group_theory.nielsen_schreier ⟷ Mathlib.GroupTheory.FreeGroup.NielsenSchreier

mathlib commit https://github.com/leanprover-community/mathlib/commit/65a1391a0106c9204fe45bc73a039f056558cb83

@@ -6,7 +6,7 @@ Authors: David Wärn
 import CategoryTheory.Action
 import Combinatorics.Quiver.Arborescence
 import Combinatorics.Quiver.ConnectedComponent
-import GroupTheory.IsFreeGroup
+import GroupTheory.FreeGroup.IsFreeGroup
 
 #align_import group_theory.nielsen_schreier from "leanprover-community/mathlib"@"2ed2c6310e6f1c5562bdf6bfbda55ebbf6891abe"
 
@@ -202,7 +202,7 @@ def loopOfHom {a b : G} (p : a ⟶ b) : End (root' T) :=
 #align is_free_groupoid.spanning_tree.loop_of_hom IsFreeGroupoid.SpanningTree.loopOfHom
 -/
 
-/- ./././Mathport/Syntax/Translate/Basic.lean:641:2: warning: expanding binder collection (e «expr ∈ » wide_subquiver_symmetrify[quiver.wide_subquiver_symmetrify] T a b) -/
+/- ./././Mathport/Syntax/Translate/Basic.lean:642:2: warning: expanding binder collection (e «expr ∈ » wide_subquiver_symmetrify[quiver.wide_subquiver_symmetrify] T a b) -/
 #print IsFreeGroupoid.SpanningTree.loopOfHom_eq_id /-
 /-- Turning an edge in the spanning tree into a loop gives the indentity loop. -/
 theorem loopOfHom_eq_id {a b : Generators G} (e) (_ : e ∈ wideSubquiverSymmetrify T a b) :

mathlib commit https://github.com/leanprover-community/mathlib/commit/65a1391a0106c9204fe45bc73a039f056558cb83

@@ -309,7 +309,7 @@ theorem path_nonempty_of_hom {G} [Groupoid.{u, u} G] [IsFreeGroupoid G] {a b : G
 /-- Given a connected free groupoid, its generating quiver is rooted-connected. -/
 instance generators_connected (G) [Groupoid.{u, u} G] [IsConnected G] [IsFreeGroupoid G] (r : G) :
     RootedConnected (symgen r) :=
-  ⟨fun b => path_nonempty_of_hom (CategoryTheory.nonempty_hom_of_connected_groupoid r b)⟩
+  ⟨fun b => path_nonempty_of_hom (CategoryTheory.nonempty_hom_of_preconnected_groupoid r b)⟩
 #align is_free_groupoid.generators_connected IsFreeGroupoid.generators_connected
 -/
 

mathlib commit https://github.com/leanprover-community/mathlib/commit/3365b20c2ffa7c35e47e5209b89ba9abdddf3ffe

@@ -239,7 +239,7 @@ def functorOfMonoidHom {X} [Monoid X] (f : End (root' T) →* X) : G ⥤ Categor
     group at the root is freely generated by loops coming from generating arrows
     in the complement of the tree. -/
 def endIsFree : IsFreeGroup (End (root' T)) :=
-  IsFreeGroup.ofUniqueLift ((wideSubquiverEquivSetTotal <| wideSubquiverSymmetrify T)ᶜ : Set _)
+  IsFreeGroup.of_unique_lift ((wideSubquiverEquivSetTotal <| wideSubquiverSymmetrify T)ᶜ : Set _)
     (fun e => loopOfHom T (of e.val.Hom))
     (by
       intro X _ f
@@ -328,7 +328,7 @@ end IsFreeGroupoid
 /-- The Nielsen-Schreier theorem: a subgroup of a free group is free. -/
 instance subgroupIsFreeOfIsFree {G : Type u} [Group G] [IsFreeGroup G] (H : Subgroup G) :
     IsFreeGroup H :=
-  IsFreeGroup.ofMulEquiv (endMulEquivSubgroup H)
+  IsFreeGroup.of_mulEquiv (endMulEquivSubgroup H)
 #align subgroup_is_free_of_is_free subgroupIsFreeOfIsFree
 -/
 

mathlib commit https://github.com/leanprover-community/mathlib/commit/ce64cd319bb6b3e82f31c2d38e79080d377be451

@@ -3,10 +3,10 @@ Copyright (c) 2021 David Wärn. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: David Wärn
 -/
-import Mathbin.CategoryTheory.Action
-import Mathbin.Combinatorics.Quiver.Arborescence
-import Mathbin.Combinatorics.Quiver.ConnectedComponent
-import Mathbin.GroupTheory.IsFreeGroup
+import CategoryTheory.Action
+import Combinatorics.Quiver.Arborescence
+import Combinatorics.Quiver.ConnectedComponent
+import GroupTheory.IsFreeGroup
 
 #align_import group_theory.nielsen_schreier from "leanprover-community/mathlib"@"2ed2c6310e6f1c5562bdf6bfbda55ebbf6891abe"
 
@@ -202,7 +202,7 @@ def loopOfHom {a b : G} (p : a ⟶ b) : End (root' T) :=
 #align is_free_groupoid.spanning_tree.loop_of_hom IsFreeGroupoid.SpanningTree.loopOfHom
 -/
 
-/- ./././Mathport/Syntax/Translate/Basic.lean:635:2: warning: expanding binder collection (e «expr ∈ » wide_subquiver_symmetrify[quiver.wide_subquiver_symmetrify] T a b) -/
+/- ./././Mathport/Syntax/Translate/Basic.lean:641:2: warning: expanding binder collection (e «expr ∈ » wide_subquiver_symmetrify[quiver.wide_subquiver_symmetrify] T a b) -/
 #print IsFreeGroupoid.SpanningTree.loopOfHom_eq_id /-
 /-- Turning an edge in the spanning tree into a loop gives the indentity loop. -/
 theorem loopOfHom_eq_id {a b : Generators G} (e) (_ : e ∈ wideSubquiverSymmetrify T a b) :

mathlib commit https://github.com/leanprover-community/mathlib/commit/8ea5598db6caeddde6cb734aa179cc2408dbd345

@@ -2,17 +2,14 @@
 Copyright (c) 2021 David Wärn. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: David Wärn
-
-! This file was ported from Lean 3 source module group_theory.nielsen_schreier
-! leanprover-community/mathlib commit 2ed2c6310e6f1c5562bdf6bfbda55ebbf6891abe
-! Please do not edit these lines, except to modify the commit id
-! if you have ported upstream changes.
 -/
 import Mathbin.CategoryTheory.Action
 import Mathbin.Combinatorics.Quiver.Arborescence
 import Mathbin.Combinatorics.Quiver.ConnectedComponent
 import Mathbin.GroupTheory.IsFreeGroup
 
+#align_import group_theory.nielsen_schreier from "leanprover-community/mathlib"@"2ed2c6310e6f1c5562bdf6bfbda55ebbf6891abe"
+
 /-!
 # The Nielsen-Schreier theorem
 
