I noticed when hacking on lix's JSON parser that it silently accepts duplicate json object keys, throwing away all but the last one. Is this known and desired behavior? I tried making it crash instead and it seemed to still pass all of the tests, so this behavior isn't being tested for.
nix eval --expr 'builtins.fromJSON '"''"'{"a":"a","a":"b"}'"''"

{ a = "b"; }