highlight numbering gaps

[daveyostcom]

message Foo {
  int32 a = 1;
  bool  b = 3;
}

Giving the 3 a different color to point out the numbering gap would be helpful.

[jvolkman]

Do you want to know that the fields are not ordered/contiguous, or that a field number is unused? I can think of reasons for fields to be listed in other than their numeric order, but I suppose each number should be used or reserved. It would probably be an optional inspection, though

[daveyostcom]

Optional would be fine. Just a highlight on a number that is not preceded by itself – 1.