irregex builds a POSIX leftmost-longest DFA for a pattern when it can, and jolt
used it for everything. For a pattern with an alternation whose branches have
capturing groups, that DFA leaks a non-participating branch's group: e.g.
#"(?:([0-9])|([0-9])r([0-9]+))" on "2r11" left group 1 = "2" instead of nil, so
tools.reader (rewrite-clj's dep) misread 2r1100 as 2 and 16rFF as 16.
java.util.regex is itself a leftmost-first backtracking engine, so compile a
capturing pattern with irregex's backtracking matcher ('backtrack): its submatch
semantics match the JVM and it clears a losing branch's group. Non-capturing
patterns keep the DFA — with no groups to read, its whole-match result is all a
caller sees, and it avoids backtracking's worst case. The submatch count comes
from a first cheap compile; a capturing pattern recompiles once and caches.
This clears the last rewrite-clj parser-test failure (now 772/0/0). Corpus rows
for the alternation-group case and the radix read. make test green.
7c4f9bb974