Originally posted by @OskarStark in #39457 (comment)

Oh I've done that, but we have a "bigger" problem here.

should return string, but it contains null whenever you instantiate the Dsn class vie new instead of fromString()

One option could be to change the return type to ?string or make the constructor private and only instantiate through fromString. Currently new Dsn(...) is only used in tests. 🤔