Figuring out the right damages measure for default on an actively traded financial asset such as a government bond is, at first, obvious -- just pay what you promised on the bond.  But then, when one thinks about features of damages law such as the option to substitute performance or mitigation, things get murkier.

Citation
G. Mitu Gulati, Yehuda Adar on Contract Damages -- In a Bond Default, Credit Slips (2022).