It's failing on macOS under AddressSanitizer for no obvious reason - i.e., no report is produced, just the code isn't working correctly. Might possibly be a bug in ASan but I want to silence an internal buildbot before a deeper investigation. I didn't try platforms other than macOS.
The failure can be reproduced somewhere around rG0b2a92224630f6e177d091b8391cfa943764aba5 by self-hosting. The unittest has to be compiled as -DCMAKE_BUILD_TYPE=Release -DLLVM_USE_SANITIZER="Address" in order to reproduce the issue (RelWithDebInfo works too, but not Debug).