diff --git a/docker/distribution/generic/build.Dockerfile b/docker/distribution/generic/build.Dockerfile
index f6c9358e9..ba01c043c 100644
--- a/docker/distribution/generic/build.Dockerfile
+++ b/docker/distribution/generic/build.Dockerfile
@@ -29,7 +29,7 @@ RUN opam update
 
 # Install ligo
 RUN sh scripts/install_vendors_deps.sh
-RUN opam install -y .
+RUN opam install -y . || (tail -n +1 ~/.opam/log/* ; false)
 
 # Use the ligo binary as a default command
 ENTRYPOINT [ "/home/opam/.opam/4.07/bin/ligo" ]
diff --git a/scripts/build_docker_image.sh b/scripts/build_docker_image.sh
index 260a530c7..f342b424f 100755
--- a/scripts/build_docker_image.sh
+++ b/scripts/build_docker_image.sh
@@ -1,3 +1,4 @@
 #!/bin/sh
 set -e
-docker build -t "${LIGO_REGISTRY_IMAGE_BUILD:-ligolang/ligo}:next" -f ./docker/distribution/debian/distribute.Dockerfile .
\ No newline at end of file
+set -x
+docker build -t "${LIGO_REGISTRY_IMAGE_BUILD:-ligolang/ligo}:next" -f ./docker/distribution/debian/distribute.Dockerfile .
diff --git a/scripts/build_ligo_local.sh b/scripts/build_ligo_local.sh
index b78e4ffd6..fb556805a 100755
--- a/scripts/build_ligo_local.sh
+++ b/scripts/build_ligo_local.sh
@@ -1,5 +1,6 @@
 #!/bin/sh
 set -e
+set -x
 
 eval $(opam config env)
 dune build -p ligo
diff --git a/scripts/distribution/generic/build.sh b/scripts/distribution/generic/build.sh
index 49aba15e1..968f55a21 100755
--- a/scripts/distribution/generic/build.sh
+++ b/scripts/distribution/generic/build.sh
@@ -1,4 +1,6 @@
 #!/bin/sh
+set -e
+set -x
 
 dockerfile_name="build"
 # Generic dockerfile
diff --git a/scripts/distribution/generic/package.sh b/scripts/distribution/generic/package.sh
index 79be37d41..d9d047e6d 100755
--- a/scripts/distribution/generic/package.sh
+++ b/scripts/distribution/generic/package.sh
@@ -1,4 +1,6 @@
 #!/bin/sh
+set -e
+set -x
 
 dockerfile_name="package"
 dockerfile=""
diff --git a/scripts/distribution/generic/parameters.sh b/scripts/distribution/generic/parameters.sh
index 3899711d8..2241b9fb0 100644
--- a/scripts/distribution/generic/parameters.sh
+++ b/scripts/distribution/generic/parameters.sh
@@ -1,11 +1,15 @@
+#!/bin/sh
+set -e
+set -x
+
 # This script accepts three arguments, os family, os and its version,
 # which are subsequently used to fetch the respective docker
 # image from the ocaml/infrastructure project.
 #
 # https://github.com/ocaml/infrastructure/wiki/Containers#selecting-linux-distributions
-target_os_family=$1
-target_os=$2
-target_os_version=$3
+target_os_family="$1"
+target_os="$2"
+target_os_version="$3"
 
 # Variables configured at the CI level
 dist="$LIGO_DIST_DIR"
@@ -29,4 +33,4 @@ fi
 target_os_specific_dockerfile="./docker/distribution/$target_os_family/$target_os/$dockerfile_name.Dockerfile"
 if test -f "$target_os_specific_dockerfile"; then
     dockerfile="$target_os_specific_dockerfile"
-fi
\ No newline at end of file
+fi
diff --git a/scripts/install_build_environment.sh b/scripts/install_build_environment.sh
index 0dd33f068..628235e70 100755
--- a/scripts/install_build_environment.sh
+++ b/scripts/install_build_environment.sh
@@ -22,6 +22,7 @@ echo "Installing dependencies.."
 if [ -n "`uname -a | grep -i arch`" ]
 then
     sudo pacman -Sy --noconfirm \
+        python \
         make \
         m4 \
         gcc \
@@ -34,6 +35,8 @@ fi
 if [ -n "`uname -a | grep -i ubuntu`" ]
 then
 sudo apt-get install -y make \
+     python3 \
+     make \
      m4 \
      gcc \
      patch \
diff --git a/scripts/install_native_dependencies.sh b/scripts/install_native_dependencies.sh
index 2a0e56903..f12e76cb2 100755
--- a/scripts/install_native_dependencies.sh
+++ b/scripts/install_native_dependencies.sh
@@ -1,11 +1,13 @@
 #!/bin/sh
 set -e
+set -x
 . /etc/os-release
 
