`unexpected end of macro invocation` when passing no parameters to debug macro.

[cedws]

When I pass no parameters to debug!(), like so,

debug!();

the program will exit with the error unexpected end of macro invocation. The expected behavior is that an empty line should be printed, as it is with println!().

[sfackler]

I think the situation is a bit different here compared to println as different log lines are more separate than standard output is. Why do you want to log no information?

[cedws]

It's an easy way of printing a line break.

[dekellum]

This might be of more obvious value with #296, e.g. logging with structured values only, and no unstructured message?

Also an obvious workaround with current log is debug!(""), which works as expected.

Logging implementations could still decide, or be configured, to filter both debug!(""), any future supported debug!(), and debug!("\n") for that matter, if these log messages are viewed more as an abuse of the logging system.

[dekellum]

Also the error message for an empty log macro invocation, is now even stranger than the OP's title, see below. I would imagine, if this should remain a compile time error, that a PR would be favorably considered to improve the error message:

Link to playground:

error: expected identifier, found `,`
 --> src/main.rs:9:5
  |
9 |     info!();
  |     ^^^^^^^^
  |     |
  |     expected identifier
  |     help: remove this comma
  |
  = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)