Note: we now have a technique to avoid having to change reference line numbers when we edit the test block, which is to use the TEST_BELOW feature to have the test block at the end (see backtrace/backtrace.ml). Of course if you decide to move to that you have to change the line numbers anyway, but hopefully for the last time.

Ah, I didn't think about that. Do you think it would be a good idea to make a big PR changing all tests that check line numbers at once ? Or just switch individual tests when we need to fix line numbers ?

I'd go the incremental route, and focus only on tests whose reference output contains line numbers. You had to touch a good number of those in your fixing-flambda work, maybe you want to change them all those at once.

Well, all tests involving backtraces or compiler warnings will likely be concerned, so a global sweep of the corresponding directories would make sense too. The incremental approach still makes sense for the rest of the tests.