[REGEX] Non fixed-length lookbehind support

[jerryc05]

I am writing a extension for language syntax highlighting, and I would like to use non fixed-length lookbehind regex like (?<=void[ \t]+)\w+ to highlight function name, but it does not work. However, fixed-length lookbehind works. Is there any way to fix this, or any workarounds? Thx.

[vscodebot]

(Experimental duplicate detection)
Thanks for submitting this issue. Please also check if it is already covered by an existing one, like:

• Syntax highlight regex in find in file/s when regex is enabled (#42715)

[dbaeumer]

@aeschli @alexandrudima since this is TextMate, any idea.

[jerryc05]

Okay one possible solution is to move [ \t]+ out of the lookbehind block, and that worked fine.

But what if there are more modifiers like public void funcNameToCatch()?

[aeschli]

TextMate Grammars use Oniguruma as RegExp engine. The spec there says:

Subexp of look-behind must be fixed character length.
                     But different character length is allowed in top level
                     alternatives only.
                     ex. (?<=a|bc) is OK. (?<=aaa(?:b|cd)) is not allowed.