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A name an as bound is refused as itself when assigned, in the program and in a stopped frame alike.

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This commit is contained in:
Joseph Ferano 2026-09-26 18:16:13 +07:00
parent 83bb65957d
commit d6c33928f5
7 changed files with 87 additions and 25 deletions
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48
lib/check.ml
View File

@ -834,6 +834,8 @@ type ctx = {
here rather than recovered later because this scope list is the only place
that ever knows it. *)
mutable slot_names : string option list;
(* The slots an [as] bound in this function: [Tast.fn.as_slots]. *)
mutable as_slots : int list;
mutable scope : (string * binding) list; (* innermost first *)
(* Deferred forms, most recently registered first — which is also the order
they run in. [defer] is function-scoped, so this list belongs to the
@ -3184,6 +3186,10 @@ let unnarrowable_in (body : Ast.expr list) =
List.iter (walk ~in_fn:false) body;
!out
(* The [bwhat] of a name an [as] bound (decision 136), for the refusal to
assign it. *)
let as_tag = "~as"
let local_of loc (b : binding) =
if b.bwhat = Some narrowed_tag then
mk loc b.bty (Tast.Field (mk loc (Types.Option b.bty) (Tast.Local b.slot), 1))
@ -4919,7 +4925,7 @@ let thick_thunk env loc ps r =
env.lifted <-
{ Tast.name; params = ps;
slots = Array.of_list (ps @ [ fty ]);
snames = Array.make (n + 1) None;
snames = Array.make (n + 1) None; as_slots = [];
ret = r; body = [ mk loc r (Tast.CallPtr (callee, args)) ];
fdefers = []; fenv = Some n; fparent = Some "<thick>"; floc = loc }
:: env.lifted;
@ -5277,7 +5283,7 @@ let with_recovery env ~on f =
end
let invented_ctx env ret =
{ env; ret; lits = None; slots = 0; slot_tys = []; slot_names = []; scope = [];
{ env; ret; lits = None; slots = 0; slot_tys = []; slot_names = []; as_slots = []; scope = [];
defers = []; defer_slot = None; outer = []; outer_what = None; caught = []; place_ok = false; envslot = None; parent = None; in_frames = None; loops = []; tail = false; used = false; kept = [];
in_defer = false; defer_ok = false; defer_block = "a nested form";
owner = "<none>" }
@ -5337,7 +5343,7 @@ let condition_desc ctx loc name =
ctx.env.lifted <-
{ Tast.name = fname; params = [ Types.Ptr (Types.Mut, ty) ];
slots = Array.of_list (List.rev hctx.slot_tys);
snames = Array.of_list (List.rev hctx.slot_names);
snames = Array.of_list (List.rev hctx.slot_names); as_slots = hctx.as_slots;
ret = Types.Unit; body; fdefers = [];
fenv = None; fparent = Some ctx.owner; floc = loc }
:: ctx.env.lifted;
@ -5457,7 +5463,7 @@ and struct_key_pair env loc n =
The body is filled in below; nothing can call these in between. *)
let placeholder name ret params =
{ Tast.name; params; slots = Array.of_list params;
snames = Array.make (List.length params) None;
snames = Array.make (List.length params) None; as_slots = [];
ret; body = []; fdefers = []; fenv = None; fparent = None; floc = loc }
in
env.lifted <-
@ -5540,7 +5546,7 @@ and struct_key_pair env loc n =
let finish name ret params ctx body =
{ Tast.name; params;
slots = Array.of_list (List.rev ctx.slot_tys);
snames = Array.of_list (List.rev ctx.slot_names);
snames = Array.of_list (List.rev ctx.slot_names); as_slots = ctx.as_slots;
ret; body; fdefers = []; fenv = None; fparent = None; floc = loc }
in
env.lifted <-
@ -5588,7 +5594,7 @@ and array_key_pair env loc n e =
let eparams = [ pty; pty; Types.Int Types.I64 ] in
let placeholder name ret params =
{ Tast.name; params; slots = Array.of_list params;
snames = Array.make (List.length params) None;
snames = Array.make (List.length params) None; as_slots = [];
ret; body = []; fdefers = []; fenv = None; fparent = None; floc = loc }
in
env.lifted <-
@ -5663,7 +5669,7 @@ and array_key_pair env loc n e =
let finish name ret params ctx body =
{ Tast.name; params;
slots = Array.of_list (List.rev ctx.slot_tys);
snames = Array.of_list (List.rev ctx.slot_names);
snames = Array.of_list (List.rev ctx.slot_names); as_slots = ctx.as_slots;
ret; body; fdefers = []; fenv = None; fparent = None; floc = loc }
in
env.lifted <-
@ -7321,7 +7327,7 @@ and check_fn ctx ~want ?gen loc (params : string list) body =
let lifted =
{ Tast.name = fname; params = pts;
slots = Array.of_list (List.rev fctx.slot_tys);
snames = Array.of_list (List.rev fctx.slot_names);
snames = Array.of_list (List.rev fctx.slot_names); as_slots = fctx.as_slots;
ret; body = prefix fbody; fdefers = [];
fenv; fparent = Some ctx.owner; floc = loc }
in
@ -7444,7 +7450,7 @@ and check_handler_bind ctx ?want ?(what = "handler-bind") loc clauses body =
