There is a test that happens to want it this way
shawnl on May 26 2019, 8:45 AM.Authored by
Before we go any further here, I'd suggest to revert all the switch related changes that have landed for now. They've had a lot of test fallout, and it looks like they broke the ubsan (and msan and asan) builders (see e.g. http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-bootstrap-ubsan/builds/13084) in a way that looks like a miscompile of the clang bootstrap to me. Hard to tell which change exactly is at fault as multiple were pushed at the same time. As such I'd suggest to revert back to a green build and then reapply changes more carefully, such that tests pass for each individual commit.