Joined Cases C-168/19 and C-169/19: Judgment of the Court (Eighth Chamber) of 30 April 2020 (requests for a preliminary ruling from the Corte dei conti — Sezione Giurisdizionale per la Regione Puglia — Italy) — HB (C-168/19), IC (C-169/19) v Istituto nazionale della previdenza sociale (Reference for a preliminary ruling — Freedom of movement for persons — Article 21 TFEU — Principle of non-discrimination on grounds of nationality — Article 18 TFEU — Convention for the avoidance of double taxation — Public sector workers — Pensioner residing in a Member State other than that paying retirement pension and who does not have the nationality of the Member State of residence — Income tax — Alleged loss of tax advantages — Alleged impediment to freedom of movement and alleged discrimination)