 if [ $ID = arch ]
 then
     pacman -Sy
     sudo pacman -S --noconfirm \
+        python \
         libevdev \
         perl \
         pkg-config \
@@ -20,6 +22,7 @@ then
 else
     apt-get update -qq
     apt-get -y -qq install \
+        python3 \
         libev-dev \
         perl \
         pkg-config \
diff --git a/scripts/install_vendors_deps.sh b/scripts/install_vendors_deps.sh
index 15f9b47d4..5c870ffdc 100755
--- a/scripts/install_vendors_deps.sh
+++ b/scripts/install_vendors_deps.sh
@@ -1,5 +1,6 @@
 #!/bin/sh
 set -e
+set -x
 
 # Install local dependencies
 opam install -y --deps-only --with-test ./ligo.opam $(find vendors -name \*.opam)
diff --git a/src/passes/4-typer-old/typer.ml b/src/passes/4-typer-old/typer.ml
index 87f4b2477..7c1cd41a4 100644
--- a/src/passes/4-typer-old/typer.ml
+++ b/src/passes/4-typer-old/typer.ml
@@ -649,7 +649,6 @@ and type_expression' : environment -> ?tv_opt:O.type_expression -> I.expression
           let wtype = Format.asprintf
             "Loops over collections expect lists, sets or maps, got type %a" O.PP.type_expression tv_col in 
           fail @@ simple_error wtype in 
-      let lname = lname in
       let e' = Environment.add_ez_binder lname input_type e in
       let%bind body = type_expression' ?tv_opt:(Some tv_out) e' result in
       let output_type = body.type_expression in
diff --git a/src/stages/adt_generator/.gitignore b/src/stages/adt_generator/.gitignore
new file mode 100644
index 000000000..9ec2ad34e
--- /dev/null
+++ b/src/stages/adt_generator/.gitignore
@@ -0,0 +1,2 @@
+# This is an auto-generated test file
+/generated_fold.ml
diff --git a/src/stages/adt_generator/README b/src/stages/adt_generator/README
index 20ecdfd43..2d1b53c3d 100644
--- a/src/stages/adt_generator/README
+++ b/src/stages/adt_generator/README
@@ -1,6 +1,6 @@
-Build with:
+Build & test with:
 
-    dune build adt_generator.a
+    dune build adt_generator.exe && ../../../_build/default/src/stages/adt_generator/adt_generator.exe
 
 Run with
 
diff --git a/src/stages/adt_generator/a.ml b/src/stages/adt_generator/a.ml
index f1d8b2fb1..34b611dc1 100644
--- a/src/stages/adt_generator/a.ml
+++ b/src/stages/adt_generator/a.ml
@@ -1,6 +1,6 @@
 type root =
-| A of a
-| B of int
+| A of rootA
+| B of rootB
 | C of string
 
