diff --git a/src/stages/adt_generator/README b/src/stages/adt_generator/README
new file mode 100644
index 000000000..20ecdfd43
--- /dev/null
+++ b/src/stages/adt_generator/README
@@ -0,0 +1,7 @@
+Build with:
+
+    dune build adt_generator.a
+
+Run with
+
+    python ./generator.py
diff --git a/src/stages/adt_generator/a.ml b/src/stages/adt_generator/a.ml
new file mode 100644
index 000000000..f1d8b2fb1
--- /dev/null
+++ b/src/stages/adt_generator/a.ml
@@ -0,0 +1,17 @@
+type root =
+| A of a
+| B of int
+| C of string
+
+and a = {
+  a1 : ta1 ;
+  a2 : ta2 ;
+}
+
+and ta1 =
+| X of root
+| Y of ta2
+
+and ta2 =
+| Z of ta2
+| W of unit
diff --git a/src/stages/adt_generator/adt_generator.ml b/src/stages/adt_generator/adt_generator.ml
new file mode 100644
index 000000000..9c1ff4b88
--- /dev/null
+++ b/src/stages/adt_generator/adt_generator.ml
@@ -0,0 +1,2 @@
+module A = A
+module Use_a_fold = Use_a_fold
diff --git a/src/stages/adt_generator/dune b/src/stages/adt_generator/dune
new file mode 100644
index 000000000..4a52c6088
--- /dev/null
+++ b/src/stages/adt_generator/dune
@@ -0,0 +1,18 @@
+(rule
+  (target fold.ml)
+  (deps generator.py)
+  (action (with-stdout-to fold.ml (run python3 ./generator.py)))
+  (mode (promote (until-clean))))
+; (library
+;   (name adt_generator)
+;   (public_name ligo.adt_generator)
+;   (libraries
+;   )
+; )
+
+(executable
+  (name adt_generator)
+  (public_name ligo.adt_generator)
+  (libraries
+  )
+)
diff --git a/src/stages/adt_generator/fold.ml b/src/stages/adt_generator/fold.ml
new file mode 100644
index 000000000..4e4c41357
--- /dev/null
+++ b/src/stages/adt_generator/fold.ml
@@ -0,0 +1,184 @@
+open A
+
+type root' =
+  | A' of a'
+  | B' of int
+  | C' of string
+and a' =
+  {
+    a1' : ta1' ;
+    a2' : ta2' ;
+  }
+and ta1' =
+  | X' of root'
+  | Y' of ta2'
+and ta2' =
+  | Z' of ta2'
+  | W' of unit
+
+type 'state continue_fold =
+  {
+    root : root -> 'state -> (root' * 'state) ;
+    root_A : a -> 'state -> (a' * 'state) ;
+    root_B : int -> 'state -> (int * 'state) ;
+    root_C : string -> 'state -> (string * 'state) ;
+    a : a -> 'state -> (a' * 'state) ;
+    a_a1 : ta1 -> 'state -> (ta1' * 'state) ;
+    a_a2 : ta2 -> 'state -> (ta2' * 'state) ;
+    ta1 : ta1 -> 'state -> (ta1' * 'state) ;
+    ta1_X : root -> 'state -> (root' * 'state) ;
+    ta1_Y : ta2 -> 'state -> (ta2' * 'state) ;
+    ta2 : ta2 -> 'state -> (ta2' * 'state) ;
+    ta2_Z : ta2 -> 'state -> (ta2' * 'state) ;
+    ta2_W : unit -> 'state -> (unit * 'state) ;
+  }
+
+type 'state fold_config =
+  {
+    root : root -> 'state -> ('state continue_fold) -> (root' * 'state) ;
+    root_pre_state : root -> 'state -> 'state ;
+    root_post_state : root -> root' -> 'state -> 'state ;
+    root_A : a -> 'state -> ('state continue_fold) -> (a' * 'state) ;
+    root_B : int -> 'state -> ('state continue_fold) -> (int * 'state) ;
+    root_C : string -> 'state -> ('state continue_fold) -> (string * 'state) ;
+    a : a -> 'state -> ('state continue_fold) -> (a' * 'state) ;
+    a_pre_state : a -> 'state -> 'state ;
+    a_post_state : a -> a' -> 'state -> 'state ;
+    a_a1 : ta1 -> 'state -> ('state continue_fold) -> (ta1' * 'state) ;
+    a_a2 : ta2 -> 'state -> ('state continue_fold) -> (ta2' * 'state) ;
+    ta1 : ta1 -> 'state -> ('state continue_fold) -> (ta1' * 'state) ;
