Self-describing numbers

You are encouraged to solve this task according to the task description, using any language you may know.
There are several so-called "self-describing" or "self-descriptive" integers.

An integer is said to be "self-describing" if it has the property that, when digit positions are labeled 0 to N-1, the digit in each position is equal to the number of times that that digit appears in the number.

For example,   2020   is a four-digit self describing number:

   position   0   has value   2   and there are two 0s in the number;
   position   1   has value   0   and there are no 1s in the number;
   position   2   has value   2   and there are two 2s;
   position   3   has value   0   and there are zero 3s.


Self-describing numbers < 100.000.000  are:     1210,   2020,   21200,   3211000,   42101000.



Task Description
 Write a function/routine/method/... that will check whether a given positive integer is self-describing.
 As an optional stretch goal - generate and display the set of self-describing numbers.


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procedure count (test_item, str)
  result := 0
  every item := !str do 
    if test_item == item then result +:= 1
  return result
end
 
procedure is_self_describing (n)
  ns := string (n) # convert to a string
  every i := 1 to *ns do {
    if count (string(i-1), ns) ~= ns[i] then fail
  }
  return 1 # success
end
 
# generator for creating self_describing_numbers
procedure self_describing_numbers ()
  n := 1
  repeat {
    if is_self_describing(n) then suspend n
    n +:= 1
  }
end
 
procedure main ()
  # write the first 4 self-describing numbers
  every write (self_describing_numbers ()\4)
end
 