Check if CI runs through #7
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This is the first step to supporting captureless lookbehind assertions
The lack of recursing into the inner expression of a lookaround is correct under the current assumption that lookarounds cannot have capture groups. But once the restriction is lifted, this wrong implementation can be very subtle to find. Instead, we can already do the filtering and accept it being a no-op for now.
This makes it consistent with parser's ErrorKind::UnsupportedLookAround.
We require two vm instructions 'CheckLookaround' and 'WriteLookaround' to be able to track the state of lookaround expressions at the current position in the haystack. Both instructions access a new 'lookaround' vector of booleans, which contains one entry per lookaround expression in the regex.
These changes implement the compilation of lookaround assertions from HIR to NFA. Subexpressions of lookaround assertions are patched to a top level reverse union. This is necessary so that the NFA will explore the innermost subexpression first and thereby make sure that all subexpression results are available when they need to be checked. I.e. any `WriteLookaround` state must be visited before any `CheckLookaround` state with the same index.
The machinery necessary to perform the parallel lookbehind checking should only be compiled in when there is actually a lookbehind expression in the regex. This restores compilation to the expected outputs for regexes without lookbehind expressions.
This makes it so we don't need to reset the lookaround state on each character advancement.
Rename certain enums to be consistent with rest of codebase.
We need to disable pre-filters when a regex contains lookarounds. This is because the relevant information for a lookbehind can be before the start of the match.
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Not to be merged; this is simply to trigger CI and check if everyting is ok before we open the PR to the main repo