⟧.own([x]) ∗ ⟦rc τ ⟧.own([y])} x.cnt += 1; ? x.cnt += 1; let y = ptr::read(x) Goal Proof sketch {∃ℓ.?=ℓ∗∃?∈ℤ+¿,?∈ℚ∩¿.¿ℓ↦[?+1]++[?]∗sharedown(?,ℓ,?,?,?)} ? Rc::::clone Examples ? ℓ ↦[?+1]++[ ’∈ℚ∩¿.¿ℓ↦[?’]++[?]∗sharedown(?,ℓ,?,?’,?’)∗ ℓ↦[?’]++[?]∗sharedown(?,ℓ ,? ,?’,?’) } ?’ ?’ Proof sketch ⟦rc τ ⟧.own([x]) ⟦rc τ ⟧.own([y]) Q.E.D. {⋯} let y = ptr::read(x) Thank you ！