let lifted =
{ Tast.name = fname; params = [ Types.Ptr (Types.Mut, ty) ];
slots = Array.of_list (List.rev hctx.slot_tys);
snames = Array.of_list (List.rev hctx.slot_names);
snames = Array.of_list (List.rev hctx.slot_names); as_slots = hctx.as_slots;
ret = Types.Unit; body = prefix hbody; fdefers = [];
fenv; fparent = Some ctx.owner; floc = c.Ast.hloc }
in
@ -10830,7 +10836,8 @@ and as_cond ctx (c : Ast.expr) =
its payload copied into [g]'s once the test holds. *)
let bound ty =
scoped ctx (fun () ->
let slot = bind ctx g ty ~assignable:false in
let slot = bind ctx ~what:as_tag g ty ~assignable:false in
ctx.as_slots <- slot :: ctx.as_slots;
let b = Option.get (lookup ctx g) in
incr held_n;
named := (g, Printf.sprintf "~as%d" !held_n, b) :: !named;
@ -11318,7 +11325,7 @@ and struct_of ctx (target : Ast.expr) (t : Tast.expr) : Tast.expr * string =
"%s is tested with %s? above, so here it is what the Option \
holds, %s, and %s has no fields"
n n (tyname target.Ast.loc other) (tyname target.Ast.loc other)
| Some { bwhat = Some w; _ } ->
| Some { bwhat = Some w; _ } when w <> as_tag ->
fail target.Ast.loc
"%s is %s — the pattern bound it to %s, so the value is already \
in hand and there is no field left to read"
@ -11402,6 +11409,11 @@ and check_place ?(store = true) ctx loc (p : Ast.place) : Tast.place * Types.t =
(match List.assoc_opt name ctx.caught with
| Some (_, slot) when slot = b.slot -> captured_set ctx loc name
| _ -> ());
if b.bwhat = Some as_tag then
fail loc
"%s names what an as test found, and it cannot be given a new \
value. To change it, copy it into a local first: let %s2 = %s"
name name name;
fail loc
"%s is a parameter, and a parameter is not assignable — bind a \
local with let" name
@ -17172,7 +17184,7 @@ and trial ctx f =
Only [Loc.Error] is caught. A timeout or a stack overflow is not a
refusal to reconsider, and silently continuing past one would turn a
resource failure into a wrong answer. *)
let[@warning "+9"] { env = _; ret = _; lits = _; slots; slot_tys; slot_names; scope;
let[@warning "+9"] { env = _; ret = _; lits = _; slots; slot_tys; slot_names; as_slots; scope;
defers; defer_slot; defer_ok; defer_block; outer = _;
outer_what; caught; place_ok; envslot; parent = _;
in_frames; loops; tail; used; kept; in_defer;
@ -17183,7 +17195,7 @@ and trial ctx f =
| exception Loc.Error d ->
undo ();
ctx.slots <- slots; ctx.slot_tys <- slot_tys;
ctx.slot_names <- slot_names; ctx.scope <- scope;
ctx.slot_names <- slot_names; ctx.as_slots <- as_slots; ctx.scope <- scope;
ctx.defers <- defers; ctx.defer_slot <- defer_slot;
ctx.defer_ok <- defer_ok; ctx.defer_block <- defer_block;
ctx.outer_what <- outer_what; ctx.in_frames <- in_frames;
@ -18960,7 +18972,7 @@ let rec check_fn ?sign env (fn : Ast.fn) : Tast.fn =
let checked =
{ Tast.name = fn.Ast.name; params;
slots = Array.of_list (List.rev ctx.slot_tys);
snames = Array.of_list (List.rev ctx.slot_names);
snames = Array.of_list (List.rev ctx.slot_names); as_slots = ctx.as_slots;
(* The same defers again, for the transfer exit path §5 describes. The
normal path has them spliced into [body] above; this one is guarded on
the count, because a transfer can start above a defer that the text has
@ -19591,7 +19603,7 @@ let lift_ginit ctx loc n ty (v : Tast.expr) =
ctx.env.lifted <-
{ Tast.name = fname; params = [];
slots = Array.of_list (List.rev ctx.slot_tys);
snames = Array.of_list (List.rev ctx.slot_names);
snames = Array.of_list (List.rev ctx.slot_names); as_slots = ctx.as_slots;
(* An initialiser is a nested form as far as [defer_ok] is concerned, so
nothing can register one here and both of these are empty. Written the
same way [check_fn] writes them anyway, so that the day the rule
@ -20772,13 +20784,15 @@ let expressions env (es : (Types.t option * Ast.expr) list) :
expression's own frame, and which slot is answered beside the name, so the
caller can point every use of it at the stopped frame's storage instead
([Tast.rewrite_locals]). *)
let expression_in_scope env ~(scope : (string * Types.t * bool) list)
let expression_in_scope env ~(scope : (string * Types.t * bool * bool) list)
(e : Ast.expr) :
Tast.expr * Types.t array * string option array * (string * int) list =
let ctx = invented_ctx env Types.Unit in
let bound =
List.map
(fun (name, ty, assignable) -> (name, bind ctx name ty ~assignable))
(fun (name, ty, assignable, by_as) ->
let what = if by_as then Some as_tag else None in
(name, bind ctx ?what name ty ~assignable:(assignable && not by_as)))
scope
in
let t = expect ctx e.Ast.loc ~want:None (check ctx e) in

