Cannot generate railroad diagrams for ABNF files from the examples

[ashwin]

I tried to generate railroad diagram for the TOML file format's ABNF grammar and it failed silently:

$ kgt -l abnf -e rrtext < toml.abnf

There are 5 ABNF example files that ship with kgt:

$ ls -1 examples/*.abnf
examples/abnf.abnf
examples/datetime.abnf
examples/irc.abnf
examples/postal.abnf
examples/utf8.abnf

kgt is able to generate railroad diagrams only for 2 of them. The following 3 ABNF files do not product any output:

$ kgt -l abnf -e rrtext < examples/abnf.abnf
$ kgt -l abnf -e rrtext < examples/irc.abnf
$ kgt -l abnf -e rrtext < examples/postal.abnf

What am I doing wrong? 🤔