Parsing an empty input where the grammar doesn’t allow an empty input eventually calls this line when reporting the error:

org.spoofax.jsglr.client.imploder.AbstractTokenizer @ 306

The offset here is 0, and the length of the input is 0, causing the offset that’s passed to makeErrorAdjunctBackwards()
to be -1. This negative value is then passed down until it fails the assertion here:

org.spoofax.jsglr.client.imploder.LineStartOffsetList @ 37

Submitted by D. Pelsmaeker on 16 February 2016 at 17:39