"Fill struct fields" code action inside proc_macro invocation is broken by iterating the TokenStream

I hope this is the right place for this report, I have asked on the forum first.

How to reproduce

First I define two proc macros that should both just return the input stream.

#[proc_macro]
pub fn identity_correct(input: TokenStream) -> TokenStream {
    input
}

#[proc_macro]
pub fn identity_broken(input: TokenStream) -> TokenStream {
    let mut out = TokenStream::new();
    out.extend(input.into_iter());
    out
}

Then I use these proc macros on a struct expression that is incomplete:

struct Test {
    x: u32,
    y: u32,
};

fn main() {
    identity_correct!(Test { x: 0 });
    identity_broken!(Test { x: 0 });
}

When I then apply the rust-analyzer "Fill struct fields" code action on both I get the following result:

fn main() {
    identity_correct!(Test {x:0, y: todo!() });
    identity_broken!(Test {x:0, y: todo!() } });
}

Note that there is one extra closing brace } for the broken macro.

Conclusion

Clearly out.extend(input.into_iter()) loses some information and rust-analyzer can not handle it.
Since I don't use any external dependencies, this could be a bug in rust-analyzer or rust.

rust-analyzer version: 0.3.1815-standalone

rustc version: 1.77.0-nightly

Start by reproducing the "Fill struct fields" code action with the two proc macros shown in the issue, comparing direct return of the TokenStream with rebuilding it via input.into_iter(). Confirm whether the extra closing brace is introduced by rust-analyzer or by the proc-macro token representation; done means the code action produces balanced output for both examples.