Support deserializing flattened fields in csv

[dtolnay]

#[macro_use]
extern crate serde_derive;

extern crate serde;
extern crate csv;

#[derive(Debug, Deserialize)]
struct Record {
    city: String,
    region: String,
    country: String,
    #[serde(flatten)]
    dem: Demographics,
}

#[derive(Debug, Deserialize)]
struct Demographics {
    population: u64,
}

const INPUT: &[u8] = b"\
city,region,country,population
Southborough,MA,United States,9686
Northbridge,MA,United States,14061
Westborough,MA,United States,29313
Marlborough,MA,United States,38334
Springfield,MA,United States,152227
Springfield,MO,United States,150443
Springfield,NJ,United States,14976
Springfield,OH,United States,64325
Springfield,OR,United States,56032
Concord,NH,United States,42605";

fn main() {
    let mut input = INPUT;
    let mut rdr = csv::Reader::from_reader(&mut input);
    for record in rdr.deserialize::<Record>() {
        println!("{:?}", record.unwrap());
    }
}

CSV deserialize error: record 1 (line: 2, byte: 31): missing field `population`

[dtolnay]

Fixed in ea0012f.

Record { city: "Southborough", region: "MA", country: "United States", dem: Demographics { population: 9686 } }
Record { city: "Northbridge", region: "MA", country: "United States", dem: Demographics { population: 14061 } }
Record { city: "Westborough", region: "MA", country: "United States", dem: Demographics { population: 29313 } }
Record { city: "Marlborough", region: "MA", country: "United States", dem: Demographics { population: 38334 } }
Record { city: "Springfield", region: "MA", country: "United States", dem: Demographics { population: 152227 } }
Record { city: "Springfield", region: "MO", country: "United States", dem: Demographics { population: 150443 } }
Record { city: "Springfield", region: "NJ", country: "United States", dem: Demographics { population: 14976 } }
Record { city: "Springfield", region: "OH", country: "United States", dem: Demographics { population: 64325 } }
Record { city: "Springfield", region: "OR", country: "United States", dem: Demographics { population: 56032 } }
Record { city: "Concord", region: "NH", country: "United States", dem: Demographics { population: 42605 } }