Auto merge of #29682 - Ryman:dead_spam, r=sanxiyn

This standardises the current behavior to match `enum` variants, hopefully leading to less warning spam for users!

For example the code below will have 2 warnings (for `Foo` and `Bar`) rather than 7:
```rust
enum Foo {
    A,
    B { a: String, b: isize },
    C
}

struct Bar {
    a: i32,
    b: String,
    c: ()
}

fn main() {
    println!("Hi")
}
```
http://is.gd/zAztKW

0 files changed, 0 insertions, 0 deletions