Fix error, also later tests assumed success

Author: MichaelChirico

inst/tests/tests.Rraw

@@ -13935,7 +13935,8 @@ test(1967.42, x[3, rollends = rep(TRUE, 10L)], error = 'rollends must be length
 test(1967.43, x[ , ..], error = 'symbol .. is invalid')
 test(1967.44, x[NULL], data.table(NULL))
 test(1967.45, x[ , NULL], NULL)
-test(1967.46, x[ , 'b' := 6:10, with=FALSE], error='with=FALSE ignored')
+test(1967.46, x[ , 'b' := 6:10, with=FALSE], error='with=FALSE together with :=')
+x[, b := 6:10]
 test(1967.47, x[ , -1L, with = FALSE], data.table(b = 6:10))
 test(1967.48, x[ , b, .SDcols = 'a'], 6:10,
      warning = "This j doesn't use .SD")