to_null.md
In stbl: Stabilize Function Arguments

to_null() errors when NULL isn't allowed

Code
  to_null(given, allow_null = FALSE)
Condition
  Error:
  ! `given` must not be <NULL>.

Code
  wrapper(given, allow_null = FALSE)
Condition
  Error in `wrapper()`:
  ! `wrapper_val` must not be <NULL>.

to_null() errors informatively for weird allow_null values

Code
  to_null(NULL, allow_null = NULL)
Condition
  Error:
  ! `allow_null` must not be <NULL>.

Code
  to_null(NULL, allow_null = "fish")
Condition
  Error:
  ! `allow_null` <character> must be coercible to <logical>
  x Can't convert some values due to incompatible values.
  * Locations: 1

Code
  wrapper(given, allow_null = NULL)
Condition
  Error in `wrapper()`:
  ! `allow_null` must not be <NULL>.

Code
  wrapper(given, allow_null = "fish")
Condition
  Error in `wrapper()`:
  ! `allow_null` <character> must be coercible to <logical>
  x Can't convert some values due to incompatible values.
  * Locations: 1