> rownames_to_column(mtcars, "cyl")
Error: Column name `cyl` must not be duplicated.

> rowid_to_column(iris, "Species")
Error: Column name `Species` must not be duplicated.

> column_to_rownames(mtcars, "cyl")
Error: `.data` must be a data frame without row names.

> column_to_rownames(iris, "foo")
Error: Can't find column `foo` in `.data`.

