code: private SoyMsgPart compactPart(SoyMsgPart part) {
      if (part instanceof SoyMsgPluralPart) {
        part = compactPlural((SoyMsgPluralPart) part);
      } else if (part instanceof SoyMsgSelectPart) {
        part = compactSelect((SoyMsgSelectPart) part);
      } else if (part instanceof SoyMsgPlaceholderPart) {
        part = compactPlaceholder((SoyMsgPlaceholderPart) part);
      }
      // Now intern the message part.
      return intern(part);
    }
docs: Compacts a single message part.
  
  <p>If the part is a plural/select part, it might be expanded into multiple parts.