 and a = {
@@ -15,3 +15,20 @@ and ta1 =
 and ta2 =
 | Z of ta2
 | W of unit
+
+and rootA =
+  a list
+
+and rootB =
+  int list
+
+let fold_list v state continue =
+  let aux = fun (lst', state) elt ->
+    let (elt', state) = continue elt state in
+    (elt' :: lst' , state) in
+  List.fold_left aux ([], state) v
+
+let fold_option v state continue =
+  match v with
+    Some x -> continue x state
+  | None -> None
diff --git a/src/stages/adt_generator/dune b/src/stages/adt_generator/dune
index 4a52c6088..d70d8647e 100644
--- a/src/stages/adt_generator/dune
+++ b/src/stages/adt_generator/dune
@@ -1,8 +1,9 @@
 (rule
-  (target fold.ml)
+  (target generated_fold.ml)
   (deps generator.py)
-  (action (with-stdout-to fold.ml (run python3 ./generator.py)))
-  (mode (promote (until-clean))))
+  (action (with-stdout-to generated_fold.ml (run python3 ./generator.py)))
+;  (mode (promote (until-clean))) ; If this is uncommented, then "dune build -p ligo" can't find the file (but "dune build" can)
+)
 ; (library
 ;   (name adt_generator)
 ;   (public_name ligo.adt_generator)
@@ -16,3 +17,8 @@
   (libraries
   )
 )
+
+(alias
+  (name runtest)
+  (action (run ./adt_generator.exe))
+)
diff --git a/src/stages/adt_generator/fold.ml b/src/stages/adt_generator/fold.ml
index 4e4c41357..271974820 100644
--- a/src/stages/adt_generator/fold.ml
+++ b/src/stages/adt_generator/fold.ml
@@ -1,184 +1 @@
-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) ) ;
-}
+include Generated_fold
diff --git a/src/stages/adt_generator/generator.py b/src/stages/adt_generator/generator.py
index 65fe21878..48b8c5fd4 100644
--- a/src/stages/adt_generator/generator.py
+++ b/src/stages/adt_generator/generator.py
@@ -1,34 +1,49 @@
 moduleName = "A"
+variant="_ _variant"
+record="_ _record"
+def poly(x): return x
 adts = [
-  # typename, variant?, fields_or_ctors
-  ("root", True, [
-      # ctor, builtin, type
-      ("A", False, "a"),
-      ("B", True, "int"),
+  # typename, kind, fields_or_ctors
+  ("root", variant, [
+      # ctor, builtin?, type
+      ("A", False, "rootA"),
+      ("B", False, "rootB"),
       ("C", True, "string"),
   ]),
-  ("a", False, [
+  ("a", record, [
+    # field, builtin?, type
     ("a1", False, "ta1"),
     ("a2", False, "ta2"),
   ]),
-  ("ta1", True, [
+  ("ta1", variant, [
       ("X", False, "root"),
       ("Y", False, "ta2"),
   ]),
-  ("ta2", True, [
+  ("ta2", variant, [
       ("Z", False, "ta2"),
       ("W", True, "unit"),
   ]),
+  # polymorphic type
+  ("rootA", poly("list"),
+   [
+    # Position (0..n-1), builtin?, type argument
+    (0, False, "a")
+  ]),
+  ("rootB", poly("list"),
+   [
+    # Position (0..n-1), builtin?, type argument
+    (0, True, "int")
+  ]),
 ]
 
 from collections import namedtuple
-adt = namedtuple('adt', ['name', 'newName', 'isVariant', 'ctorsOrFields'])
+adt = namedtuple('adt', ['name', 'newName', 'kind', 'ctorsOrFields'])
 ctorOrField = namedtuple('ctorOrField', ['name', 'newName', 'isBuiltin', 'type_', 'newType'])
 adts = [
   adt(
     name = name,
     newName = f"{name}'",
-    isVariant = isVariant,
+    kind = kind,
     ctorsOrFields = [
       ctorOrField(
         name = cf,
@@ -40,23 +55,32 @@ adts = [
       for (cf, isBuiltin, type_) in ctors
     ],
   )
-  for (name, isVariant, ctors) in adts
+  for (name, kind, ctors) in adts
 ]
 
+print("(* This is an auto-generated file. Do not edit. *)")
+
+print("")
 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:
+  if t.kind == variant:
     for c in t.ctorsOrFields:
       print(f"  | {c.newName} of {c.newType}")
-  else:
+  elif t.kind == record:
     print("  {")
     for f in t.ctorsOrFields:
       print(f"    {f.newName} : {f.newType} ;")
     print("  }")
+  else:
+    print("  ", end='')
+    for a in t.ctorsOrFields:
+      print(f"{a.newType}", end=' ')
+    print(t.kind, end='')
+    print("")
 
 print("")
 print(f"type 'state continue_fold =")
@@ -107,10 +131,10 @@ 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:
+  if t.kind == variant:
     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:
+  elif t.kind == record:
     print("      {", end=' ')
     for f in t.ctorsOrFields:
       print(f"{f.name};", end=' ')
@@ -121,6 +145,10 @@ for t in adts:
     for f in t.ctorsOrFields:
       print(f"{f.newName};", end=' ')
     print("}, state)")
+  else:
+    print(f"      v -> fold_{t.kind} v state (", end=' ')
+    print(", ".join([f"continue.{t.name}_{f.name}" for f in t.ctorsOrFields]), end='')
+    print(" )")
   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) ;")
diff --git a/src/stages/adt_generator/use_a_fold.ml b/src/stages/adt_generator/use_a_fold.ml
index 6a73f4782..0fe476d42 100644
--- a/src/stages/adt_generator/use_a_fold.ml
+++ b/src/stages/adt_generator/use_a_fold.ml
@@ -4,7 +4,7 @@ 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 some_root : root = A [{ a1 = X (A [{ a1 = X (B [1;2;3]) ; a2 = W () ; }]) ; a2 = Z (W ()) ; }] in
   let op = {
       no_op with
       a = fun the_a state continue_fold ->
@@ -23,7 +23,7 @@ let () =
     ()
 
