RML006 — an operation that needs a different kind of value

push and insert need an array. A missing or null one counts as empty and is created; a value that is present and is not an array — a number, a string, an object — is a genuine mistake.

merge needs an object and does not create one, and the line between them is what the operation can supply: push hands over a complete array, while merge has only a Partial, so creating from it would mint a half-built object typed as a whole one. Use set where the object itself may be missing.

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• All diagnostics — every code the framework can report.
• Checking your app — the faults proved from the source, before anything runs.