this regression is hard to minimize but I'm getting with DMD64 D Compiler v2.071.0 (dmd from homebrew) duplicate symbol _D4core4sync5mutex5Mutex12MonitorProxy6__initZ in: /tmp/.rdmd-501/rdmd-project_run.d-XXX/z01.o ~/homebrew/lib//libphobos2.a(mutex_39c_213.o) ld: 1 duplicate symbol for architecture x86_64 which corresponds to: core.sync.mutex.Mutex.MonitorProxy.__init this was after an invocation of rdmd (ie of dmd...)
seems fixed in 2.071.1.b2
I'm not going to worry about it if it appears to be working.