No realloc warning when adding many columns in a loop, inside a function

[mattdowle]

> packageVersion("data.table")
[1] ‘1.9.7’
> x = data.table(a=1:3)
> truelength(x)
[1] 100
> f = function(DT) {
+  for (i in 1:200) {
+    DT[,paste0("new",i):=1:3]
+  }
+ }
> f(x)            # I thought there was a warning here that := on i==100 did a realloc
> dim(x)
[1]   3 100       # wrong result
> f = function(DT) {
+  for (i in 1:200) {
+    DT[,paste0("new",i):=1:3]
+  }
+  DT                            # needed in this case
+ }
> x = f(x)                       # x= needed in this case
> dim(x)
[1]   3 201                      # correct result

I seem to remember there was a warning. Maybe it isn't happening in this case for some reason. Need to reinstate the warning and add a test for it.