+    ta1_pre_state : ta1 -> 'state -> 'state ;
+    ta1_post_state : ta1 -> ta1' -> 'state -> 'state ;
+    ta1_X : root -> 'state -> ('state continue_fold) -> (root' * 'state) ;
+    ta1_Y : ta2 -> 'state -> ('state continue_fold) -> (ta2' * 'state) ;
+    ta2 : ta2 -> 'state -> ('state continue_fold) -> (ta2' * 'state) ;
+    ta2_pre_state : ta2 -> 'state -> 'state ;
+    ta2_post_state : ta2 -> ta2' -> 'state -> 'state ;
+    ta2_Z : ta2 -> 'state -> ('state continue_fold) -> (ta2' * 'state) ;
+    ta2_W : unit -> 'state -> ('state continue_fold) -> (unit * 'state) ;
+  }
+
+(* Curries the "visitor" argument to the folds (non-customizable traversal functions). *)
+let rec mk_continue_fold : type state . state fold_config -> state continue_fold = fun visitor ->
+  {
+    root = fold_root visitor ;
+    root_A = fold_root_A visitor ;
+    root_B = fold_root_B visitor ;
+    root_C = fold_root_C visitor ;
+    a = fold_a visitor ;
+    a_a1 = fold_a_a1 visitor ;
+    a_a2 = fold_a_a2 visitor ;
+    ta1 = fold_ta1 visitor ;
+    ta1_X = fold_ta1_X visitor ;
+    ta1_Y = fold_ta1_Y visitor ;
+    ta2 = fold_ta2 visitor ;
+    ta2_Z = fold_ta2_Z visitor ;
+    ta2_W = fold_ta2_W visitor ;
+}
+
+and fold_root : type state . state fold_config -> root -> state -> (root' * state) = fun visitor x state ->
+  let continue_fold : state continue_fold = mk_continue_fold visitor in
+  let state = visitor.root_pre_state x state in
+  let (new_x, state) = visitor.root x state continue_fold in
+  let state = visitor.root_post_state x new_x state in
+  (new_x, state)
+
+and fold_root_A : type state . state fold_config -> a -> state -> (a' * state) = fun visitor x state ->
+  let continue_fold : state continue_fold = mk_continue_fold visitor in
+  visitor.root_A x state continue_fold
+
+and fold_root_B : type state . state fold_config -> int -> state -> (int * state) = fun visitor x state ->
+  let continue_fold : state continue_fold = mk_continue_fold visitor in
+  visitor.root_B x state continue_fold
+
+and fold_root_C : type state . state fold_config -> string -> state -> (string * state) = fun visitor x state ->
+  let continue_fold : state continue_fold = mk_continue_fold visitor in
+  visitor.root_C x state continue_fold
+
+and fold_a : type state . state fold_config -> a -> state -> (a' * state) = fun visitor x state ->
+  let continue_fold : state continue_fold = mk_continue_fold visitor in
+  let state = visitor.a_pre_state x state in
+  let (new_x, state) = visitor.a x state continue_fold in
+  let state = visitor.a_post_state x new_x state in
+  (new_x, state)
+
+and fold_a_a1 : type state . state fold_config -> ta1 -> state -> (ta1' * state) = fun visitor x state ->
+  let continue_fold : state continue_fold = mk_continue_fold visitor in
+  visitor.a_a1 x state continue_fold
+
+and fold_a_a2 : type state . state fold_config -> ta2 -> state -> (ta2' * state) = fun visitor x state ->
+  let continue_fold : state continue_fold = mk_continue_fold visitor in
+  visitor.a_a2 x state continue_fold
+
+and fold_ta1 : type state . state fold_config -> ta1 -> state -> (ta1' * state) = fun visitor x state ->
+  let continue_fold : state continue_fold = mk_continue_fold visitor in
+  let state = visitor.ta1_pre_state x state in
+  let (new_x, state) = visitor.ta1 x state continue_fold in
+  let state = visitor.ta1_post_state x new_x state in
