The JSON.parse-with-source proposal (now part of ES2026) gives a
reviver a third "context" argument. For a primitive value that was
not modified by an earlier reviver call, the context has a "source"
property holding the matched JSON source text; for objects, arrays,
and forward-modified values it is an empty object.
We already had JSON.rawJSON and JSON.isRawJSON, but the reviver only
received two arguments. Implement the missing half by building a JSON
Parse Record snapshot while parsing: each primitive records the
trimmed raw token from simdjson, and arrays and objects record their
child records keyed by index and property name. InternalizeJSONProperty
threads the matching record down the tree, creates the context object,
and only attaches "source" when the record's stored value still equals
the live value (SameValue), which suppresses source for values a
reviver replaced or appended.
The record values live in heap storage the GC does not scan, and a
reviver can detach the originals from the object graph mid-walk, so
the snapshot's values are kept rooted for the duration of the walk.
Closes the six json-parse-with-source test262 failures and adds
test-js coverage for primitive source text and forward modification.
a3db2d1986