RestartableLexer

Hello,

As I proceed with my custom language plugin, I am getting spurious crashes.

@NotNull method com/intellij/openapi/editor/ex/util/SegmentArrayWithData.unpackTokenFromData must not return null

If I am correct, this is something I can cure by implementing RestartableLexer.

Documentation I googled for ResatrtableLexer is next to nonexistent. I am using JFlex and Grammar Kit. Any tutorial or example on what I have to do to switch from FlexLexer to RestartableLexer - and is it what I have to do here?

TIA, dd