A node property always attaches to a node, and an empty node is allowed, so
an anchor or tag with nothing after it (a bare '&anchor', a 'key: &a', or a
'!!str'/'!!null' with no value) denotes that property applied to a null
node. parseNode rejected it as a missing node.
parseNode now emits a null scalar carrying the properties when a node
position holds only an anchor or tag, via a small helper to stay within the
complexity limit; with no properties, a missing node is still an error. A
'!!str' empty node resolves to the empty string and '!!null' to null. The
error-path test that asserted a dangling property throws is corrected, as
the construct is valid per the grammar and the official test-suite.
Measured against the official YAML test-suite, parse-level conformance
rises from 287/333 (86.2%) to 288/333 (86.5%), with value-level up one and
no regression.
Fill the highest-value coverage gaps found in the Codable bridge and
parser: the full integer-width decode ladder and per-width out-of-range
errors, Float round-trip, NaN equality and hash consistency (the bespoke
nan == nan invariant), unkeyed decodeNil false-branch and nested-index
mismatch, and the previously untested expectedNode, unterminated flow
mapping, explicit block-scalar under-indent, and buffered invalid-merge
error paths.
