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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import Foundation
 
extension BinaryInteger {
  @inlinable
  public var isSelfDescribing: Bool {
    let stringChars = String(self).map({ String($0) })
    let counts = stringChars.reduce(into: [Int: Int](), {res, char in res[Int(char), default: 0] += 1})
 
    for (i, n) in stringChars.enumerated() where counts[i, default: 0] != Int(n) {
      return false
    }
 
    return true
  }
}
 
print("Self-describing numbers less than 100,000,000:")
 
DispatchQueue.concurrentPerform(iterations: 100_000_000) {i in
  defer {
    if i == 100_000_000 - 1 {
      exit(0)
    }
  }
 
  guard i.isSelfDescribing else {
    return
  }
 
  print(i)
}
 
dispatchMain()