Remove assert as a reserved keyword

CHANGELOG.md

@@ -16,6 +16,7 @@
 
 - Make `Jsx.component` abstract. https://github.com/rescript-lang/rescript/pull/8390
 - Drop Node.js version 20.x support, as it is reaching EOL. https://github.com/rescript-lang/rescript/pull/8401
+- Remove `assert` as a reserved keyword. Since v12 `assert` is parsed as regular function. If you ran the formatter on your codebase using v12, this change is not a breaking change. https://github.com/rescript-lang/rescript/pull/8399
 
 #### :eyeglasses: Spec Compliance
 

analysis/src/DumpAst.ml

@@ -234,8 +234,6 @@ and printExprItem expr ~pos ~indentation =
     ^ "\n" ^ addIndentation indentation ^ ")"
   | Pexp_extension (({txt} as loc), _) ->
     "Pexp_extension(%" ^ (loc |> printLocDenominatorLoc ~pos) ^ txt ^ ")"
-  | Pexp_assert expr ->
-    "Pexp_assert(" ^ printExprItem expr ~pos ~indentation ^ ")"
   | Pexp_field (exp, loc) ->
     "Pexp_field("
     ^ (loc |> printLocDenominatorLoc ~pos)

analysis/src/Utils.ml

@@ -109,7 +109,6 @@ let identifyPexp pexp =
   | Pexp_send _ -> "Pexp_send"
   | Pexp_letmodule _ -> "Pexp_letmodule"
   | Pexp_letexception _ -> "Pexp_letexception"
-  | Pexp_assert _ -> "Pexp_assert"
   | Pexp_newtype _ -> "Pexp_newtype"
   | Pexp_pack _ -> "Pexp_pack"
   | Pexp_extension _ -> "Pexp_extension"

compiler/frontend/bs_ast_mapper.ml

@@ -375,7 +375,6 @@ module E = struct
       letexception ~loc ~attrs
         (sub.extension_constructor sub cd)
         (sub.expr sub e)
-    | Pexp_assert e -> assert_ ~loc ~attrs (sub.expr sub e)
     | Pexp_newtype (s, e) ->
       newtype ~loc ~attrs (map_loc sub s) (sub.expr sub e)
     | Pexp_pack me -> pack ~loc ~attrs (sub.module_expr sub me)

compiler/ml/ast_helper.ml

@@ -189,7 +189,6 @@ module Exp = struct
   let send ?loc ?attrs a b = mk ?loc ?attrs (Pexp_send (a, b))
   let letmodule ?loc ?attrs a b c = mk ?loc ?attrs (Pexp_letmodule (a, b, c))
   let letexception ?loc ?attrs a b = mk ?loc ?attrs (Pexp_letexception (a, b))
-  let assert_ ?loc ?attrs a = mk ?loc ?attrs (Pexp_assert a)
   let newtype ?loc ?attrs a b = mk ?loc ?attrs (Pexp_newtype (a, b))
   let pack ?loc ?attrs a = mk ?loc ?attrs (Pexp_pack a)
   let open_ ?loc ?attrs a b c = mk ?loc ?attrs (Pexp_open (a, b, c))

compiler/ml/ast_helper.mli

@@ -212,7 +212,6 @@ module Exp : sig
     extension_constructor ->
     expression ->
     expression
-  val assert_ : ?loc:loc -> ?attrs:attrs -> expression -> expression
   val newtype : ?loc:loc -> ?attrs:attrs -> str -> expression -> expression
   val pack : ?loc:loc -> ?attrs:attrs -> module_expr -> expression
   val open_ :

compiler/ml/ast_iterator.ml

@@ -360,7 +360,6 @@ module E = struct
     | Pexp_letexception (cd, e) ->
       sub.extension_constructor sub cd;
       sub.expr sub e
-    | Pexp_assert e -> sub.expr sub e
     | Pexp_newtype (_s, e) -> sub.expr sub e
     | Pexp_pack me -> sub.module_expr sub me
     | Pexp_open (_ovf, lid, e) ->

compiler/ml/ast_mapper.ml

@@ -344,7 +344,6 @@ module E = struct
       letexception ~loc ~attrs
         (sub.extension_constructor sub cd)
         (sub.expr sub e)
-    | Pexp_assert e -> assert_ ~loc ~attrs (sub.expr sub e)
     | Pexp_newtype (s, e) ->
       newtype ~loc ~attrs (map_loc sub s) (sub.expr sub e)
     | Pexp_pack me -> pack ~loc ~attrs (sub.module_expr sub me)