@@ -205,7 +202,7 @@ def loopOfHom {a b : G} (p : a ⟶ b) : End (root' T) :=
 #align is_free_groupoid.spanning_tree.loop_of_hom IsFreeGroupoid.SpanningTree.loopOfHom
 -/
 
-/- ./././Mathport/Syntax/Translate/Basic.lean:638:2: warning: expanding binder collection (e «expr ∈ » wide_subquiver_symmetrify[quiver.wide_subquiver_symmetrify] T a b) -/
+/- ./././Mathport/Syntax/Translate/Basic.lean:635:2: warning: expanding binder collection (e «expr ∈ » wide_subquiver_symmetrify[quiver.wide_subquiver_symmetrify] T a b) -/
 #print IsFreeGroupoid.SpanningTree.loopOfHom_eq_id /-
 /-- Turning an edge in the spanning tree into a loop gives the indentity loop. -/
 theorem loopOfHom_eq_id {a b : Generators G} (e) (_ : e ∈ wideSubquiverSymmetrify T a b) :

mathlib commit https://github.com/leanprover-community/mathlib/commit/9fb8964792b4237dac6200193a0d533f1b3f7423

@@ -97,6 +97,7 @@ namespace IsFreeGroupoid
 
 attribute [instance] quiver_generators
 
+#print IsFreeGroupoid.ext_functor /-
 /-- Two functors from a free groupoid to a group are equal when they agree on the generating
 quiver. -/
 @[ext]
@@ -106,6 +107,7 @@ theorem ext_functor {G} [Groupoid.{v} G] [IsFreeGroupoid G] {X : Type v} [Group
   let ⟨_, _, u⟩ := @unique_lift G _ _ X _ fun (a b : Generators G) (e : a ⟶ b) => g.map (of e)
   trans (u _ h) (u _ fun _ _ _ => rfl).symm
 #align is_free_groupoid.ext_functor IsFreeGroupoid.ext_functor
+-/
 
 #print IsFreeGroupoid.actionGroupoidIsFree /-
 /-- An action groupoid over a free group is free. More generally, one could show that the groupoid
@@ -325,9 +327,11 @@ instance endIsFreeOfConnectedFree {G} [Groupoid G] [IsConnected G] [IsFreeGroupo
 
 end IsFreeGroupoid
 
+#print subgroupIsFreeOfIsFree /-
 /-- The Nielsen-Schreier theorem: a subgroup of a free group is free. -/
 instance subgroupIsFreeOfIsFree {G : Type u} [Group G] [IsFreeGroup G] (H : Subgroup G) :
     IsFreeGroup H :=
   IsFreeGroup.ofMulEquiv (endMulEquivSubgroup H)
 #align subgroup_is_free_of_is_free subgroupIsFreeOfIsFree
+-/
 

mathlib commit https://github.com/leanprover-community/mathlib/commit/31c24aa72e7b3e5ed97a8412470e904f82b81004

@@ -203,7 +203,7 @@ def loopOfHom {a b : G} (p : a ⟶ b) : End (root' T) :=
 #align is_free_groupoid.spanning_tree.loop_of_hom IsFreeGroupoid.SpanningTree.loopOfHom
 -/
 
-/- ./././Mathport/Syntax/Translate/Basic.lean:635:2: warning: expanding binder collection (e «expr ∈ » wide_subquiver_symmetrify[quiver.wide_subquiver_symmetrify] T a b) -/
+/- ./././Mathport/Syntax/Translate/Basic.lean:638:2: warning: expanding binder collection (e «expr ∈ » wide_subquiver_symmetrify[quiver.wide_subquiver_symmetrify] T a b) -/
 #print IsFreeGroupoid.SpanningTree.loopOfHom_eq_id /-
 /-- Turning an edge in the spanning tree into a loop gives the indentity loop. -/
 theorem loopOfHom_eq_id {a b : Generators G} (e) (_ : e ∈ wideSubquiverSymmetrify T a b) :

mathlib commit https://github.com/leanprover-community/mathlib/commit/5f25c089cb34db4db112556f23c50d12da81b297

@@ -62,7 +62,7 @@ open scoped Classical
 
 universe v u
 
-/- ./././Mathport/Syntax/Translate/Command.lean:229:11: unsupported: unusual advanced open style -/
+/- ./././Mathport/Syntax/Translate/Command.lean:230:11: unsupported: unusual advanced open style -/
 open CategoryTheory CategoryTheory.ActionCategory CategoryTheory.SingleObj Quiver
 
 #print IsFreeGroupoid.Generators /-

mathlib commit https://github.com/leanprover-community/mathlib/commit/cca40788df1b8755d5baf17ab2f27dacc2e17acb

@@ -144,7 +144,7 @@ instance actionGroupoidIsFree {G A : Type u} [Group G] [IsFreeGroup G] [MulActio
         · convert hE _ _ _; rfl
         · rfl
       apply functor.hext
-      · intro ; apply Unit.ext
+      · intro; apply Unit.ext
       · refine' action_category.cases _; intros
         simp only [← this, uncurry_map, curry_apply_left, coe_back, hom_of_pair.val]
 #align is_free_groupoid.action_groupoid_is_free IsFreeGroupoid.actionGroupoidIsFree
@@ -298,7 +298,7 @@ theorem path_nonempty_of_hom {G} [Groupoid.{u, u} G] [IsFreeGroupoid G] {a b : G
   let f : G → X := fun g => FreeGroup.of (weakly_connected_component.mk g)
   let F : G ⥤ CategoryTheory.SingleObj X := single_obj.difference_functor f
   change F.map p = ((CategoryTheory.Functor.const G).obj ()).map p
-  congr ; ext
+  congr; ext
   rw [functor.const_obj_map, id_as_one, difference_functor_map, mul_inv_eq_one]
   apply congr_arg FreeGroup.of
   apply (weakly_connected_component.eq _ _).mpr

mathlib commit https://github.com/leanprover-community/mathlib/commit/917c3c072e487b3cccdbfeff17e75b40e45f66cb

@@ -58,7 +58,7 @@ free group, free groupoid, Nielsen-Schreier
 
 noncomputable section
 
-open Classical
+open scoped Classical
 
 universe v u
 

mathlib commit https://github.com/leanprover-community/mathlib/commit/917c3c072e487b3cccdbfeff17e75b40e45f66cb

