Weird `add_constr_custom()` behaviors

[christopherkenny]

• [ ] If a call to a function is present using ::, you get the following warning.

  Error in `rlang::as_string()`:
  ! Can't convert a call to a string.

  Workaround: Define the required function in the global environment before using it, like colMins <- matrixStats::colMins before declaring the custom constraint.

• [ ] Sub-redist_maps after filtering fail if you rely on the district number and the numbers are not sequential. On an example Iowa map, filter out district 2 and then try to subset to access district 2, causing a NaN issue. Workaround: renumber the existing_col when you create the map

[christopherkenny]

:: issue fixed by explicitly using a child environment. That's wrong, still broken.

[CoryMcCartan]

Can you elaborate on the 2nd issue?

Shouldn't accessing indices that don't exist cause problems?