> vars_pull(letters, letters)
Error: Must extract column with a single subscript.
x The subscript `var` has size 26 but must be size 1.

> vars_pull(letters, aa)
Error: object 'aa' not found

> vars_pull(letters, 0)
Error: Must extract column with a single subscript.
x The subscript `var` has value 0 but must be a positive location.

> vars_pull(letters, 100)
Error: Can't extract columns that don't exist.
x The location 100 doesn't exist.
i There are only 26 columns.

> vars_pull(letters, -100)
Error: Can't extract columns that don't exist.
x The location 100 doesn't exist.
i There are only 26 columns.

> vars_pull(letters, -Inf)
Error: Must extract column with a single subscript.
x Lossy cast from `var` <double> to <integer>.

> vars_pull(letters, TRUE)
Error: Must extract column with a single subscript.
x The subscript `var` has the wrong type `logical`.
i It must be numeric or character.

> vars_pull(letters, NA)
Error: Must extract column with a single subscript.
x The subscript `var` can't be `NA`.

> vars_pull(letters, na_int)
Error: Must extract column with a single subscript.
x The subscript `var` can't be `NA`.

> vars_pull(letters, "foo")
Error: Can't extract columns that don't exist.
x The column `foo` doesn't exist.

> vars_pull(letters, !!c("a", "b"))
Error: Must extract column with a single subscript.
x The subscript `var` has size 2 but must be size 1.

