/-- The **Minkowski Convex Body Theorem for compact domain**. If `s` is a convex compact symmetric
domain of `E` whose volume is large enough compared to the covolume of a lattice `L` of `E`, then it
contains a non-zero lattice point of `L`. Compared to
`exists_ne_zero_mem_lattice_of_measure_mul_two_pow_lt_measure`, this version requires in addition
that `s` is compact and `L` is discrete but provides a weaker inequality rather than a strict
inequality. -/
theorem exists_ne_zero_mem_lattice_of_measure_mul_two_pow_le_measure [NormedAddCommGroup E]
    [NormedSpace ℝ E] [BorelSpace E] [FiniteDimensional ℝ E] [Nontrivial E] [IsAddHaarMeasure μ]
    {L : AddSubgroup E} [Countable L] [DiscreteTopology L] (fund : IsAddFundamentalDomain L F μ)
    (h_symm : ∀ x ∈ s, -x ∈ s) (h_conv : Convex ℝ s) (h_cpt : IsCompact s)
    (h : μ F * 2 ^ finrank ℝ E ≤ μ s) :
    ∃ x ≠ 0, ((x : L) : E) ∈ s := by
  have h_mes : μ s ≠ 0 := by
    intro hμ
    suffices μ F = 0 from fund.measure_ne_zero (NeZero.ne μ) this
    rw [hμ, le_zero_iff, mul_eq_zero] at h
    exact h.resolve_right <| (pow_ne_zero_iff finrank_pos).mpr two_ne_zero
  have h_nemp : s.Nonempty := nonempty_of_measure_ne_zero h_mes
  let u : ℕ → ℝ≥0 := (exists_seq_strictAnti_tendsto 0).choose
  let K : ConvexBody E := ⟨s, h_conv, h_cpt, h_nemp⟩
  let S : ℕ → ConvexBody E := fun n => (1 + u n) • K
  let Z : ℕ → Set E := fun n => (S n) ∩ (L \ {0})
  -- The convex bodies `S n` have volume strictly larger than `μ s` and thus we can apply
  -- `exists_ne_zero_mem_lattice_of_measure_mul_two_pow_lt_measure` to them and obtain that
  -- `S n` contains a nonzero point of `L`. Since the intersection of the `S n` is equal to `s`,
  -- it follows that `s` contains a nonzero point of `L`.
  have h_zero : 0 ∈ K := K.zero_mem_of_symmetric h_symm
  suffices Set.Nonempty (⋂ n, Z n) by
    erw [← Set.iInter_inter, K.iInter_smul_eq_self h_zero] at this
    · obtain ⟨x, hx⟩ := this
      exact ⟨⟨x, by aesop⟩, by aesop⟩
    · exact (exists_seq_strictAnti_tendsto (0:ℝ≥0)).choose_spec.2.2
  have h_clos : IsClosed ((L : Set E) \ {0}) := by
    rsuffices ⟨U, hU⟩ : ∃ U : Set E, IsOpen U ∧  U ∩ L = {0}
    · rw [sdiff_eq_sdiff_iff_inf_eq_inf (z := U).mpr (by simp [Set.inter_comm .. ▸ hU.2, zero_mem])]
      exact AddSubgroup.isClosed_of_discrete.sdiff hU.1
    exact isOpen_inter_eq_singleton_of_mem_discrete (zero_mem L)
  refine IsCompact.nonempty_iInter_of_sequence_nonempty_compact_closed Z (fun n => ?_)
    (fun n => ?_) ((S 0).isCompact.inter_right h_clos) (fun n => (S n).isClosed.inter h_clos)
  · refine Set.inter_subset_inter_left _ (SetLike.coe_subset_coe.mpr ?_)
    refine ConvexBody.smul_le_of_le K h_zero ?_
    

Proof state:
case refine_1
E : Type u_1
L✝ : Type u_2
inst✝⁸ : MeasurableSpace E
μ : Measure E
F s : Set E
inst✝⁷ : NormedAddCommGroup E
inst✝⁶ : NormedSpace ℝ E
inst✝⁵ : BorelSpace E
inst✝⁴ : FiniteDimensional ℝ E
inst✝³ : Nontrivial E
inst✝² : IsAddHaarMeasure μ
L : AddSubgroup E
inst✝¹ : Countable ↥L
inst✝ : DiscreteTopology ↥L
fund : IsAddFundamentalDomain (↥L) F
h_symm : ∀ x ∈ s, -x ∈ s
h_conv : Convex ℝ s
h_cpt : IsCompact s
h : ↑↑μ F * 2 ^ finrank ℝ E ≤ ↑↑μ s
h_mes : ↑↑μ s ≠ 0
h_nemp : Set.Nonempty s
u : ℕ → ℝ≥0 := Exists.choose (_ : ∃ u, StrictAnti u ∧ (∀ (n : ℕ), 0 < u n) ∧ Tendsto u atTop (nhds 0))
K : ConvexBody E := { carrier := s, convex' := h_conv, isCompact' := h_cpt, nonempty' := h_nemp }
S : ℕ → ConvexBody E := fun n => (1 + u n) • K
Z : ℕ → Set E := fun n => ↑(S n) ∩ (↑L \ {0})
h_zero : 0 ∈ K
h_clos : IsClosed (↑L \ {0})
n : ℕ
⊢ 1 + u (n + 1) ≤ 1 + u n

Next tactic:
rw [add_le_add_iff_left]