use serde::Deserialize;
#[derive(Deserialize, serde_derive_default::Default)]
struct Test {
#[serde(default = "default")]
field_1: usize,
#[serde(rename = "field2", default = "default", flatten)]
field_2: usize,
test_str: String,
}
fn default() -> usize {
1
}
fn main() {
Test::default();
}