A block collection must begin on the line after its node properties, so a
block sequence whose first entry sits on the same line as its anchor or tag
('&a - x', '!!seq - x') is malformed. The parser accepted it, anchoring or
tagging the inline sequence.
parseBlockSequence now rejects a sequence whose first block entry shares a
line with the anchor or tag that introduced it, via a small helper to stay
within the complexity and brace-style limits. An anchor or tag on its own
line above the sequence, inside a sequence item ('- &a x'), before a flow
sequence ('&a [x]'), or on a scalar is unaffected; the mapping form is
left alone, since '&a key: value' is a valid anchored key.
Measured against the official YAML test-suite, parse-level conformance
rises from 267/333 (80.2%) to 268/333 (80.5%) with no regression.
Mihaela M
28f549311f