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‘predict(<rank-deficient lm>, newdata=*)’ now obeys a new argument ‘rankdeficient’ with default ‘"NA"’ which now predicts ‘NA’ (instead of somewhat dubious values) for non-estimable ‘x’. This addresses PR#15072 by Russ Lenth and is based on his original proposal and discussions in PR#16158 also by David Firth and Elin Waring. Still somewhat experimental.
When ‘UseMethod()’ cannot dispatch, it no longer segfaults producing the error message in case of a long ‘class()’, thanks to Joris Vankerschaver's report (including patch) in PR#18447.