attempting to create a new type (not an alias) so that the compiler will check the arguments that i'm passing in for two different fields that are implemented in the database as the same type.

models.rs

extern crate uuid;
extern crate chrono;

extern crate bigdecimal;
extern crate num_bigint;
extern crate num_integer;
extern crate num_traits;
use schema::ledger_entries;

use self::uuid::Uuid;
use self::bigdecimal::BigDecimal;
use self::chrono::{Utc, DateTime};



// Todo: instead of making an alias
// make a newtype (trait?) so that
// the compiler doesn't allow
// a DebitAmount to be substituted
// for a CreditAmount
//
use diesel::sql_types::Numeric;
#[derive(Debug, FromSqlRow, AsExpression)]
#[sql_type = "Numeric"]
pub struct DebitAmount(BigDecimal);
pub type CreditAmount = BigDecimal;

use std::io::prelude::Write;
use diesel::serialize::{self, Output, ToSql};
impl ToSql<Numeric, Pg> for DebitAmount {
    fn to_sql<W: Write>(&self, out: &mut Output<W, Pg>) -> serialize::Result {

    }
}

use diesel::deserialize::{self, FromSql};
impl FromSql<Numeric, Pg> for DebitAmount {
    fn from_sql(bytes: Option<&[u8]>) -> deserialize::Result<Self> {

    }
}

#[derive(Queryable)]
pub struct LedgerEntry {
    pub id: Uuid,
    pub title: String,
    pub debit: Option<DebitAmount>,
    pub credit: Option<CreditAmount>,
    // DateTimes in UTC Timezone
    pub created_at: DateTime<Utc>,
    pub updated_at: Option<DateTime<Utc>>
}

#[derive(Insertable)]
#[table_name = "ledger_entries"]
pub struct NewLedgerEntry<'a> {
    pub title: &'a String,
    pub debit: &'a DebitAmount,
    pub credit: &'a CreditAmount
}