ices/73663.rs: fixed with errors

[github-actions]

Issue: rust-lang/rust#73663

macro_rules! cbor_map {
    ($key:expr) => {
        $key.signum();
    };
}

fn main() {
    cbor_map! { #[cfg(test)] 4};
}

=== stdout ===
=== stderr ===
error[E0658]: attributes on expressions are experimental
 --> /home/runner/work/glacier/glacier/ices/73663.rs:8:17
  |
8 |     cbor_map! { #[cfg(test)] 4};
  |                 ^^^^^^^^^^^^
  |
  = note: see issue #15701 <https://github.com/rust-lang/rust/issues/15701> for more information
  = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable

error: removing an expression is not supported in this position
 --> /home/runner/work/glacier/glacier/ices/73663.rs:8:17
  |
8 |     cbor_map! { #[cfg(test)] 4};
  |                 ^^^^^^^^^^^^

error[E0689]: can't call method `signum` on ambiguous numeric type `{integer}`
 --> /home/runner/work/glacier/glacier/ices/73663.rs:3:14
  |
3 |         $key.signum();
  |              ^^^^^^
...
8 |     cbor_map! { #[cfg(test)] 4};
  |     --------------------------- in this macro invocation
  |
  = note: this error originates in the macro `cbor_map` (in Nightly builds, run with -Z macro-backtrace for more info)
help: you must specify a concrete type for this numeric value, like `i32`
  |
8 |     cbor_map! { #[cfg(test)] 4_i32};
  |                              ~~~~~

error: aborting due to 3 previous errors

Some errors have detailed explanations: E0658, E0689.
For more information about an error, try `rustc --explain E0658`.
==============