I'm trying to find a safe spot in the middle of a file, where I can start parsing, normally you have to parse the entire file to understand it, ex with your grammar files, there are many keywords inside huge strings, so basically I let the compiler handle comments and white-space parsing, which allows to me to make a stable localized parser for a subset of the language.

What I don't get is how the [__LINE__] part in magic contains significant
info.

It allows me to retrieve the entire original source for a declaration... it kinda emulates a ".sourceof" trait / property. :)