@@ -97,12 +97,6 @@ namespace IsFreeGroupoid
 
 attribute [instance] quiver_generators
 
-/- warning: is_free_groupoid.ext_functor -> IsFreeGroupoid.ext_functor is a dubious translation:
-lean 3 declaration is
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-but is expected to have type
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-Case conversion may be inaccurate. Consider using '#align is_free_groupoid.ext_functor IsFreeGroupoid.ext_functorₓ'. -/
 /-- Two functors from a free groupoid to a group are equal when they agree on the generating
 quiver. -/
 @[ext]
@@ -331,12 +325,6 @@ instance endIsFreeOfConnectedFree {G} [Groupoid G] [IsConnected G] [IsFreeGroupo
 
 end IsFreeGroupoid
 
-/- warning: subgroup_is_free_of_is_free -> subgroupIsFreeOfIsFree is a dubious translation:
-lean 3 declaration is
-  forall {G : Type.{u1}} [_inst_1 : Group.{u1} G] [_inst_2 : IsFreeGroup.{u1} G _inst_1] (H : Subgroup.{u1} G _inst_1), IsFreeGroup.{u1} (coeSort.{succ u1, succ (succ u1)} (Subgroup.{u1} G _inst_1) Type.{u1} (SetLike.hasCoeToSort.{u1, u1} (Subgroup.{u1} G _inst_1) G (Subgroup.setLike.{u1} G _inst_1)) H) (Subgroup.toGroup.{u1} G _inst_1 H)
-but is expected to have type
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-Case conversion may be inaccurate. Consider using '#align subgroup_is_free_of_is_free subgroupIsFreeOfIsFreeₓ'. -/
 /-- The Nielsen-Schreier theorem: a subgroup of a free group is free. -/
 instance subgroupIsFreeOfIsFree {G : Type u} [Group G] [IsFreeGroup G] (H : Subgroup G) :
     IsFreeGroup H :=

mathlib commit https://github.com/leanprover-community/mathlib/commit/917c3c072e487b3cccdbfeff17e75b40e45f66cb

@@ -147,14 +147,11 @@ instance actionGroupoidIsFree {G A : Type u} [Group G] [IsFreeGroup G] [MulActio
         apply uF'
         intro e
         ext
-        · convert hE _ _ _
-          rfl
+        · convert hE _ _ _; rfl
         · rfl
       apply functor.hext
-      · intro
-        apply Unit.ext
-      · refine' action_category.cases _
-        intros
+      · intro ; apply Unit.ext
+      · refine' action_category.cases _; intros
         simp only [← this, uncurry_map, curry_apply_left, coe_back, hom_of_pair.val]
 #align is_free_groupoid.action_groupoid_is_free IsFreeGroupoid.actionGroupoidIsFree
 -/
@@ -220,8 +217,7 @@ theorem loopOfHom_eq_id {a b : Generators G} (e) (_ : e ∈ wideSubquiverSymmetr
   by
   rw [loop_of_hom, ← category.assoc, is_iso.comp_inv_eq, category.id_comp]
   cases H
-  · rw [tree_hom_eq T (path.cons default ⟨Sum.inl e, H⟩), hom_of_path]
-    rfl
+  · rw [tree_hom_eq T (path.cons default ⟨Sum.inl e, H⟩), hom_of_path]; rfl
   · rw [tree_hom_eq T (path.cons default ⟨Sum.inr e, H⟩), hom_of_path]
     simp only [is_iso.inv_hom_id, category.comp_id, category.assoc, tree_hom]
 #align is_free_groupoid.spanning_tree.loop_of_hom_eq_id IsFreeGroupoid.SpanningTree.loopOfHom_eq_id
@@ -267,15 +263,12 @@ def endIsFree : IsFreeGroup (End (root' T)) :=
         suffices ∀ {a} (p : Path (root' T) a), F'.map (hom_of_path T p) = 1 by
           simp only [this, tree_hom, comp_as_mul, inv_as_inv, loop_of_hom, inv_one, mul_one,
             one_mul, functor.map_inv, functor.map_comp]
-        intro a p
-        induction' p with b c p e ih
+        intro a p; induction' p with b c p e ih
         · rw [hom_of_path, F'.map_id, id_as_one]
         rw [hom_of_path, F'.map_comp, comp_as_mul, ih, mul_one]
         rcases e with ⟨e | e, eT⟩
-        · rw [hF']
-          exact dif_pos (Or.inl eT)
-        · rw [F'.map_inv, inv_as_inv, inv_eq_one, hF']
-          exact dif_pos (Or.inr eT)
+        · rw [hF']; exact dif_pos (Or.inl eT)
+        · rw [F'.map_inv, inv_as_inv, inv_eq_one, hF']; exact dif_pos (Or.inr eT)
       · intro E hE
         ext
         suffices (functor_of_monoid_hom T E).map x = F'.map x by

mathlib commit https://github.com/leanprover-community/mathlib/commit/917c3c072e487b3cccdbfeff17e75b40e45f66cb

@@ -171,7 +171,6 @@ variable {G : Type u} [Groupoid.{u} G] [IsFreeGroupoid G]
 /-- The root of `T`, except its type is `G` instead of the type synonym `T`. -/
 private def root' : G :=
   show T from root T
-#align is_free_groupoid.spanning_tree.root' is_free_groupoid.spanning_tree.root'
 
 #print IsFreeGroupoid.SpanningTree.homOfPath /-
 -- this has to be marked noncomputable, see issue #451.
@@ -298,7 +297,6 @@ end SpanningTree
 private def symgen {G : Type u} [Groupoid.{v} G] [IsFreeGroupoid G] :
     G → Symmetrify (Generators G) :=
   id
-#align is_free_groupoid.symgen is_free_groupoid.symgen
 
 #print IsFreeGroupoid.path_nonempty_of_hom /-
 /-- If there exists a morphism `a → b` in a free groupoid, then there also exists a zigzag

mathlib commit https://github.com/leanprover-community/mathlib/commit/c89fe2d59ae06402c3f55f978016d1ada444f57e

@@ -4,7 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: David Wärn
 
 ! This file was ported from Lean 3 source module group_theory.nielsen_schreier
-! leanprover-community/mathlib commit 1bda4fc53de6ade5ab9da36f2192e24e2084a2ce
+! leanprover-community/mathlib commit 2ed2c6310e6f1c5562bdf6bfbda55ebbf6891abe
 ! Please do not edit these lines, except to modify the commit id
 ! if you have ported upstream changes.
 -/
@@ -16,6 +16,9 @@ import Mathbin.GroupTheory.IsFreeGroup
 /-!
 # The Nielsen-Schreier theorem
 
+> THIS FILE IS SYNCHRONIZED WITH MATHLIB4.
+> Any changes to this file require a corresponding PR to mathlib4.
+
 This file proves that a subgroup of a free group is itself free.
 
