rewrite [trunc_add_half_ulp_eq_of_no_uflow npos no_uflow]
case inr
n x : ℕ
round : ℕ → ℕ
npos : 0 < n
hcorrect₀ : correct₀ n round
hlo : round x = trunc n x
no_uflow : x ≥ 2 ^ n
⊢ 2 * x ≤ 2 * (trunc n x + ulp n x / 2)
case inr
n x : ℕ
round : ℕ → ℕ
npos : 0 < n
hcorrect₀ : correct₀ n round
hlo : round x = trunc n x
no_uflow : x ≥ 2 ^ n
⊢ 2 * x ≤ trunc n x + next n (trunc n x)