`shift` crashes R when using `n = "lead"`

While I'm aware this is incorrect use of the shift function, but if you forget to specify the type argument and use shift(val, "lead"), this causes Rstudio to crash.

Reproducible example

library(data.table)

dt <- data.table(
  id = 1:5
  , val = letters[1:5]
)

## This will crash RStudio
dt[, new_col := shift(val, "lead")]

## the fix is to specify `type = "lead"`
dt[, new_col := shift(val, type = "lead")]

Session info

devtools::session_info()
─ Session info ────────────────────────────────────────────────────────────────────────────────────────────
 setting  value                       
 version  R version 3.5.1 (2018-07-02)
 os       macOS  10.14.1              
 system   x86_64, darwin15.6.0        
 ui       RStudio                     
 language (EN)                        
 collate  en_AU.UTF-8                 
 ctype    en_AU.UTF-8                 
 tz       Australia/Melbourne         
 date     2019-02-05                  

─ Packages ────────────────────────────────────────────────────────────────────────────────────────────────
 ! package     * version date       lib source                                
   assertthat    0.2.0   2017-04-11 [2] CRAN (R 3.5.0)                        
   backports     1.1.2   2017-12-13 [2] CRAN (R 3.5.0)                        
   callr         2.0.3   2018-04-11 [2] CRAN (R 3.5.0)                        
   cli           1.0.1   2018-09-25 [1] CRAN (R 3.5.0)                        
   crayon        1.3.4   2017-09-16 [2] CRAN (R 3.5.0)                        
   curl          3.3     2019-01-10 [1] CRAN (R 3.5.2)                        
 V data.table  * 1.12.0  2019-02-05 [1] Github (Rdatatable/data.table@e043dd2)
   debugme       1.1.0   2017-10-22 [2] CRAN (R 3.5.0)                        
   desc          1.2.0   2018-05-01 [2] CRAN (R 3.5.0)                        
   devtools      2.0.1   2018-10-26 [1] CRAN (R 3.5.0)                        
   digest        0.6.18  2018-10-10 [1] CRAN (R 3.5.0)                        
   fs            1.2.6   2018-08-23 [1] CRAN (R 3.5.0)                        
   glue          1.3.0   2018-07-17 [2] CRAN (R 3.5.0)                        
   magrittr      1.5     2014-11-22 [2] CRAN (R 3.5.0)                        
   memoise       1.1.0   2017-04-21 [2] CRAN (R 3.5.0)                        
   pkgbuild      1.0.2   2018-10-16 [1] CRAN (R 3.5.0)                        
   pkgload       1.0.2   2018-10-29 [1] CRAN (R 3.5.0)                        
   prettyunits   1.0.2   2015-07-13 [2] CRAN (R 3.5.0)                        
   R6            2.3.0   2018-10-04 [1] CRAN (R 3.5.0)                        
   Rcpp          1.0.0   2018-11-07 [1] CRAN (R 3.5.0)                        
   remotes       2.0.2   2018-10-30 [1] CRAN (R 3.5.0)                        
   rlang         0.3.1   2019-01-08 [1] CRAN (R 3.5.2)                        
   rprojroot     1.3-2   2018-01-03 [2] CRAN (R 3.5.0)                        
   rstudioapi    0.8     2018-10-02 [1] CRAN (R 3.5.0)                        
   sessioninfo   1.1.0   2018-09-25 [1] CRAN (R 3.5.0)                        
   testthat      2.0.0   2017-12-13 [2] CRAN (R 3.5.0)                        
   usethis       1.4.0   2018-08-14 [1] CRAN (R 3.5.0)                        
   withr         2.1.2   2018-03-15 [2] CRAN (R 3.5.0)                        

[1] /Users/david/Library/R/3.5/library
[2] /Library/Frameworks/R.framework/Versions/3.5/Resources/library

 V ── Loaded and on-disk version mismatch.

[jangorecki]

@SymbolixAU could you also provide utils::sessionInfo() output? The above one looks corrupted at first glance:

data.table * 1.12.0 2019-02-05 [1] Github (Rdatatable/data.table@e043dd2)

e043dd2 is not 1.12.0 but 1.12.1

@jangorecki sure thing

This is the sessioninfo() when I ran the original code

utils::sessionInfo()
R version 3.5.1 (2018-07-02)
Platform: x86_64-apple-darwin15.6.0 (64-bit)
Running under: macOS  10.14.1

Matrix products: default
BLAS: /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib
LAPACK: /Library/Frameworks/R.framework/Versions/3.5/Resources/lib/libRlapack.dylib

locale:
[1] en_AU.UTF-8/en_AU.UTF-8/en_AU.UTF-8/C/en_AU.UTF-8/en_AU.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] data.table_1.12.1    microbenchmark_1.4-4

loaded via a namespace (and not attached):
[1] compiler_3.5.1 tools_3.5.1 

---

I've updated to the latest release and get the same error

remove.packages("data.table")
install.packages("data.table", type = "source",
                 repos = "http://Rdatatable.github.io/data.table")

library(data.table)

dt <- data.table(
  id = 1:5
  , val = letters[1:5]
)

## This will crash RStudio
dt[, new_col := shift(val, "lead")]

devtools::session_info(pkgs = "data.table")
─ Session info ─────────────────────────────────────────────────────────────────────────────────────────────────────────────
 setting  value                       
 version  R version 3.5.1 (2018-07-02)
 os       macOS  10.14.1              
 system   x86_64, darwin15.6.0        
 ui       RStudio                     
 language (EN)                        
 collate  en_AU.UTF-8                 
 ctype    en_AU.UTF-8                 
 tz       Australia/Melbourne         
 date     2019-02-06                  

─ Packages ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────
 package    * version date       lib source
 data.table * 1.12.1  2019-02-05 [1] local 

[1] /Users/david/Library/R/3.5/library
[2] /Library/Frameworks/R.framework/Versions/3.5/Resources/library