understanding recursive functions

Wacek Kusnierczyk wrote:

it's a pity that <<- is not explained in ?`<<-` clearly enough:

"  The operators '<<-' and '->>' cause a search to made through the
     environment for an existing definition of the variable being
     assigned.  If such a variable is found (and its binding is not
     locked) then its value is redefined, otherwise assignment takes
     place in the global environment.  Note that their semantics differ
     from that in the S language, but are useful in conjunction with
     the scoping rules of R.  See 'The R Language Definition' manual
     for further details and examples."

  

the description is further imprecise as to what happens if such a
variable is found but is locked:

foo = function() {
   x = 0
   lockBinding("x", environment())
   (function() x <<- 1)()
   unlockBinding("x", environment())
}

foo()
# error

if analysed logically (IF (found AND not locked THEN assign) ELSE assign
globally), the description is wrong.