Why does Term::map_from_pairs return a NifResult?

[radrow]

I don't understand the circumstances in which it fails. Creating a new map is safe, so should be inserting to something we know is a map. Am I missing something?

[filmor]

It fails on duplicate keys.

[radrow]

Why though? It's the first time I see this considered to be a reason to fail to be honest. Also, Erlang does not crash if you do it.

[filmor]

The function just fails, nothing crashes. See https://www.erlang.org/doc/man/erl_nif.html#enif_make_map_from_arrays, which is the underlying function that is exposed here.