 let () =
-  let some_root : root = A { a1 = X (A { a1 = X (B 1) ; a2 = W () ; }) ; a2 = Z (W ()) ; } in
+  let some_root : root = A [{ a1 = X (A [{ a1 = X (B [1;2;3]) ; 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
@@ -33,7 +33,7 @@ let () =
     ()
 
 let () =
-  let some_root : root = A { a1 = X (A { a1 = X (B 1) ; a2 = W () ; }) ; a2 = Z (W ()) ; } in
+  let some_root : root = A [{ a1 = X (A [{ a1 = X (B [1;2;3]) ; 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
diff --git a/src/stages/ast_typed/types.ml b/src/stages/ast_typed/types.ml
index 5aa323c9b..8804e49e7 100644
--- a/src/stages/ast_typed/types.ml
+++ b/src/stages/ast_typed/types.ml
@@ -95,7 +95,6 @@ and matching =
 
 and ascription = {anno_expr: expression; type_annotation: type_expression}
 
-
 and environment_element_definition =
   | ED_binder
   | ED_declaration of (expression * free_variables)
diff --git a/tools/webide/Dockerfile b/tools/webide/Dockerfile
index 4dfa9963a..212b12130 100644
--- a/tools/webide/Dockerfile
+++ b/tools/webide/Dockerfile
@@ -17,7 +17,7 @@ FROM node:12-buster
 
 WORKDIR /app
 
-RUN apt-get update && apt-get -y install libev-dev perl pkg-config libgmp-dev libhidapi-dev m4 libcap-dev bubblewrap rsync
+RUN apt-get update && apt-get -y install python3 libev-dev perl pkg-config libgmp-dev libhidapi-dev m4 libcap-dev bubblewrap rsync
 
 COPY ligo_deb10.deb /tmp/ligo_deb10.deb
 RUN dpkg -i /tmp/ligo_deb10.deb && rm /tmp/ligo_deb10.deb
diff --git a/vendors/UnionFind/UnionFind.install b/vendors/UnionFind/UnionFind.install
deleted file mode 100644
index 692984e20..000000000
--- a/vendors/UnionFind/UnionFind.install
+++ /dev/null
@@ -1,36 +0,0 @@
-lib: [
-  "_build/install/default/lib/UnionFind/META"
-  "_build/install/default/lib/UnionFind/Partition.cmi"
-  "_build/install/default/lib/UnionFind/Partition.cmti"
-  "_build/install/default/lib/UnionFind/Partition.mli"
-  "_build/install/default/lib/UnionFind/Partition0.cmi"
-  "_build/install/default/lib/UnionFind/Partition0.cmt"
-  "_build/install/default/lib/UnionFind/Partition0.cmx"
-  "_build/install/default/lib/UnionFind/Partition0.ml"
-  "_build/install/default/lib/UnionFind/Partition1.cmi"
-  "_build/install/default/lib/UnionFind/Partition1.cmt"
-  "_build/install/default/lib/UnionFind/Partition1.cmx"
-  "_build/install/default/lib/UnionFind/Partition1.ml"
-  "_build/install/default/lib/UnionFind/Partition2.cmi"
-  "_build/install/default/lib/UnionFind/Partition2.cmt"
-  "_build/install/default/lib/UnionFind/Partition2.cmx"
-  "_build/install/default/lib/UnionFind/Partition2.ml"
-  "_build/install/default/lib/UnionFind/Partition3.cmi"
-  "_build/install/default/lib/UnionFind/Partition3.cmt"
-  "_build/install/default/lib/UnionFind/Partition3.cmx"
-  "_build/install/default/lib/UnionFind/Partition3.ml"
-  "_build/install/default/lib/UnionFind/UnionFind.a"
-  "_build/install/default/lib/UnionFind/UnionFind.cma"
-  "_build/install/default/lib/UnionFind/UnionFind.cmxa"
-  "_build/install/default/lib/UnionFind/UnionFind.cmxs"
-  "_build/install/default/lib/UnionFind/dune-package"
-  "_build/install/default/lib/UnionFind/opam"
-  "_build/install/default/lib/UnionFind/unionFind.cmi"
-  "_build/install/default/lib/UnionFind/unionFind.cmt"
-  "_build/install/default/lib/UnionFind/unionFind.cmx"
-  "_build/install/default/lib/UnionFind/unionFind.ml"
-]
-doc: [
-  "_build/install/default/doc/UnionFind/LICENSE"
-  "_build/install/default/doc/UnionFind/README.md"
-]