Empty implementations should be a one liner

[mokagio]

I'd like to suggest to add this guideline:

Preferred

struct Empty { }

Not Preferred

struct Empty {
}

struct Empty {
  // nothing to see here
}

struct Empty {

}

[nhisyam]

I am 50-50 on this. Would prefer to let it be up to the author.

[martinpilch]

One liner looks better to me