Trailing comma in `fmt!` macro

[Darksonn]

This code:

pr_warn!(
    "{}:{} transaction to {} failed: {source:?}",
    info.from_pid,
    info.from_tid,
    info.to_pid,
);

results in this error:

error: expected expression, found `,`                                 
    --> linux/drivers/android/binder/thread.rs:1257:21                                                
     |                                                                                                                                       
1257 |                     "{}:{} transaction to {} failed: {source:?}",   
     |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected expression

Because of the trailing comma after info.to_pid. This should be fixed so that trailing commas are allowed. I think the problem is in the fmt! proc macro, which is defined in rust/macros/fmt.rs.

---

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[ojeda]

I think this is #1172.

[jw2476]

Had a quick go at this one, it's my first patch, so apologies in advance if there are any issues.
https://lore.kernel.org/rust-for-linux/20260306174126.76296-1-jackwh.whitehorn@gmail.com/