 ## Main result

mathlib commit https://github.com/leanprover-community/mathlib/commit/7ad820c4997738e2f542f8a20f32911f52020e26

@@ -62,6 +62,7 @@ universe v u
 /- ./././Mathport/Syntax/Translate/Command.lean:229:11: unsupported: unusual advanced open style -/
 open CategoryTheory CategoryTheory.ActionCategory CategoryTheory.SingleObj Quiver
 
+#print IsFreeGroupoid.Generators /-
 /-- `is_free_groupoid.generators G` is a type synonym for `G`. We think of this as
 the vertices of the generating quiver of `G` when `G` is free. We can't use `G` directly,
 since `G` already has a quiver instance from being a groupoid. -/
@@ -69,7 +70,9 @@ since `G` already has a quiver instance from being a groupoid. -/
 def IsFreeGroupoid.Generators (G) [Groupoid G] :=
   G
 #align is_free_groupoid.generators IsFreeGroupoid.Generators
+-/
 
+#print IsFreeGroupoid /-
 /-- A groupoid `G` is free when we have the following data:
  - a quiver on `is_free_groupoid.generators G` (a type synonym for `G`)
  - a function `of` taking a generating arrow to a morphism in `G`
@@ -85,11 +88,18 @@ class IsFreeGroupoid (G) [Groupoid.{v} G] where
     ∀ {X : Type v} [Group X] (f : Labelling (IsFreeGroupoid.Generators G) X),
       ∃! F : G ⥤ CategoryTheory.SingleObj X, ∀ (a b) (g : a ⟶ b), F.map (of g) = f g
 #align is_free_groupoid IsFreeGroupoid
+-/
 
 namespace IsFreeGroupoid
 
 attribute [instance] quiver_generators
 
+/- warning: is_free_groupoid.ext_functor -> IsFreeGroupoid.ext_functor is a dubious translation:
+lean 3 declaration is
+  forall {G : Type.{u2}} [_inst_1 : CategoryTheory.Groupoid.{u1, u2} G] [_inst_2 : IsFreeGroupoid.{u1, u2} G _inst_1] {X : Type.{u1}} [_inst_3 : Group.{u1} X] (f : CategoryTheory.Functor.{u1, u1, u2, 0} G (CategoryTheory.Groupoid.toCategory.{u1, u2} G _inst_1) (CategoryTheory.SingleObj.{u1} X) (CategoryTheory.SingleObj.category.{u1} X (DivInvMonoid.toMonoid.{u1} X (Group.toDivInvMonoid.{u1} X _inst_3)))) (g : CategoryTheory.Functor.{u1, u1, u2, 0} G (CategoryTheory.Groupoid.toCategory.{u1, u2} G _inst_1) (CategoryTheory.SingleObj.{u1} X) (CategoryTheory.SingleObj.category.{u1} X (DivInvMonoid.toMonoid.{u1} X (Group.toDivInvMonoid.{u1} X _inst_3)))), (forall (a : IsFreeGroupoid.Generators.{u2, u1} G _inst_1) (b : IsFreeGroupoid.Generators.{u2, u1} G _inst_1) (e : Quiver.Hom.{succ u1, u2} (IsFreeGroupoid.Generators.{u2, u1} G _inst_1) (IsFreeGroupoid.quiverGenerators.{u1, u2} G _inst_1 _inst_2) a b), Eq.{succ u1} (Quiver.Hom.{succ u1, 0} (CategoryTheory.SingleObj.{u1} X) (CategoryTheory.CategoryStruct.toQuiver.{u1, 0} (CategoryTheory.SingleObj.{u1} X) (CategoryTheory.Category.toCategoryStruct.{u1, 0} (CategoryTheory.SingleObj.{u1} X) (CategoryTheory.SingleObj.category.{u1} X (DivInvMonoid.toMonoid.{u1} X (Group.toDivInvMonoid.{u1} X _inst_3))))) (CategoryTheory.Functor.obj.{u1, u1, u2, 0} G (CategoryTheory.Groupoid.toCategory.{u1, u2} G _inst_1) (CategoryTheory.SingleObj.{u1} X) (CategoryTheory.SingleObj.category.{u1} X (DivInvMonoid.toMonoid.{u1} X (Group.toDivInvMonoid.{u1} X _inst_3))) f ((fun (this : G) => this) a)) (CategoryTheory.Functor.obj.{u1, u1, u2, 0} G (CategoryTheory.Groupoid.toCategory.{u1, u2} G _inst_1) (CategoryTheory.SingleObj.{u1} X) (CategoryTheory.SingleObj.category.{u1} X (DivInvMonoid.toMonoid.{u1} X (Group.toDivInvMonoid.{u1} X _inst_3))) f b)) (CategoryTheory.Functor.map.{u1, u1, u2, 0} G (CategoryTheory.Groupoid.toCategory.{u1, u2} G _inst_1) (CategoryTheory.SingleObj.{u1} X) (CategoryTheory.SingleObj.category.{u1} X (DivInvMonoid.toMonoid.{u1} X (Group.toDivInvMonoid.{u1} X _inst_3))) f ((fun (this : G) => this) a) b (IsFreeGroupoid.of.{u1, u2} G _inst_1 _inst_2 a b e)) (CategoryTheory.Functor.map.{u1, u1, u2, 0} G (CategoryTheory.Groupoid.toCategory.{u1, u2} G _inst_1) (CategoryTheory.SingleObj.{u1} X) (CategoryTheory.SingleObj.category.{u1} X (DivInvMonoid.toMonoid.{u1} X (Group.toDivInvMonoid.{u1} X _inst_3))) g ((fun (this : G) => this) a) b (IsFreeGroupoid.of.{u1, u2} G _inst_1 _inst_2 a b e))) -> (Eq.{succ (max u1 u2)} (CategoryTheory.Functor.{u1, u1, u2, 0} G (CategoryTheory.Groupoid.toCategory.{u1, u2} G _inst_1) (CategoryTheory.SingleObj.{u1} X) (CategoryTheory.SingleObj.category.{u1} X (DivInvMonoid.toMonoid.{u1} X (Group.toDivInvMonoid.{u1} X _inst_3)))) f g)
+but is expected to have type
+  forall {G : Type.{u1}} [_inst_1 : CategoryTheory.Groupoid.{u2, u1} G] [_inst_2 : IsFreeGroupoid.{u2, u1} G _inst_1] {X : Type.{u2}} [_inst_3 : Group.{u2} X] (f : CategoryTheory.Functor.{u2, u2, u1, 0} G (CategoryTheory.Groupoid.toCategory.{u2, u1} G _inst_1) (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.SingleObj.category.{u2} X (DivInvMonoid.toMonoid.{u2} X (Group.toDivInvMonoid.{u2} X _inst_3)))) (g : CategoryTheory.Functor.{u2, u2, u1, 0} G (CategoryTheory.Groupoid.toCategory.{u2, u1} G _inst_1) (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.SingleObj.category.{u2} X (DivInvMonoid.toMonoid.{u2} X (Group.toDivInvMonoid.{u2} X _inst_3)))), (forall (a : IsFreeGroupoid.Generators.{u1, u2} G _inst_1) (b : IsFreeGroupoid.Generators.{u1, u2} G _inst_1) (e : Quiver.Hom.{succ u2, u1} (IsFreeGroupoid.Generators.{u1, u2} G _inst_1) (IsFreeGroupoid.quiverGenerators.{u2, u1} G _inst_1 _inst_2) a b), Eq.{succ u2} (Quiver.Hom.{succ u2, 0} (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.CategoryStruct.toQuiver.{u2, 0} (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.Category.toCategoryStruct.{u2, 0} (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.SingleObj.category.{u2} X (DivInvMonoid.toMonoid.{u2} X (Group.toDivInvMonoid.{u2} X _inst_3))))) (Prefunctor.obj.{succ u2, succ u2, u1, 0} G (CategoryTheory.CategoryStruct.toQuiver.{u2, u1} G (CategoryTheory.Category.toCategoryStruct.{u2, u1} G (CategoryTheory.Groupoid.toCategory.{u2, u1} G _inst_1))) (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.CategoryStruct.toQuiver.{u2, 0} (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.Category.toCategoryStruct.{u2, 0} (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.SingleObj.category.{u2} X (DivInvMonoid.toMonoid.{u2} X (Group.toDivInvMonoid.{u2} X _inst_3))))) (CategoryTheory.Functor.toPrefunctor.{u2, u2, u1, 0} G (CategoryTheory.Groupoid.toCategory.{u2, u1} G _inst_1) (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.SingleObj.category.{u2} X (DivInvMonoid.toMonoid.{u2} X (Group.toDivInvMonoid.{u2} X _inst_3))) f) ([mdata let_fun:1 (fun (this : G) => this) a])) (Prefunctor.obj.{succ u2, succ u2, u1, 0} G (CategoryTheory.CategoryStruct.toQuiver.{u2, u1} G (CategoryTheory.Category.toCategoryStruct.{u2, u1} G (CategoryTheory.Groupoid.toCategory.{u2, u1} G _inst_1))) (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.CategoryStruct.toQuiver.{u2, 0} (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.Category.toCategoryStruct.{u2, 0} (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.SingleObj.category.{u2} X (DivInvMonoid.toMonoid.{u2} X (Group.toDivInvMonoid.{u2} X _inst_3))))) (CategoryTheory.Functor.toPrefunctor.{u2, u2, u1, 0} G (CategoryTheory.Groupoid.toCategory.{u2, u1} G _inst_1) (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.SingleObj.category.{u2} X (DivInvMonoid.toMonoid.{u2} X (Group.toDivInvMonoid.{u2} X _inst_3))) f) b)) (Prefunctor.map.{succ u2, succ u2, u1, 0} G (CategoryTheory.CategoryStruct.toQuiver.{u2, u1} G (CategoryTheory.Category.toCategoryStruct.{u2, u1} G (CategoryTheory.Groupoid.toCategory.{u2, u1} G _inst_1))) (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.CategoryStruct.toQuiver.{u2, 0} (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.Category.toCategoryStruct.{u2, 0} (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.SingleObj.category.{u2} X (DivInvMonoid.toMonoid.{u2} X (Group.toDivInvMonoid.{u2} X _inst_3))))) (CategoryTheory.Functor.toPrefunctor.{u2, u2, u1, 0} G (CategoryTheory.Groupoid.toCategory.{u2, u1} G _inst_1) (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.SingleObj.category.{u2} X (DivInvMonoid.toMonoid.{u2} X (Group.toDivInvMonoid.{u2} X _inst_3))) f) ([mdata let_fun:1 (fun (this : G) => this) a]) b (IsFreeGroupoid.of.{u2, u1} G _inst_1 _inst_2 a b e)) (Prefunctor.map.{succ u2, succ u2, u1, 0} G (CategoryTheory.CategoryStruct.toQuiver.{u2, u1} G (CategoryTheory.Category.toCategoryStruct.{u2, u1} G (CategoryTheory.Groupoid.toCategory.{u2, u1} G _inst_1))) (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.CategoryStruct.toQuiver.{u2, 0} (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.Category.toCategoryStruct.{u2, 0} (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.SingleObj.category.{u2} X (DivInvMonoid.toMonoid.{u2} X (Group.toDivInvMonoid.{u2} X _inst_3))))) (CategoryTheory.Functor.toPrefunctor.{u2, u2, u1, 0} G (CategoryTheory.Groupoid.toCategory.{u2, u1} G _inst_1) (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.SingleObj.category.{u2} X (DivInvMonoid.toMonoid.{u2} X (Group.toDivInvMonoid.{u2} X _inst_3))) g) ([mdata let_fun:1 (fun (this : G) => this) a]) b (IsFreeGroupoid.of.{u2, u1} G _inst_1 _inst_2 a b e))) -> (Eq.{max (succ u2) (succ u1)} (CategoryTheory.Functor.{u2, u2, u1, 0} G (CategoryTheory.Groupoid.toCategory.{u2, u1} G _inst_1) (CategoryTheory.SingleObj.{u2} X) (CategoryTheory.SingleObj.category.{u2} X (DivInvMonoid.toMonoid.{u2} X (Group.toDivInvMonoid.{u2} X _inst_3)))) f g)
+Case conversion may be inaccurate. Consider using '#align is_free_groupoid.ext_functor IsFreeGroupoid.ext_functorₓ'. -/
 /-- Two functors from a free groupoid to a group are equal when they agree on the generating
 quiver. -/
 @[ext]
@@ -100,6 +110,7 @@ theorem ext_functor {G} [Groupoid.{v} G] [IsFreeGroupoid G] {X : Type v} [Group
   trans (u _ h) (u _ fun _ _ _ => rfl).symm
 #align is_free_groupoid.ext_functor IsFreeGroupoid.ext_functor
 