2
lib/emit.ml
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@ -4876,7 +4876,7 @@ let emit_startup m ?(hidden = false) (globals : Tast.global list) =
own to live in. *)
List.iter (emit_global m ~hidden) flags;
emit_fn m ~hidden
{ Tast.name = ".init-globals"; params = []; slots = [||]; snames = [||];
{ Tast.name = ".init-globals"; params = []; slots = [||]; snames = [||]; as_slots = [];
ret = Types.Unit; body; fdefers = []; fenv = None; fparent = None;
floc = (List.hd computed).Tast.ginit.Tast.loc };
true

16
lib/session.ml
View File

@ -1371,7 +1371,7 @@ let eval ?(origin = "<eval>") ?base ?forms ?pause ?(step = false) ?(running = tr
{ Tast.name = Printf.sprintf "install/%d" t.thunks;
params = []; ret = Types.Unit; body;
fdefers = []; fenv = None; fparent = None; floc = loc;
slots = [||]; snames = [||] }
slots = [||]; snames = [||]; as_slots = [] }
in
let ir =
match run_thunk with
@ -2122,7 +2122,8 @@ let write_slot ?(origin = "<set>") t ~frame ~(fn : Tast.fn) ~slot ~path
scratch and have none to keep. *)
snames =
Array.append bnames
(Array.make (List.length !extra) None) }
(Array.make (List.length !extra) None);
as_slots = [] }
in
(* A struct copy the values named first, laid out in this
module and kept, as [eval_expr] keeps one. *)
@ -2258,7 +2259,8 @@ let arm_restart ?(origin = "<restart>") t ~index ~(params : Types.t list)
@ [ nullary "flan/dev-end" ];
fdefers = []; fenv = None; fparent = None; floc = loc;
slots = Array.append base (Array.of_list (List.rev !extra));
snames = Array.append bnames (Array.make (List.length !extra) None) }
snames = Array.append bnames (Array.make (List.length !extra) None);
as_slots = [] }
in
let copies = Check.fresh_copies t.env t.program.Tast.structs in
let program =
@ -2310,7 +2312,10 @@ let in_frame t ~frame:(index, (fn : Tast.fn), bound) (parsed : Ast.expr) =
@ List.filter (fun (i, _) -> List.mem i bound) named
in
let scope =
List.map (fun (i, name) -> (name, fn.Tast.slots.(i), i >= nparams)) order
List.map
(fun (i, name) ->
(name, fn.Tast.slots.(i), i >= nparams, List.mem i fn.Tast.as_slots))
order
in
let checked, base, bnames, syn = Check.expression_in_scope t.env ~scope parsed in
let table = List.map2 (fun (i, name) (_, j) -> (j, (i, name))) order syn in
@ -2436,7 +2441,8 @@ let eval_expr ?(origin = "<eval>") ?(pause = false) ?frame t src : change =
slots = Array.append base (Array.of_list (List.rev !extra));
(* The expression's own [let]s keep their names; the slots [render] added
behind them are the walk's own scratch and have none to keep. *)
snames = Array.append bnames (Array.make (List.length !extra) None) }
snames = Array.append bnames (Array.make (List.length !extra) None);
as_slots = [] }
in
(* Built against the program but never spliced into it: an evaluation is not
a declaration, and adding one would leave the session carrying an eval/N

