XSD 1.0 Datatypes Appendix F defines SingleCharNoEsc as [^\[\]] and admits a
nested class only as a -[...] subtraction, so a `[` inside a character class
that is not introduced by `-` is a syntax error. RegexParser treated such a
`[` as a literal scalar, so `[a[:xyz:]` compiled and the schema declaring it
was wrongly accepted (XSTS RegexTest_993, RegexTest_1477).
nextClassMember now throws a dedicated RegexError.unescapedClassBracket, kept
distinct from the generic, deliberately-lenient badClass so the change cannot
regress a valid-but-unsupported pattern. XSDSimpleParser.rejectsPattern treats
it as a genuine syntax error, so the declaring schema is invalid.
Closes RegexTest_993 and RegexTest_1477: invalid-schemas-accepted 15 -> 13,
valid-schemas-rejected held at 0, instance buckets unchanged (full XSTS
archive). Escaped [a\[c] and subtraction [a-z-[aeiou]] stay valid; the
unterminated case [a[:xyz: now faults on the inner [.
Mihaela Mihaljevic
ba934bbb58