chore: remove duplicate macro partially_shredded_variant_array_gen

[codephage2020]

Which issue does this PR close?

• Closes Duplicate macro definition: partially_shredded_variant_array_gen #9492 .

Rationale for this change

What changes are included in this PR?

Are these changes tested?

YES

Are there any user-facing changes?

NO

[klion26]

@codephage2020, thanks for the improvement, LGTM. This must have been left behind when I resolved a conflict.

[scovich]

I'm a bit surprised the duplication didn't trigger compiler errors?
But removing it also doesn't trigger any errors, so LGTM.

[codephage2020]

I'm a bit surprised the duplication didn't trigger compiler errors?

It could be because the two macros have different parameter names?

[klion26]

I'm a bit surprised the duplication didn't trigger compiler errors? But removing it also doesn't trigger any errors, so LGTM.

Tried that

• Same macro will override the previous one (same as variable)
• Function will throw an error

same macro

macro_rules! my_macro {
    () => { println!("first"); };
}

macro_rules! my_macro {
    () => { println!("second"); };
}

fn main() {
    my_macro!(); // 输出 "second"
}

the output will be

warning: unused macro definition: `my_macro`
 --> src/main.rs:1:14
  |
1 | macro_rules! my_macro {
  |              ^^^^^^^^
  |
  = note: `#[warn(unused_macros)]` (part of `#[warn(unused)]`) on by default

warning: `playground` (bin "playground") generated 1 warning
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.79s
     Running `target/debug/playground`

same fun

fn my_fn() {
    println!("first");
}

fn my_fn() { // 编译错误：the name `my_fn` is defined multiple times
    println!("second");
}
fn main() {
    my_fn!();
}

will compile error

   Compiling playground v0.0.1 (/playground)
error[E0428]: the name `my_fn` is defined multiple times
 --> src/main.rs:5:1
  |
1 | fn my_fn() {
  | ---------- previous definition of the value `my_fn` here
...
5 | fn my_fn() { // 编译错误：the name `my_fn` is defined multiple times
  | ^^^^^^^^^^ `my_fn` redefined here
  |
  = note: `my_fn` must be defined only once in the value namespace of this module

error: cannot find macro `my_fn` in this scope
 --> src/main.rs:9:5
  |
9 |     my_fn!();
  |     ^^^^^
  |
  = note: `my_fn` is in scope, but it is a function, not a macro

For more information about this error, try `rustc --explain E0428`.
error: could not compile `playground` (bin "playground") due to 2 previous errors

[codephage2020]

CC @scovich @klion26
I've reproduced the scenario and identified the cause: Rust does not check for duplicate macros, only for unused ones. The following example, which is identical to the original code, does not trigger an error.

fn main() {
    macro_rules! my_macro {
        () => { println!("first"); };
    }
    my_macro!();

    macro_rules! my_macro {
        () => { println!("second"); };
    }
    my_macro!();
}

output(NO WARNING)

first
second