+#print IsFreeGroupoid.actionGroupoidIsFree /-
 /-- An action groupoid over a free group is free. More generally, one could show that the groupoid
 of elements over a free groupoid is free, but this version is easier to prove and suffices for our
 purposes.
@@ -143,6 +154,7 @@ instance actionGroupoidIsFree {G A : Type u} [Group G] [IsFreeGroup G] [MulActio
         intros
         simp only [← this, uncurry_map, curry_apply_left, coe_back, hom_of_pair.val]
 #align is_free_groupoid.action_groupoid_is_free IsFreeGroupoid.actionGroupoidIsFree
+-/
 
 namespace SpanningTree
 
@@ -158,6 +170,7 @@ private def root' : G :=
   show T from root T
 #align is_free_groupoid.spanning_tree.root' is_free_groupoid.spanning_tree.root'
 
+#print IsFreeGroupoid.SpanningTree.homOfPath /-
 -- this has to be marked noncomputable, see issue #451.
 -- It might be nicer to define this in terms of `compose_path`
 /-- A path in the tree gives a hom, by composition. -/
@@ -165,30 +178,40 @@ noncomputable def homOfPath : ∀ {a : G}, Path (root T) a → (root' T ⟶ a)
   | _, path.nil => 𝟙 _
   | a, path.cons p f => hom_of_path p ≫ Sum.recOn f.val (fun e => of e) fun e => inv (of e)
 #align is_free_groupoid.spanning_tree.hom_of_path IsFreeGroupoid.SpanningTree.homOfPath
+-/
 
+#print IsFreeGroupoid.SpanningTree.treeHom /-
 /-- For every vertex `a`, there is a canonical hom from the root, given by the path in the tree. -/
 def treeHom (a : G) : root' T ⟶ a :=
   homOfPath T default
 #align is_free_groupoid.spanning_tree.tree_hom IsFreeGroupoid.SpanningTree.treeHom
+-/
 
