Summary

value_of and value_of_ref fixes

Tests

python3 ./runTests.py -j6 ./test/prob/gamma/
python3 ./runTests.py -j6 --run-all ./test/unit/ -f gamma_lcc 

Side Effects

Are there any side effects that we should be aware of?

Release notes

Replace this text with a short note on what will change if this pull request is merged in which case this will be included in the release notes.

Checklist

• Copyright holder: Simons Foundation

  The copyright holder is typically you or your assignee, such as a university or company. By submitting this pull request, the copyright holder is agreeing to the license the submitted work under the following licenses:
  - Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
  - Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

• the basic tests are passing

  • unit tests pass (to run, use: ./runTests.py test/unit)
  • header checks pass, (make test-headers)
  • dependencies checks pass, (make test-math-dependencies)
  • docs build, (make doxygen)
  • code passes the built in C++ standards checks (make cpplint)

• the code is written in idiomatic C++ and changes are documented in the doxygen

• the new changes are tested