4
lib/tast.ml
View File

@ -354,6 +354,10 @@ type fn = {
backend is free to ignore it entirely -- nothing is *resolved* through it,
and a slot is still only ever referred to by index. *)
snames : string option array;
(* The slots an [as] bound (decision 136): named, and read-only, so
evaluating in a stopped frame may read them and may not assign them,
as the program itself may not. *)
as_slots : int list;
ret : Types.t;
body : expr list;
(* The defers again, innermost first. [body] already has them spliced onto

31
test/test_dev.ml
View File

@ -2533,7 +2533,36 @@ let () =
(match List.assoc_opt "e" rows with
| Some ("dyn", v) when Test_support.contains v "hi" -> ()
| Some (ty, v) -> fail "locals show e as %s %s (%s)" ty v backend
| None -> fail "locals do not show e (%s)" backend)
| None -> fail "locals do not show e (%s)" backend);
(* Eval-in-frame reads them and, as the program may not, cannot
assign them. *)
let eval code =
ask
(Printf.sprintf "(:op \"eval-expr\" :frame 0 :code %s :syntax \"indented\")"
(Wire.quote code))
in
let r = eval "g + 1" in
if Wire.string_field r "value" <> Some "42" then
fail "eval-in-frame g + 1 (%s): %s" backend
(Option.value ~default:(status r) (Wire.string_field r "message"));
List.iter
(fun (code, name) ->
let r = eval code in
if status r = "ok" then
fail "eval-in-frame %s was accepted (%s)" code backend
else if
not
(Test_support.contains
(Option.value ~default:"" (Wire.string_field r "message"))
(name ^ " names what an as test found"))
then
fail "eval-in-frame %s (%s) said: %s" code backend
(Option.value ~default:"" (Wire.string_field r "message")))
[ ("g = 7", "g"); ("e = 1", "e") ];
let r = eval "g" in
if Wire.string_field r "value" <> Some "41" then
fail "g changed after a refused assignment (%s): %s" backend
(Option.value ~default:(status r) (Wire.string_field r "value"))
end;
ignore (ask "(:op \"close\")");
Unix.close c;

9
test/test_flan.ml
View File

@ -1507,6 +1507,15 @@ let () =
refuses_all ~fln:true "~~ in .fln" "fn f(a: bool) -> i32\n ~~a\n" "~~ works on the bits";
refuses_all ~fln:true "^^ in .fln" "fn f(a: bool, b: bool) -> bool\n a ^^ b == 0\n"
"write a != b";
(* A name an as bound is read-only, and says so as itself, not as a
parameter (decision 136). *)
refuses_all ~fln:true "assigning an as name"
"fn f(o: i32?, d) -> i32\n if o as g and d as e\n g = 5\n g\n else\n 0\n"
"g names what an as test found, and it cannot be given a new value. To \
change it, copy it into a local first: let g2 = g";
refuses_all ~fln:true "assigning a dyn as name"
"fn f(o: i32?, d) -> i32\n if o as g and d as e\n e = 5\n g\n else\n 0\n"
"e names what an as test found";
rejects_check "popcount of a float"
"(defn f [a f64] f64 (popcount a))" ~needle:"popcount takes integers, found f64";
rejects_check "a rotation's count does not widen the value"

2
test/test_session.ml
View File

@ -1805,7 +1805,7 @@ let () =
{ Tast.name = "f"; params = []; ret = Types.Unit; body = [];
fdefers = []; fenv = None; fparent = None; floc = Loc.unknown;
slots = Array.make (Array.length snames) (Types.Int Types.I32);
snames }
snames; as_slots = [] }
in
(match Session.shown_names (fn [| Some "k~2"; None |]) with
| [| Some "k"; None |] -> ()