+  (new_x, state)
+
+and fold_ta1_X : type state . state fold_config -> root -> state -> (root' * state) = fun visitor x state ->
+  let continue_fold : state continue_fold = mk_continue_fold visitor in
+  visitor.ta1_X x state continue_fold
+
+and fold_ta1_Y : type state . state fold_config -> ta2 -> state -> (ta2' * state) = fun visitor x state ->
+  let continue_fold : state continue_fold = mk_continue_fold visitor in
+  visitor.ta1_Y x state continue_fold
+
+and fold_ta2 : type state . state fold_config -> ta2 -> state -> (ta2' * state) = fun visitor x state ->
+  let continue_fold : state continue_fold = mk_continue_fold visitor in
+  let state = visitor.ta2_pre_state x state in
+  let (new_x, state) = visitor.ta2 x state continue_fold in
+  let state = visitor.ta2_post_state x new_x state in
+  (new_x, state)
+
+and fold_ta2_Z : type state . state fold_config -> ta2 -> state -> (ta2' * state) = fun visitor x state ->
+  let continue_fold : state continue_fold = mk_continue_fold visitor in
+  visitor.ta2_Z x state continue_fold
+
+and fold_ta2_W : type state . state fold_config -> unit -> state -> (unit * state) = fun visitor x state ->
+  let continue_fold : state continue_fold = mk_continue_fold visitor in
+  visitor.ta2_W x state continue_fold
+
+let no_op : 'a fold_config = {
+  root = (fun v state continue ->
+    match v with
+    | A v -> let (v, state) = continue.root_A v state in (A' v, state)
+    | B v -> let (v, state) = continue.root_B v state in (B' v, state)
+    | C v -> let (v, state) = continue.root_C v state in (C' v, state)
+  );
+  root_pre_state = (fun v state -> ignore v; state) ;
+  root_post_state = (fun v new_v state -> ignore (v, new_v); state) ;
+  root_A = (fun v state continue -> continue.a v state ) ;
+  root_B = (fun v state continue -> ignore continue; (v, state) ) ;
+  root_C = (fun v state continue -> ignore continue; (v, state) ) ;
+  a = (fun v state continue ->
+    match v with
+      { a1; a2; } ->
+      let (a1', state) = continue.a_a1 a1 state in
+      let (a2', state) = continue.a_a2 a2 state in
+      ({ a1'; a2'; }, state)
+  );
+  a_pre_state = (fun v state -> ignore v; state) ;
+  a_post_state = (fun v new_v state -> ignore (v, new_v); state) ;
+  a_a1 = (fun v state continue -> continue.ta1 v state ) ;
+  a_a2 = (fun v state continue -> continue.ta2 v state ) ;
+  ta1 = (fun v state continue ->
+    match v with
+    | X v -> let (v, state) = continue.ta1_X v state in (X' v, state)
+    | Y v -> let (v, state) = continue.ta1_Y v state in (Y' v, state)
+  );
+  ta1_pre_state = (fun v state -> ignore v; state) ;
+  ta1_post_state = (fun v new_v state -> ignore (v, new_v); state) ;
+  ta1_X = (fun v state continue -> continue.root v state ) ;
+  ta1_Y = (fun v state continue -> continue.ta2 v state ) ;
+  ta2 = (fun v state continue ->
+    match v with
+    | Z v -> let (v, state) = continue.ta2_Z v state in (Z' v, state)
+    | W v -> let (v, state) = continue.ta2_W v state in (W' v, state)
+  );
+  ta2_pre_state = (fun v state -> ignore v; state) ;
+  ta2_post_state = (fun v new_v state -> ignore (v, new_v); state) ;
+  ta2_Z = (fun v state continue -> continue.ta2 v state ) ;
+  ta2_W = (fun v state continue -> ignore continue; (v, state) ) ;
+}
diff --git a/src/stages/adt_generator/generator.py b/src/stages/adt_generator/generator.py
