Mmmm, I see what you're getting at. Maybe it's a wimp-out
but how about:
It is an error to use the named structure in the definition
of a letrec variable as an argument to a strict operator
during the evaluation of its definition.
e.g. (letrec ((foo (+ 1 foo))) <---- error
(letrec ((bar (cons 42 bar))) <--- ok.
Rice.
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