library(data.table)
z = 4
test.data.table()

Error in test.data.table() : 
  3 errors out of 9118 in 00:01:00 elapsed (00:02:40 cpu) on Thu Jul 11 08:46:42 2019. [endian==little, sizeof(long double)==16, sizeof(pointer)==8, TZ=Asia/Singapore, locale='LC_CTYPE=en_US.UTF-8;LC_NUMERIC=C;LC_TIME=en_US.UTF-8;LC_COLLATE=en_US.UTF-8;LC_MONETARY=en_US.UTF-8;LC_MESSAGES=en_US.UTF-8;LC_PAPER=en_US.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_US.UTF-8;LC_IDENTIFICATION=C', l10n_info()='MBCS=TRUE; UTF-8=TRUE; Latin-1=FALSE', getDTthreads()='omp_get_num_procs()==8; R_DATATABLE_NUM_PROCS_PERCENT=="" (default 50); R_DATATABLE_NUM_THREADS==""; omp_get_thread_limit()==2147483647; omp_get_max_threads()==8; OMP_THREAD_LIMIT==""; OMP_NUM_THREADS==""; data.table is using 4 threads. This is set on startup, and by setDTthreads(). See ?setDTthreads.; RestoreAfterFork==true']. Search tests/tests.Rraw for test numbers: 1894.09, 1894.13, 1894.14

if (exists("z")) rm(z)
test(1894.09, DT[, sum(z)*..z], error="Variable 'z' is not found in calling scope. Looking in calling scope because this symbol was prefixed with .. in the j= parameter.")
z = 3L
test(1894.10, DT[, sum(z)*..z], 72L)
setnames(DT, "z", "..z")
test(1894.11, DT[, sum(y)*..z], INT(105,120,135))
rm(z)
test(1894.12, DT[, sum(y)*..z], INT(105,120,135))
setnames(DT, "..z", "z")
test(1894.13, DT[, sum(y)*..z], error="Variable 'z' is not found in calling scope")
..z = 4L
test(1894.14, DT[, sum(y)*..z], 60L)  # 'manual' prefix (we have recommended in the past) still works, for now.