new file mode 100644
index 000000000..65fe21878
--- /dev/null
+++ b/src/stages/adt_generator/generator.py
@@ -0,0 +1,134 @@
+moduleName = "A"
+adts = [
+  # typename, variant?, fields_or_ctors
+  ("root", True, [
+      # ctor, builtin, type
+      ("A", False, "a"),
+      ("B", True, "int"),
+      ("C", True, "string"),
+  ]),
+  ("a", False, [
+    ("a1", False, "ta1"),
+    ("a2", False, "ta2"),
+  ]),
+  ("ta1", True, [
+      ("X", False, "root"),
+      ("Y", False, "ta2"),
+  ]),
+  ("ta2", True, [
+      ("Z", False, "ta2"),
+      ("W", True, "unit"),
+  ]),
+]
+
+from collections import namedtuple
+adt = namedtuple('adt', ['name', 'newName', 'isVariant', 'ctorsOrFields'])
+ctorOrField = namedtuple('ctorOrField', ['name', 'newName', 'isBuiltin', 'type_', 'newType'])
+adts = [
+  adt(
+    name = name,
+    newName = f"{name}'",
+    isVariant = isVariant,
+    ctorsOrFields = [
+      ctorOrField(
+        name = cf,
+        newName = f"{cf}'",
+        isBuiltin = isBuiltin,
+        type_ = type_,
+        newType = type_ if isBuiltin else f"{type_}'",
+      )
+      for (cf, isBuiltin, type_) in ctors
+    ],
+  )
+  for (name, isVariant, ctors) in adts
+]
+
+print("open %s" % moduleName)
+
+print("")
+for (index, t) in enumerate(adts):
+  typeOrAnd = "type" if index == 0 else "and"
+  print(f"{typeOrAnd} {t.newName} =")
+  if t.isVariant:
+    for c in t.ctorsOrFields:
+      print(f"  | {c.newName} of {c.newType}")
+  else:
+    print("  {")
+    for f in t.ctorsOrFields:
+      print(f"    {f.newName} : {f.newType} ;")
+    print("  }")
+
+print("")
+print(f"type 'state continue_fold =")
+print("  {")
+for t in adts:
+  print(f"    {t.name} : {t.name} -> 'state -> ({t.newName} * 'state) ;")
+  for c in t.ctorsOrFields:
+    print(f"    {t.name}_{c.name} : {c.type_} -> 'state -> ({c.newType} * 'state) ;")
+print("  }")
+
+print("")
+print(f"type 'state fold_config =")
+print("  {")
+for t in adts:
+  print(f"    {t.name} : {t.name} -> 'state -> ('state continue_fold) -> ({t.newName} * 'state) ;")
+  print(f"    {t.name}_pre_state : {t.name} -> 'state -> 'state ;")
+  print(f"    {t.name}_post_state : {t.name} -> {t.newName} -> 'state -> 'state ;")
+  for c in t.ctorsOrFields:
+    print(f"    {t.name}_{c.name} : {c.type_} -> 'state -> ('state continue_fold) -> ({c.newType} * 'state) ;")
+print("  }")
+
+print("")
+print('(* Curries the "visitor" argument to the folds (non-customizable traversal functions). *)')
+print("let rec mk_continue_fold : type state . state fold_config -> state continue_fold = fun visitor ->")
+print("  {")
+for t in adts:
+  print(f"    {t.name} = fold_{t.name} visitor ;")
+  for c in t.ctorsOrFields:
+    print(f"    {t.name}_{c.name} = fold_{t.name}_{c.name} visitor ;")
+print("}")
+print("")
+
+for t in adts:
+  print(f"and fold_{t.name} : type state . state fold_config -> {t.name} -> state -> ({t.newName} * state) = fun visitor x state ->")
+  print("  let continue_fold : state continue_fold = mk_continue_fold visitor in")
+  print(f"  let state = visitor.{t.name}_pre_state x state in")
+  print(f"  let (new_x, state) = visitor.{t.name} x state continue_fold in")
+  print(f"  let state = visitor.{t.name}_post_state x new_x state in")
+  print("  (new_x, state)")
+  print("")
+  for c in t.ctorsOrFields:
