Question about 'struct update syntax'

[maozx]

I'm learning Rust. I have a puzzle that I want to be answered:

/// struct User
#[derive(Debug)]
struct User {
    id: usize,
    name: String,
    age: u8,
}
fn main() {
    let old_user = User {
        id: 1001,
        name: String::from("allen"),
        age: 23,
    };
    let new_user = User {
        id: 1002,
        ..old_user
    };
    // it will give a error because 'name' has been removed
    println!("{:?}", old_user);
    // but it works
    println!("{}", old_user.id);
}

why can this be?

[maozx]

[vague]

The entire expression uses the given values for the fields that were specified and moves or copies the remaining fields from the base expression.
src: Reference: functional update syntax

[abdavis]

This is actually a kind of new feature. It's a Partial move

[abdavis]

Actually this link is a bit better of an explanation

[quinedot]

In case it wasn't clear from the other comments, partial moves aren't a struct update specific thing. The other thing to note is that struct update works like this, and not like this.

[maozx]

yes, I understand how it works.
and the article given by abdavis also clearly illustrates this point.

I just had a simple and crude idea:
either clone the ‘name’ to new_user, either deprecated the old_user entirely.

[maozx]

yes. it explains why

println!("{}", old_user.id);

works.

The final conclusion is: i can use 'old_user.xx' but i can't use 'old_user'.
It confuses me as to whether I should use 'old_user' anymore