I was honestly hoping that since the fix was simple enough, someone would be able to incorporate it easily. I'm not aware of any way to workaround it at this point besides writing it in another language since the issue is in the test harness.

Swift version won't pass even when test cases are satisfied because of warnings in the test harness writing to stderr.

main.swift:20:17: warning: initialization of immutable value 'ans' was never used; consider replacing with assignment to '_' or removing it

let ans = try assemblerInterpreter(exampleErrorProgram)

A simple assignment to '_' would suffice for swift 3.

For swift 4 an additional warning is output to stderr:

main.swift:197:32: warning: 'characters' is deprecated: Please use String or Substring directly

let code = rawCode.characters.map { String($0) }