+    print(f"and fold_{t.name}_{c.name} : type state . state fold_config -> {c.type_} -> state -> ({c.newType} * state) = fun visitor x state ->")
+    print("  let continue_fold : state continue_fold = mk_continue_fold visitor in")
+    print(f"  visitor.{t.name}_{c.name} x state continue_fold")
+    print("")
+
+print("let no_op : 'a fold_config = {")
+for t in adts:
+  print(f"  {t.name} = (fun v state continue ->")
+  print("    match v with")
+  if t.isVariant:
+    for c in t.ctorsOrFields:
+      print(f"    | {c.name} v -> let (v, state) = continue.{t.name}_{c.name} v state in ({c.newName} v, state)")
+  else:
+    print("      {", end=' ')
+    for f in t.ctorsOrFields:
+      print(f"{f.name};", end=' ')
+    print("} ->")
+    for f in t.ctorsOrFields:
+      print(f"      let ({f.newName}, state) = continue.{t.name}_{f.name} {f.name} state in")
+    print("      ({", end=' ')
+    for f in t.ctorsOrFields:
+      print(f"{f.newName};", end=' ')
+    print("}, state)")
+  print("  );")
+  print(f"  {t.name}_pre_state = (fun v state -> ignore v; state) ;")
+  print(f"  {t.name}_post_state = (fun v new_v state -> ignore (v, new_v); state) ;")
+  for c in t.ctorsOrFields:
+    print(f"  {t.name}_{c.name} = (fun v state continue ->", end=' ')
+    if c.isBuiltin:
+      print("ignore continue; (v, state)", end=' ')
+    else:
+      print(f"continue.{c.type_} v state", end=' ')
+    print(") ;")
+print("}")
diff --git a/src/stages/adt_generator/use_a_fold.ml b/src/stages/adt_generator/use_a_fold.ml
new file mode 100644
index 000000000..6a73f4782
--- /dev/null
+++ b/src/stages/adt_generator/use_a_fold.ml
@@ -0,0 +1,48 @@
+open A
+open Fold
+
+(* TODO: how should we plug these into our test framework? *)
+
+let () =
+  let some_root : root = A { a1 = X (A { a1 = X (B 1) ; a2 = W () ; }) ; a2 = Z (W ()) ; } in
+  let op = {
+      no_op with
+      a = fun the_a state continue_fold ->
+          let (a1' , state') = continue_fold.ta1 the_a.a1 state in
+          let (a2' , state'') = continue_fold.ta2 the_a.a2 state' in
+          ({
+              a1' = a1' ;
+              a2' = a2' ;
+            }, state'' + 1)
+    } in
+  let state = 0 in
+  let (_, state) = fold_root op some_root state in
+  if state != 2 then
+    failwith (Printf.sprintf "Test failed: expected folder to count 2 nodes, but it counted %d nodes" state)
+  else
+    ()
+
+let () =
+  let some_root : root = A { a1 = X (A { a1 = X (B 1) ; a2 = W () ; }) ; a2 = Z (W ()) ; } in
+  let op = { no_op with a_pre_state = fun _the_a state -> state + 1 } in
+  let state = 0 in
+  let (_, state) = fold_root op some_root state in
+  if state != 2 then
+    failwith (Printf.sprintf "Test failed: expected folder to count 2 nodes, but it counted %d nodes" state)
+  else
+    ()
+
+let () =
+  let some_root : root = A { a1 = X (A { a1 = X (B 1) ; a2 = W () ; }) ; a2 = Z (W ()) ; } in
+  let op = { no_op with a_post_state = fun _the_a _new_a state -> state + 1 } in
+  let state = 0 in
+  let (_, state) = fold_root op some_root state in
+  if state != 2 then
+    failwith (Printf.sprintf "Test failed: expected folder to count 2 nodes, but it counted %d nodes" state)
+  else
+    ()
+
+
+(* Test that the same fold_config can be ascibed with different 'a type arguments *)
+let _noi : int fold_config = no_op (* (fun _ -> ()) *)
+let _nob : bool fold_config = no_op (* (fun _ -> ()) *)