upgrading to data.table 12.6 breaks existing xts first(), last() dispatching. Im not sure what the last working verison was, but the broke somewhere between 12.2 and 12.6. reverting to 12.2 restores expected behavior
I am pretty sure it is my fault, made in #3859
I knew it might be breaking change thus asked for revdeps check, but it appears none of the revdeps was testing that. Thanks for reporting.