The flow summary for `String#sub` leads to two new results in this test.
They are duplicates of existing results, because the query is quite
liberal in what it considers a source.
```ruby
password = "abc"
password_masked = password.sub(/./, "x")
Logger.new(STDOUT).info password_masked
```
In the example above, the query considers lines 1 and 2 to both be
sources, with a sink at line 3. Previously there was no flow from line 1
to line 3 because of the missing flow summary for `String#sub`, and
therefore there was just one result. Now we have the flow summary, there
are two results.
Line 2 is considered a source because it is an assignment to a variable
that contains the term "password". I'm not sure how to adjust the query
to avoid these duplicates, so I'm leaving them in for now.
