Failed parsing lookbehind expressions

[HoldYourWaffle]

Looks like lookbehind-expressions are not supported (yet):

Error: Unable to use "first char" lexer optimizations:
	Failed parsing: < /(?<=FUNCTION(\s+)([a-zA-Z]\w*)(\s*)){(\\}|[^}])*}/ >
	Using the regexp-to-ast library version: 0.4.0
	Please open an issue at: https://github.com/bd82/regexp-to-ast/issues

As you can see I was told to open an issue, so here it is 😄

My pattern is:

/(?<=FUNCTION(\s+)([a-zA-Z]\w*)(\s*)){(\\}|[^}])*}/

but it happens for any kind of lookbehind expression ((?<=x)y).

[bd82]

Yeah I have not implemented that feature or other newer RegExp features.
Although I doubt it should be too complex as it is very similar to lookahead...