IO Concepting

• requires builtin or standard error type, and error list type
• Builtin types:
  • part of environment bringup?
  • standard newt files
• no code generation/preprocessing
• validate similarily to for/if/while loops
• can't return anything from a using block except an error--is this a problem?
  • premature termination--file contents not what we want?
  • allow inferred return types?
• I/O classes must be defensively designed to handle escaping references to closed files/de-allocated resources
• resource requires statefulness, i.e objects?
  • function that returns stream state object?

using := (resource:__, handler:(__) -> errors) -> errors {
	errors = resource.setup()
	if (errors == @errors) {
		handler_errors := handler(resource)
		return handler_errors.concatenate(resource.teardown())
	}

	return errors
}

res := using file_handle('tmp.txt', 'rb') as input_file -> {
	for line in input_file.read_line() {
		print(line)
	}

	subject = input_file.read_line()
	while(subject != nil) {
		print(subject.value)
		subject = subject.next
	}
}