+#print IsFreeGroupoid.SpanningTree.treeHom_eq /-
 /-- Any path to `a` gives `tree_hom T a`, since paths in the tree are unique. -/
 theorem treeHom_eq {a : G} (p : Path (root T) a) : treeHom T a = homOfPath T p := by
   rw [tree_hom, Unique.default_eq]
 #align is_free_groupoid.spanning_tree.tree_hom_eq IsFreeGroupoid.SpanningTree.treeHom_eq
+-/
 
+#print IsFreeGroupoid.SpanningTree.treeHom_root /-
 @[simp]
 theorem treeHom_root : treeHom T (root' T) = 𝟙 _ :=
   -- this should just be `tree_hom_eq T path.nil`, but Lean treats `hom_of_path` with suspicion.
     trans
     (treeHom_eq T Path.nil) rfl
 #align is_free_groupoid.spanning_tree.tree_hom_root IsFreeGroupoid.SpanningTree.treeHom_root
+-/
 
+#print IsFreeGroupoid.SpanningTree.loopOfHom /-
 /-- Any hom in `G` can be made into a loop, by conjugating with `tree_hom`s. -/
 def loopOfHom {a b : G} (p : a ⟶ b) : End (root' T) :=
   treeHom T a ≫ p ≫ inv (treeHom T b)
 #align is_free_groupoid.spanning_tree.loop_of_hom IsFreeGroupoid.SpanningTree.loopOfHom
+-/
 
 /- ./././Mathport/Syntax/Translate/Basic.lean:635:2: warning: expanding binder collection (e «expr ∈ » wide_subquiver_symmetrify[quiver.wide_subquiver_symmetrify] T a b) -/
+#print IsFreeGroupoid.SpanningTree.loopOfHom_eq_id /-
 /-- Turning an edge in the spanning tree into a loop gives the indentity loop. -/
 theorem loopOfHom_eq_id {a b : Generators G} (e) (_ : e ∈ wideSubquiverSymmetrify T a b) :
     loopOfHom T (of e) = 𝟙 (root' T) :=
@@ -200,7 +223,9 @@ theorem loopOfHom_eq_id {a b : Generators G} (e) (_ : e ∈ wideSubquiverSymmetr
   · rw [tree_hom_eq T (path.cons default ⟨Sum.inr e, H⟩), hom_of_path]
     simp only [is_iso.inv_hom_id, category.comp_id, category.assoc, tree_hom]
 #align is_free_groupoid.spanning_tree.loop_of_hom_eq_id IsFreeGroupoid.SpanningTree.loopOfHom_eq_id
+-/
 
+#print IsFreeGroupoid.SpanningTree.functorOfMonoidHom /-
 /-- Since a hom gives a loop, any homomorphism from the vertex group at the root
     extends to a functor on the whole groupoid. -/
 @[simps]
@@ -216,7 +241,9 @@ def functorOfMonoidHom {X} [Monoid X] (f : End (root' T) →* X) : G ⥤ Categor
     rw [comp_as_mul, ← f.map_mul]
     simp only [is_iso.inv_hom_id_assoc, loop_of_hom, End.mul_def, category.assoc]
 #align is_free_groupoid.spanning_tree.functor_of_monoid_hom IsFreeGroupoid.SpanningTree.functorOfMonoidHom
+-/
 
+#print IsFreeGroupoid.SpanningTree.endIsFree /-
 /-- Given a free groupoid and an arborescence of its generating quiver, the vertex
     group at the root is freely generated by loops coming from generating arrows
     in the complement of the tree. -/
@@ -260,6 +287,7 @@ def endIsFree : IsFreeGroup (End (root' T)) :=
         · rw [loop_of_hom_eq_id T e h, ← End.one_def, E.map_one]
         · exact hE ⟨⟨a, b, e⟩, h⟩)
 #align is_free_groupoid.spanning_tree.End_is_free IsFreeGroupoid.SpanningTree.endIsFree
+-/
 
 end SpanningTree
 
@@ -269,6 +297,7 @@ private def symgen {G : Type u} [Groupoid.{v} G] [IsFreeGroupoid G] :
   id
 #align is_free_groupoid.symgen is_free_groupoid.symgen
 
+#print IsFreeGroupoid.path_nonempty_of_hom /-
 /-- If there exists a morphism `a → b` in a free groupoid, then there also exists a zigzag
 from `a` to `b` in the generating quiver. -/
 theorem path_nonempty_of_hom {G} [Groupoid.{u, u} G] [IsFreeGroupoid G] {a b : G} :
@@ -287,22 +316,33 @@ theorem path_nonempty_of_hom {G} [Groupoid.{u, u} G] [IsFreeGroupoid G] {a b : G
   apply (weakly_connected_component.eq _ _).mpr
   exact ⟨hom.to_path (Sum.inr e)⟩
 #align is_free_groupoid.path_nonempty_of_hom IsFreeGroupoid.path_nonempty_of_hom
+-/
 
+#print IsFreeGroupoid.generators_connected /-
 /-- Given a connected free groupoid, its generating quiver is rooted-connected. -/
 instance generators_connected (G) [Groupoid.{u, u} G] [IsConnected G] [IsFreeGroupoid G] (r : G) :
     RootedConnected (symgen r) :=
   ⟨fun b => path_nonempty_of_hom (CategoryTheory.nonempty_hom_of_connected_groupoid r b)⟩
 #align is_free_groupoid.generators_connected IsFreeGroupoid.generators_connected
+-/
 
+#print IsFreeGroupoid.endIsFreeOfConnectedFree /-
 /-- A vertex group in a free connected groupoid is free. With some work one could drop the
 connectedness assumption, by looking at connected components. -/
 instance endIsFreeOfConnectedFree {G} [Groupoid G] [IsConnected G] [IsFreeGroupoid G] (r : G) :
     IsFreeGroup (End r) :=
   SpanningTree.endIsFree <| geodesicSubtree (symgen r)
 #align is_free_groupoid.End_is_free_of_connected_free IsFreeGroupoid.endIsFreeOfConnectedFree
+-/
 
 end IsFreeGroupoid
 
+/- warning: subgroup_is_free_of_is_free -> subgroupIsFreeOfIsFree is a dubious translation:
+lean 3 declaration is
+  forall {G : Type.{u1}} [_inst_1 : Group.{u1} G] [_inst_2 : IsFreeGroup.{u1} G _inst_1] (H : Subgroup.{u1} G _inst_1), IsFreeGroup.{u1} (coeSort.{succ u1, succ (succ u1)} (Subgroup.{u1} G _inst_1) Type.{u1} (SetLike.hasCoeToSort.{u1, u1} (Subgroup.{u1} G _inst_1) G (Subgroup.setLike.{u1} G _inst_1)) H) (Subgroup.toGroup.{u1} G _inst_1 H)
+but is expected to have type
+  forall {G : Type.{u1}} [_inst_1 : Group.{u1} G] [_inst_2 : IsFreeGroup.{u1} G _inst_1] (H : Subgroup.{u1} G _inst_1), IsFreeGroup.{u1} (Subtype.{succ u1} G (fun (x : G) => Membership.mem.{u1, u1} G (Subgroup.{u1} G _inst_1) (SetLike.instMembership.{u1, u1} (Subgroup.{u1} G _inst_1) G (Subgroup.instSetLikeSubgroup.{u1} G _inst_1)) x H)) (Subgroup.toGroup.{u1} G _inst_1 H)
+Case conversion may be inaccurate. Consider using '#align subgroup_is_free_of_is_free subgroupIsFreeOfIsFreeₓ'. -/
 /-- The Nielsen-Schreier theorem: a subgroup of a free group is free. -/
 instance subgroupIsFreeOfIsFree {G : Type u} [Group G] [IsFreeGroup G] (H : Subgroup G) :
     IsFreeGroup H :=

mathlib commit https://github.com/leanprover-community/mathlib/commit/09079525fd01b3dda35e96adaa08d2f943e1648c

