Rust tokio-postgres example custom ToSql and FromSql implementation

implementation.rs

use postgres_types::{Type, ToSql, FromSql, IsNull, to_sql_checked};
use bytes::BytesMut;
use std::error::Error;

#[derive(Debug)]
struct RawValue<'a> {
    type_: Type,
    raw: Option<&'a [u8]>,
}

impl<'a> FromSql<'a> for RawValue<'a> {
    fn from_sql(
        type_: &Type, 
        raw: &'a [u8]
    ) -> Result<Self, Box<dyn Error + 'static + Send + Sync>> {
        Ok(RawValue {
            type_: type_.clone(),
            raw: Some(raw)
        })
    }
    
    fn accepts(_: &Type) -> bool {
        true
    }

    fn from_sql_null(
        type_: &Type
    ) -> Result<Self, Box<dyn Error + 'static + Send + Sync>> {
        Ok(RawValue {
            type_: type_.clone(),
            raw: None,
        })
    }
}

impl ToSql for RawValue<'_> {
     fn to_sql(
        &self, 
        type_: &Type, 
        out: &mut BytesMut
    ) -> Result<IsNull, Box<dyn Error + 'static + Send + Sync>> {
        if self.type_ != *type_ {
            return Err(format!("expected type {} but saw {}", self.type_, type_).into());
        }
        
        match self.raw {
            Some(raw) => {
                out.extend_from_slice(raw);
                Ok(IsNull::No)
            }
            None => Ok(IsNull::Yes)
        }
    }
    
    fn accepts(_: &Type) -> bool {
        true
    }
    
    to_sql_checked!();
}