Invalid token error when dependency artifact starts with a number

[sanel]

• Updating to using the latest released version of Leiningen (lein upgrade).
• Moving your ~/.lein/profiles.clj (if present) out of the way. This contains third-party dependencies and plugins that can cause problems inside Leiningen.
• Updating any old versions of plugins in your project.clj, especially if the problem is with a plugin not working. Old versions of plugins like nREPL and CIDER (as well as others) can cause problems with newer versions of Leiningen.
• (If you are using Java 9 or newer), updating your dependencies to their most recent versions. Recent JDK's have introduced changes which can break some Clojure libraries.

Describe the bug
When the project dependency artifact starts with a number, leiningen will throw java.lang.RuntimeException: Invalid token error.

To Reproduce
Steps to reproduce the behavior:

1. Create a new project demo.
2. Copy/paste in project.clj the code down below

(defproject demo "0.1.0-SNAPSHOT"
  :dependencies [[org.clojure/clojure "1.10.1"]
                 [com.github.2captcha/2captcha-java "1.0.1"]]
  :repl-options {:init-ns demo.core})

After running lein deps, it will throw exception:

...
Caused by: java.lang.RuntimeException: Invalid token: com.github.2captcha/2captcha-java
 at clojure.lang.Util.runtimeException (Util.java:221)
    clojure.lang.LispReader.interpretToken (LispReader.java:412)
    clojure.lang.LispReader.read (LispReader.java:305)
...

Workaround is to set dependency as a string, e.g.

["com.github.2captcha/2captcha-java" "1.0.1"]

Expected behavior
Leiningen should download 2captcha library.

Environment

• Leiningen Version: 2.9.6
• JDK Version: 1.8.0_292 OpenJDK 64-Bit
• OS: Slackware 14.2 64-Bit

[technomancy]

Leiningen uses the Clojure reader to load project.clj files, and thus it is subject to the limitations of Clojure when it comes to rules about what constitutes a valid symbol. The desired behavior is not really possible without completely rewriting the project-loading code. The best we can do is offer a workaround as documented near the end of the FAQ.