Context

In PACK we charge 3 costs:

strip_locations, done well, not changed;
to_bytes expr_encoding, done after the fact, not fixed here;
Bytes.cat, done after the fact, now done before, charged like to_bytes, now charged like Bytes.cat.

Manually testing the MR

Document the interface of any function added or modified (see the coding guidelines)
Document any change to the user interface, including configuration parameters (see node configuration)
Provide automatic testing (see the testing guide).
For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, the Development Version section of CHANGES.md for everything else).
Select suitable reviewers using the Reviewers field below.
Select as Assignee the next person who should take action on that MR

Edited Oct 08, 2021 by Mehdi Bouaziz