unit tests for #3779 (#4576)

Author: jangorecki

inst/tests/tests.Rraw

@@ -17709,10 +17709,15 @@ test(2191, DT[1:5, sum(v), by=.(i5 = 1:5 %% 2L), verbose=TRUE], data.table(i5=1:
 test(2192.1, as.IDate(c('', '2020-01-01')), structure(c(NA_integer_, 18262L), class=c("IDate","Date")))
 test(2192.2, as.IDate(c('2020-01-01', '')), structure(c(18262L, NA_integer_), class=c("IDate","Date")))
 
-# subassign coerce to integer64 was fixed in 1.12.4, #2530
 if (test_bit64) {
+  # subassign coerce to integer64 was fixed in 1.12.4, #2530
   DT = data.table(a = as.integer64(1:10))
   DT[a==1, a:=12]
   DT[a==2, a:=as.integer64(13)]
-  test(2193, DT, data.table(a = as.integer64(c(12,13,3:10))))
+  test(2193.1, DT, data.table(a = as.integer64(c(12,13,3:10))))
+  
+  # X[Y,,by=.EACHI] when Y contains integer64 also fixed in 1.12.4, #3779
+  X = data.table(x=1:3)
+  Y = data.table(x=1:2, y=as.integer64(c(10,20)))
+  test(2193.2, X[Y, `:=`(y=i.y), on="x", by=.EACHI], data.table(x=1:3, y=as.integer64(10L,20L,NA)))
 }