https://github.com/dhall-lang/dhall-lang/blob/60629b9d198af49984e9f9da337036942147af8b/standard/dhall.abnf

This is the ABNF file for the dhall language, it might not be a fully spec-compliant abnf but when I feed it into kgt:

$ > kgt -l abnf -e svg <./dhall-lang/standard/dhall.abnf
[1]$

it silently exits with a status 1 without producing an error message or any output.