code: func Sourceless(severity Severity, summary, detail string) Diagnostic {
  	return diagnosticBase{
  		severity: severity,
  		summary:  summary,
  		detail:   detail,
  	}
  }
docs: // Sourceless creates and returns a diagnostic with no source location
  // information. This is generally used for operational-type errors that are
  // caused by or relate to the environment where Terraform is running rather
  // than to the provided configuration.