message: Be more conservative, still track external fields
diff: @@ -287,7 +287,8 @@ class Analyzer final : public BaseIRAnalyzer<CseEnvironment> {
  // If we are reading a final field...
  if (location.has_field() && is_final(location.get_field()) &&
  !root(location.get_field()) && can_rename(location.get_field()) &&
  - can_delete(location.get_field())) {
  + can_delete(location.get_field()) &&
  + !location.get_field()->is_external()) {
  // ... and we are not analyzing a method that is a corresponding
  // constructor or static initializer of the declaring type of the
  // field ...
  