git-issue-4946c.dfy(6,5): Error: cannot find witness that shows type is inhabited; try giving a hint through a 'witness' or 'ghost witness' clause, or use 'witness *' to treat as a possibly empty type
git-issue-4946c.dfy(7,5): Error: trying witness null: value of expression (of type 'ReferenceTrait?') is not known to be an instance of type 'ReferenceTrait', because it might be null

Dafny program verifier finished with 0 verified, 2 errors
