How to do nested comments

[ambroisie]

The following snippets allows one to parse identifiers separated by whitespace and ignore multi-line comments:

    let comment = seq("/*".chars()).then_ignore(take_until(seq("*/".chars())));
    let tokens = text::ident()
        .padded()
        .padded_by(comment.padded().repeated())
        .repeated();

So that the following text parses:

a
b
c
/*
*/
/* */
d
/**/
e

However, how can I define comment such that the following is valid:

/* this is /* a nested comment */ */

And this is not:

/* this is /* an unfinished comment */