[feature] Possessive quantifiers not supported (*+, ++, ?+, {n,m}+)

[jbachorik]

Summary

Possessive quantifiers (*+, ++, ?+, {n,m}+) are not supported. Like atomic groups, they match as much as possible and never give back characters to allow other parts of the pattern to match.

Examples

• \d++ — consume all digits, never backtrack
• [a-z]*+[a-z] — possessive star means the trailing [a-z] can never match (useful to express intent)
• "[^"]*+" — efficiently match a quoted string without catastrophic backtracking

Impact

• Filtered from integration test suite (reported as unsupported in testsuites/README.md)
• Possessive quantifiers are syntactic sugar for (?>X{n,m}) (atomic group wrapping a quantifier)

Implementation Notes

• Difficulty: Medium (can be desugared to atomic groups once those are supported — see companion issue [feature] Atomic groups not supported ((?>...)) #41)
• Files: RegexParser.java (parse trailing + on quantifiers), ThompsonBuilder.java
• Implement after or together with atomic groups ([feature] Atomic groups not supported ((?>...)) #41)