tests for automatic fold generator + fold_config hook to update the state before a node has been transformed, without transforming it.

src/stages/adt_generator/fold.ml

@@ -36,19 +36,23 @@ type 'state continue_fold =
 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) ;
@@ -74,6 +78,7 @@ let rec mk_continue_fold : type state . state fold_config -> state continue_fold
 
 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)
@@ -92,6 +97,7 @@ and fold_root_C : type state . state fold_config -> string -> state -> (string *
 
 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)
@@ -106,6 +112,7 @@ and fold_a_a2 : type state . state fold_config -> ta2 -> state -> (ta2' * state)
 
 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)
@@ -120,6 +127,7 @@ and fold_ta1_Y : type state . state fold_config -> ta2 -> state -> (ta2' * state
 
 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)
@@ -139,6 +147,7 @@ let no_op : 'a fold_config = {
     | 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) ) ;
@@ -150,6 +159,7 @@ let no_op : 'a fold_config = {
       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 ) ;
@@ -158,6 +168,7 @@ let no_op : 'a fold_config = {
     | 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 ) ;
@@ -166,6 +177,7 @@ let no_op : 'a fold_config = {
     | 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) ) ;

src/stages/adt_generator/generator.py

@@ -72,6 +72,7 @@ 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) ;")
@@ -91,6 +92,7 @@ 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)")
@@ -120,6 +122,7 @@ for t in adts:
       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=' ')

src/stages/adt_generator/use_a_fold.ml

@@ -1,7 +1,9 @@
 open A
 open Fold
 
-let _ =
+(* 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
@@ -15,8 +17,32 @@ let _ =
     } in
   let state = 0 in
   let (_, state) = fold_root op some_root state in
-  Printf.printf "trilili %d" state
+  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 _ -> ()) *)