`expand_` not returning expected results

[markriseley]

The regular evaluation expand_ doesn't produce the same output as nse expand for what I am expecting to be exactly the same query.

Minimal example + output from R console:

expand(mtcars, vs, cyl)
#>  vs cyl
#> 1  0   4
#> 2  0   6
#> 3  0   8
#> 4  1   4
#> 5  1   6
#> 6  1   8

expand_(mtcars, dots = c("vs", "cyl"))
#> Var32 Var31 Var30 Var29 Var28 Var27 Var26 Var25 Var24 Var23 Var22 Var21 Var20 Var19
#> 1     0     0     1     1     0     1     0     1     1     1     1     0     0     0
#> Var18 Var17 Var16 Var15 Var14 Var13 Var12 Var11 Var10 Var9 Var8 Var7 Var6 Var5 Var4
#> 1     0     0     0     1     1     1     1     0     0    0    0    1    0    1    0
#> Var3 Var2 Var1
#> 1    0    0    1


devtools::session_info()
Session info --------------------------------------------------------------------------
 setting  value                       
 version  R version 3.1.2 (2014-10-31)
 system   x86_64, mingw32             
 ui       RStudio (0.99.283)          
 language (EN)                        
 collate  English_United Kingdom.1252 
 tz       Europe/London               

Packages ------------------------------------------------------------------------------
 package    * version     date       source                          
 devtools   * 1.7.0       2015-01-17 CRAN (R 3.1.2)                  
 lazyeval   * 0.1.10.9000 2015-02-24 Github (hadley/lazyeval@08f5900)
 rstudioapi * 0.2         2014-12-31 CRAN (R 3.1.2)                  
 tidyr        0.2.0.9000  2015-03-30 Github (hadley/tidyr@3de52c4)