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Pull #165

github

fix(core): iterate into an array returned by the pre-order mapper

An array returned by the mapper was a dead end: it was put in the tree as it
was, so it was not copied and none of its elements, nor their descendants,
were ever mapped or copied. There is no reason for that - an array is handed
back to the traversal now, which copies it and maps its elements in turn,
exactly like an array that was already in the tree.

Note that a rule rewriting an object into an array holding that same object
does not terminate, as the element is mapped again. This is not specific to
arrays, an object holding itself does the same, and maxStackSize catches both.

The mapping of a single object moved into mapUntilStable, which returns the
value taking the place of the object together with the context of the last
object it mapped. That drops the for(;;) with its three breaks in favour of
returns, and turns the bound on the rewrites into an ordinary counted loop
with the "did not converge" throw as its fall through. Whether the result can
be iterated into is no longer reported: the caller sees that for itself.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

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