Function sql::plan::query::plan_case

fn plan_case<'a>(
    ecx: &ExprContext<'_>, 
    operand: &'a Option<Box<Expr<Aug>>>, 
    conditions: &'a [Expr<Aug>], 
    results: &'a [Expr<Aug>], 
    else_result: &'a Option<Box<Expr<Aug>>>
) -> Result<HirScalarExpr, PlanError>