@@ -59,7 +59,7 @@ open Classical
 
 universe v u
 
-/- ./././Mathport/Syntax/Translate/Command.lean:224:11: unsupported: unusual advanced open style -/
+/- ./././Mathport/Syntax/Translate/Command.lean:229:11: unsupported: unusual advanced open style -/
 open CategoryTheory CategoryTheory.ActionCategory CategoryTheory.SingleObj Quiver
 
 /-- `is_free_groupoid.generators G` is a type synonym for `G`. We think of this as

mathlib commit https://github.com/leanprover-community/mathlib/commit/57e09a1296bfb4330ddf6624f1028ba186117d82

@@ -235,7 +235,7 @@ def endIsFree : IsFreeGroup (End (root' T)) :=
           rw [functor.map_End_apply, this, hF']
           exact dif_neg h
         intros
-        suffices ∀ {a} (p : path (root' T) a), F'.map (hom_of_path T p) = 1 by
+        suffices ∀ {a} (p : Path (root' T) a), F'.map (hom_of_path T p) = 1 by
           simp only [this, tree_hom, comp_as_mul, inv_as_inv, loop_of_hom, inv_one, mul_one,
             one_mul, functor.map_inv, functor.map_comp]
         intro a p

mathlib commit https://github.com/leanprover-community/mathlib/commit/4c586d291f189eecb9d00581aeb3dd998ac34442

@@ -188,7 +188,7 @@ def loopOfHom {a b : G} (p : a ⟶ b) : End (root' T) :=
   treeHom T a ≫ p ≫ inv (treeHom T b)
 #align is_free_groupoid.spanning_tree.loop_of_hom IsFreeGroupoid.SpanningTree.loopOfHom
 
-/- ./././Mathport/Syntax/Translate/Basic.lean:628:2: warning: expanding binder collection (e «expr ∈ » wide_subquiver_symmetrify[quiver.wide_subquiver_symmetrify] T a b) -/
+/- ./././Mathport/Syntax/Translate/Basic.lean:635:2: warning: expanding binder collection (e «expr ∈ » wide_subquiver_symmetrify[quiver.wide_subquiver_symmetrify] T a b) -/
 /-- Turning an edge in the spanning tree into a loop gives the indentity loop. -/
 theorem loopOfHom_eq_id {a b : Generators G} (e) (_ : e ∈ wideSubquiverSymmetrify T a b) :
     loopOfHom T (of e) = 𝟙 (root' T) :=

mathlib commit https://github.com/leanprover-community/mathlib/commit/3ade05ac9447ae31a22d2ea5423435e054131240

@@ -4,7 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: David Wärn
 
 ! This file was ported from Lean 3 source module group_theory.nielsen_schreier
-! leanprover-community/mathlib commit 56adee5b5eef9e734d82272918300fca4f3e7cef
+! leanprover-community/mathlib commit 1bda4fc53de6ade5ab9da36f2192e24e2084a2ce
 ! Please do not edit these lines, except to modify the commit id
 ! if you have ported upstream changes.
 -/
@@ -100,7 +100,7 @@ theorem ext_functor {G} [Groupoid.{v} G] [IsFreeGroupoid G] {X : Type v} [Group
   trans (u _ h) (u _ fun _ _ _ => rfl).symm
 #align is_free_groupoid.ext_functor IsFreeGroupoid.ext_functor
 
-/-- An action groupoid over a free froup is free. More generally, one could show that the groupoid
+/-- An action groupoid over a free group is free. More generally, one could show that the groupoid
 of elements over a free groupoid is free, but this version is easier to prove and suffices for our
 purposes.
 

mathlib commit https://github.com/leanprover-community/mathlib/commit/bd9851ca476957ea4549eb19b40e7b5ade9428cc

Reference the newly created issues #12094 and #12096, as well as the pre-existing #5171. Change all references to #10927 to #5171. Some of these changes were not labelled as "porting note"; change this for good measure.

@@ -63,7 +63,7 @@ open CategoryTheory CategoryTheory.ActionCategory CategoryTheory.SingleObj Quive
 /-- `IsFreeGroupoid.Generators G` is a type synonym for `G`. We think of this as
 the vertices of the generating quiver of `G` when `G` is free. We can't use `G` directly,
 since `G` already has a quiver instance from being a groupoid. -/
--- Porting note: @[nolint has_nonempty_instance]
+-- Porting note(#5171): @[nolint has_nonempty_instance]
 @[nolint unusedArguments]
 def IsFreeGroupoid.Generators (G) [Groupoid G] :=
   G

We remove all but one open Classicals, instead preferring to use open scoped Classical. The only real side-effect this led to is moving a couple declarations to use Exists.choose instead of Classical.choose.

The first few commits are explicitly labelled regex replaces for ease of review.

@@ -52,7 +52,7 @@ free group, free groupoid, Nielsen-Schreier
 
 noncomputable section
 
-open Classical
+open scoped Classical
 
 universe v u
 

@@ -291,7 +291,7 @@ theorem path_nonempty_of_hom {G} [Groupoid.{u, u} G] [IsFreeGroupoid G] {a b : G
 /-- Given a connected free groupoid, its generating quiver is rooted-connected. -/
 instance generators_connected (G) [Groupoid.{u, u} G] [IsConnected G] [IsFreeGroupoid G] (r : G) :
     RootedConnected (symgen r) :=
-  ⟨fun b => path_nonempty_of_hom (CategoryTheory.nonempty_hom_of_connected_groupoid r b)⟩
+  ⟨fun b => path_nonempty_of_hom (CategoryTheory.nonempty_hom_of_preconnected_groupoid r b)⟩
 #align is_free_groupoid.generators_connected IsFreeGroupoid.generators_connected
 
 /-- A vertex group in a free connected groupoid is free. With some work one could drop the

This prepares for the introduction of a non-dependent synonym of FunLike, which helps a lot with keeping #8386 readable.

