dplyr::row_number get error inside mutate

[italocegatta]

If I use row_number() works well, but if I call dplyr::row_number() returns an error

library(dplyr)

packageVersion("dplyr")
#> [1] '0.7.2'

iris <- head(iris)

mutate(iris, id = row_number())
#>   Sepal.Length Sepal.Width Petal.Length Petal.Width Species id
#> 1          5.1         3.5          1.4         0.2  setosa  1
#> 2          4.9         3.0          1.4         0.2  setosa  2
#> 3          4.7         3.2          1.3         0.2  setosa  3
#> 4          4.6         3.1          1.5         0.2  setosa  4
#> 5          5.0         3.6          1.4         0.2  setosa  5
#> 6          5.4         3.9          1.7         0.4  setosa  6

mutate(iris, id = dplyr::row_number())
#> Error in mutate_impl(.data, dots) : 
#>   Evaluation error: argument "x" is missing, with no default.

[foo-bar-baz-qux]

I don't think row_number() without any ordering parameter has a consistent interpretation in SQL/relational databases in general, and since the dplyr::row_number() is based on SQL2003, it would make sense that it returns an error.

I assume the native row_number() just returns the "original" ordering, like mutate(iris, id = 1:NROW(iris)), but if anything, it seems like this native version should in fact return an error if dplyr is based on a SQL style interface.