flag unresolved symbols used as [/[[ subscripts (default false). Off by default to mute
data.table's DT[i, j, by] column masking, which flowR cannot distinguish from ordinary indexing.
flag names used as a variable read that cannot be resolved (default true). Formulas and data-masking
(dplyr/tidyr/ggplot, subset/with) are recognised via flowR's dataflow, so this is precise; residual
false positives are possible in dynamic eval/attach.
flag names used in a function-call position that cannot be resolved (default
true)