error: removing an expression is not supported in this position
  --> $DIR/cfg-method-receiver.rs:9:17
   |
LL |     cbor_map! { #[cfg(test)] 4};
   |                 ^^^^^^^^^^^^

error[E0689]: can't call method `signum` on ambiguous numeric type `{integer}`
  --> $DIR/cfg-method-receiver.rs:3:14
   |
LL |         $key.signum();
   |              ^^^^^^
...
LL |     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`
   |
LL |     cbor_map! { #[cfg(test)] 4_i32};
   |                              ~~~~~

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0689`.