: Compatible<R::SQLType>, so passing an incompatible type (e.g. comparing Int with Text) fails at compile time with a clear diagnostic.

Required Associated Types

type SQLType: DataType

type Aggregate: AggregateKind

Implementors

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

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

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

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