How come sqlx::Postgres omits the Sized requirement of .bind parameter?

[jennydaman]

async fn my_query1<DB: sqlx::Database>(pool: &sqlx::Pool<DB>) -> Result<String, sqlx::Error> {
    sqlx::query_scalar("SELECT $1").bind("1".to_string()).fetch_one(pool).await  // works
}

async fn my_query2<DB: sqlx::Database>(pool: &sqlx::Pool<DB>) -> Result<String, sqlx::Error> {
    sqlx::query_scalar("SELECT $1").bind("1").fetch_one(pool).await  // Trait `Sized` is not implemented for `str` [E0277]
}

async fn my_query3<DB: sqlx::Database>(pool: &sqlx::Pool<Postgres>) -> Result<String, sqlx::Error> {
    sqlx::query_scalar("SELECT $1").bind("1").fetch_one(pool).await  // works
}