NEWS for separately-fixed bug

Author: MichaelChirico

NEWS.md

@@ -123,6 +123,8 @@ rowwiseDT(
 
 16. Joins of `integer64` and `double` columns succeed when the `double` column has lossless `integer64` representation, [#4167](https://github.com/Rdatatable/data.table/issues/4167) and [#6625](https://github.com/Rdatatable/data.table/issues/6625). Previously, this only worked when the double column had lossless _32-bit_ integer representation. Thanks @MichaelChirico for the reports and fix.
 
+17. Assignment with `:=` to an S4 slot of an under-allocated data.table now works, [#6704](https://github.com/Rdatatable/data.table/issues/6704). Thanks @MichaelChirico for the report and fix.
+
 ## NOTES
 
 1. There is a new vignette on joins! See `vignette("datatable-joins")`. Thanks to Angel Feliz for authoring it! Feedback welcome. This vignette has been highly requested since 2017: [#2181](https://github.com/Rdatatable/data.table/issues/2181).

inst/tests/S4.Rraw

@@ -115,5 +115,6 @@ setClass("DataFrame", slots=c(x="data.frame"))
 DF = new("DataFrame", x=data.frame(a=1))
 setDT(DF@x)
 test(7.1, is.data.table(DF@x))
+# Similar code for under-allocated data.tables in S4 slots, #6704
 setClass("DataTable", slots=c(x="data.table"))
 test(7.2, options=c(datatable.alloccol=0L), {DT = new("DataTable", x=data.table(a=1)); DT@x[, b := 2L]; DT@x$b}, 2L) # NB: requires assigning DT to test assignment back to that object