@@ -29,23 +29,22 @@ variable (S : Subalgebra R A)
2929
3030variable {ι : Type *} [Nonempty ι] {K : ι → Subalgebra R A}
3131
32- theorem coe_iSup_of_directed (dir : Directed (· ≤ ·) K) : ↑(iSup K) = ⋃ i, (K i : Set A) :=
32+ theorem coe_iSup_of_directed (dir : Directed (· ≤ ·) K) : ↑(iSup K) = ⋃ i, (K i : Set A) := by
3333 let s : Subalgebra R A :=
3434 { __ := Subsemiring.copy _ _ (Subsemiring.coe_iSup_of_directed dir).symm
3535 algebraMap_mem' := fun _ ↦ Set.mem_iUnion.2
3636 ⟨Classical.arbitrary ι, Subalgebra.algebraMap_mem _ _⟩ }
3737 have : iSup K = s := le_antisymm
3838 (iSup_le fun i ↦ le_iSup (fun i ↦ (K i : Set A)) i) (Set.iUnion_subset fun _ ↦ le_iSup K _)
39- this.symm ▸ rfl
39+ simp [ this, s]
4040
4141variable (K)
4242
4343/-- Define an algebra homomorphism on a directed supremum of subalgebras by defining
4444it on each subalgebra, and proving that it agrees on the intersection of subalgebras. -/
4545noncomputable def iSupLift (dir : Directed (· ≤ ·) K) (f : ∀ i, K i →ₐ[R] B)
4646 (hf : ∀ (i j : ι) (h : K i ≤ K j), f i = (f j).comp (inclusion h))
47- (T : Subalgebra R A) (hT : T ≤ iSup K) : ↥T →ₐ[R] B :=
48- by
47+ (T : Subalgebra R A) (hT : T ≤ iSup K) : ↥T →ₐ[R] B := by
4948 let compat :
5049 ∀ (i j) (x : A) (hxi : x ∈ (K i : Set A)) (hxj : x ∈ (K j : Set A)),
5150 f i ⟨x, hxi⟩ = f j ⟨x, hxj⟩ := by
@@ -85,7 +84,7 @@ theorem iSupLift_inclusion {dir : Directed (· ≤ ·) K} {f : ∀ i, K i →ₐ
8584 iSupLift K dir f hf T hT (inclusion h x) = f i x := by
8685 dsimp [iSupLift, inclusion]
8786 rw [Set.iUnionLift_inclusion]
88- exact SetLike.coe_subset_coe.mpr fun ⦃x⦄ a ↦ hT (h a)
87+ exact SetLike.coe_subset_coe.mpr <| h.trans hT
8988
9089@[simp]
9190theorem iSupLift_comp_inclusion {dir : Directed (· ≤ ·) K} {f : ∀ i, K i →ₐ[R] B}
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