pub const MAX_CALL_CHAIN: usize = 8;Expand description
How many call-site spans RuntimeError::with_chain keeps, innermost
first.
A bound rather than the whole call stack, because the chain is built for
every error whether the recursion behind it was three frames deep or
the tree-walking interpreter’s 256-frame limit — and a diagnostic naming 256
callers would be unreadable long before it is untruthful. Eight is enough
to show a handful of library layers above the fault and to say, honestly,
that there were more: it is not derived from anything else that is
eight, it is simply small enough that a chain this long is already a
wall of --> blocks rather than a hint.