This is entirely search-and-replace in 680197f combined with manual fixes in 4145626, e900597 and b8428f8. The commands that generated this change:

sed -i 's/\bFunLike\b/DFunLike/g' {Archive,Counterexamples,Mathlib,test}/**/*.lean
sed -i 's/\btoFunLike\b/toDFunLike/g' {Archive,Counterexamples,Mathlib,test}/**/*.lean
sed -i 's/import Mathlib.Data.DFunLike/import Mathlib.Data.FunLike/g' {Archive,Counterexamples,Mathlib,test}/**/*.lean
sed -i 's/\bHom_FunLike\b/Hom_DFunLike/g' {Archive,Counterexamples,Mathlib,test}/**/*.lean     
sed -i 's/\binstFunLike\b/instDFunLike/g' {Archive,Counterexamples,Mathlib,test}/**/*.lean
sed -i 's/\bfunLike\b/instDFunLike/g' {Archive,Counterexamples,Mathlib,test}/**/*.lean
sed -i 's/\btoo many metavariables to apply `fun_like.has_coe_to_fun`/too many metavariables to apply `DFunLike.hasCoeToFun`/g' {Archive,Counterexamples,Mathlib,test}/**/*.lean

Co-authored-by: Anne Baanen <Vierkantor@users.noreply.github.com>

@@ -120,7 +120,7 @@ instance actionGroupoidIsFree {G A : Type u} [Group G] [IsFreeGroup G] [MulActio
     refine' ⟨uncurry F' _, _, _⟩
     · suffices SemidirectProduct.rightHom.comp F' = MonoidHom.id _ by
         -- Porting note: `MonoidHom.ext_iff` has been deprecated.
-        exact FunLike.ext_iff.mp this
+        exact DFunLike.ext_iff.mp this
       apply IsFreeGroup.ext_hom (fun x ↦ ?_)
       rw [MonoidHom.comp_apply, hF']
       rfl

Currently, the class IsFreeGroup contains data (namely, a specific set of generators). This is bad, as there are many sets of generators in a free group, and changing sets of generators happens all the time in geometric group theory. We switch to a design in which

• we define FreeGroupBasis, following the definition and API of bases of vector spaces. Most existing API around IsFreeGroup is transferred to lemmas taking a free group basis as a variable.
• The typeclass IsFreeGroup is Prop-valued, and requires only the existence of a free group basis.

@@ -121,7 +121,7 @@ instance actionGroupoidIsFree {G A : Type u} [Group G] [IsFreeGroup G] [MulActio
     · suffices SemidirectProduct.rightHom.comp F' = MonoidHom.id _ by
         -- Porting note: `MonoidHom.ext_iff` has been deprecated.
         exact FunLike.ext_iff.mp this
-      ext
+      apply IsFreeGroup.ext_hom (fun x ↦ ?_)
       rw [MonoidHom.comp_apply, hF']
       rfl
     · rintro ⟨⟨⟩, a : A⟩ ⟨⟨⟩, b⟩ ⟨e, h : IsFreeGroup.of e • a = b⟩
@@ -222,7 +222,7 @@ def functorOfMonoidHom {X} [Monoid X] (f : End (root' T) →* X) : G ⥤ Categor
 /-- Given a free groupoid and an arborescence of its generating quiver, the vertex
     group at the root is freely generated by loops coming from generating arrows
     in the complement of the tree. -/
-def endIsFree : IsFreeGroup (End (root' T)) :=
+lemma endIsFree : IsFreeGroup (End (root' T)) :=
   IsFreeGroup.ofUniqueLift ((wideSubquiverEquivSetTotal <| wideSubquiverSymmetrify T)ᶜ : Set _)
     (fun e => loopOfHom T (of e.val.hom))
     (by

@@ -6,7 +6,7 @@ Authors: David Wärn
 import Mathlib.CategoryTheory.Action
 import Mathlib.Combinatorics.Quiver.Arborescence
 import Mathlib.Combinatorics.Quiver.ConnectedComponent
-import Mathlib.GroupTheory.IsFreeGroup
+import Mathlib.GroupTheory.FreeGroup.IsFreeGroup
 
 #align_import group_theory.nielsen_schreier from "leanprover-community/mathlib"@"1bda4fc53de6ade5ab9da36f2192e24e2084a2ce"
 

• depends on: #5966

Co-authored-by: Eric Wieser <wieser.eric@gmail.com> Co-authored-by: Scott Morrison <scott.morrison@gmail.com>

@@ -2,17 +2,14 @@
 Copyright (c) 2021 David Wärn. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: David Wärn
-
-! This file was ported from Lean 3 source module group_theory.nielsen_schreier
-! leanprover-community/mathlib commit 1bda4fc53de6ade5ab9da36f2192e24e2084a2ce
-! Please do not edit these lines, except to modify the commit id
-! if you have ported upstream changes.
 -/
 import Mathlib.CategoryTheory.Action
 import Mathlib.Combinatorics.Quiver.Arborescence
 import Mathlib.Combinatorics.Quiver.ConnectedComponent
 import Mathlib.GroupTheory.IsFreeGroup
 
+#align_import group_theory.nielsen_schreier from "leanprover-community/mathlib"@"1bda4fc53de6ade5ab9da36f2192e24e2084a2ce"
+
 /-!
 # The Nielsen-Schreier theorem
 

This is the second half of the changes originally in #5699, removing all occurrences of ; after a space and implementing a linter rule to enforce it.

In most cases this 2-character substring has a space after it, so the following command was run first:

find . -type f -name "*.lean" -exec sed -i -E 's/ ; /; /g' {} \;

The remaining cases were few enough in number that they were done manually.

@@ -284,7 +284,7 @@ theorem path_nonempty_of_hom {G} [Groupoid.{u, u} G] [IsFreeGroupoid G] {a b : G
   let f : G → X := fun g => FreeGroup.of (WeaklyConnectedComponent.mk g)
   let F : G ⥤ CategoryTheory.SingleObj.{u} (X : Type u) := SingleObj.differenceFunctor f
   change (F.map p) = ((@CategoryTheory.Functor.const G _ _ (SingleObj.category X)).obj ()).map p
-  congr ; ext
+  congr; ext
   rw [Functor.const_obj_map, id_as_one, differenceFunctor_map, @mul_inv_eq_one _ _ (f _)]
   apply congr_arg FreeGroup.of
   apply (WeaklyConnectedComponent.eq _ _).mpr

Run codespell Mathlib and keep some suggestions.

@@ -194,7 +194,7 @@ def loopOfHom {a b : G} (p : a ⟶ b) : End (root' T) :=
   treeHom T a ≫ p ≫ inv (treeHom T b)
 #align is_free_groupoid.spanning_tree.loop_of_hom IsFreeGroupoid.SpanningTree.loopOfHom
 
-/-- Turning an edge in the spanning tree into a loop gives the indentity loop. -/
+/-- Turning an edge in the spanning tree into a loop gives the identity loop. -/
 theorem loopOfHom_eq_id {a b : Generators G} (e) (H : e ∈ wideSubquiverSymmetrify T a b) :
     loopOfHom T (of e) = 𝟙 (root' T) := by
   rw [loopOfHom, ← Category.assoc, IsIso.comp_inv_eq, Category.id_comp]