compiler/ml/ast_mapper_from0.ml

@@ -624,7 +624,11 @@ module E = struct
       letexception ~loc ~attrs
         (sub.extension_constructor sub cd)
         (sub.expr sub e)
-    | Pexp_assert e -> assert_ ~loc ~attrs (sub.expr sub e)
+    | Pexp_assert e ->
+      apply ~loc ~attrs
+        (ident ~loc
+           {txt = Longident.Ldot (Longident.Lident "Pervasives", "assert"); loc})
+        [(Asttypes.Nolabel, sub.expr sub e)]
     | Pexp_lazy _ -> failwith "Pexp_lazy is no longer present in ReScript"
     | Pexp_poly _ -> failwith "Pexp_poly is no longer present in ReScript"
     | Pexp_object () -> assert false

compiler/ml/ast_mapper_to0.ml

@@ -504,7 +504,6 @@ module E = struct
       letexception ~loc ~attrs
         (sub.extension_constructor sub cd)
         (sub.expr sub e)
-    | Pexp_assert e -> assert_ ~loc ~attrs (sub.expr sub e)
     | Pexp_newtype (s, e) ->
       newtype ~loc ~attrs (map_loc sub s) (sub.expr sub e)
     | Pexp_pack me -> pack ~loc ~attrs (sub.module_expr sub me)

compiler/ml/depend.ml

@@ -283,7 +283,6 @@ let rec add_expr bv exp =
     let b = add_module_binding bv m in
     add_expr (StringMap.add id.txt b bv) e
   | Pexp_letexception (_, e) -> add_expr bv e
-  | Pexp_assert e -> add_expr bv e
   | Pexp_newtype (_, e) -> add_expr bv e
   | Pexp_pack m -> add_module bv m
   | Pexp_open (_ovf, m, e) ->

compiler/ml/parsetree.ml

@@ -303,10 +303,6 @@ and expression_desc =
     (* let module M = ME in E *)
   | Pexp_letexception of extension_constructor * expression
     (* let exception C in E *)
-  | Pexp_assert of expression
-    (* assert E
-       Note: "assert false" is treated in a special way by the
-       type-checker. *)
   | Pexp_newtype of string loc * expression (* fun (type t) -> E *)
   | Pexp_pack of module_expr
     (* (module ME)

compiler/ml/pprintast.ml

@@ -718,7 +718,6 @@ and expression ctxt f x =
       pp f "@[<hov2>let@ exception@ %a@ in@ %a@]"
         (extension_constructor ctxt)
         cd (expression ctxt) e
-    | Pexp_assert e -> pp f "@[<hov2>assert@ %a@]" (simple_expr ctxt) e
     | Pexp_open (ovf, lid, e) ->
       pp f "@[<2>let open%s %a in@;%a@]" (override ovf) longident_loc lid
         (expression ctxt) e

compiler/ml/printast.ml

@@ -347,9 +347,6 @@ and expression i ppf x =
     line i ppf "Pexp_letexception\n";
     extension_constructor i ppf cd;
     expression i ppf e
-  | Pexp_assert e ->
-    line i ppf "Pexp_assert\n";
-    expression i ppf e
   | Pexp_newtype (s, e) ->
     line i ppf "Pexp_newtype \"%s\"\n" s.txt;
     expression i ppf e

compiler/ml/translcore.ml

@@ -457,48 +457,51 @@ let warn_polymorphic_comparison loc prim args =
 
 let transl_primitive loc p env ty =
   (* Printf.eprintf "----transl_primitive %s----\n" p.prim_name; *)
-  let prim =
-    try specialize_primitive p env ty (* ~has_constant_constructor:false *)
-    with Not_found -> Pccall p
-  in
-  warn_polymorphic_comparison loc prim [];
-  match prim with
-  | Ploc kind -> (
-    let lam = lam_of_loc kind loc in
-    match p.prim_arity with
-    | 0 -> lam
-    | 1 ->
-      (* TODO: we should issue a warning ? *)
-      let param = Ident.create "prim" in
-      Lfunction
-        {
-          params = [param];
-          attr = default_function_attribute;
-          loc;
-          body = Lprim (Pmakeblock Blk_tuple, [lam; Lvar param], loc);
-        }
-    | _ -> assert false)
-  | _ ->
-    let rec make_params n total =
-      if n <= 0 then []
-      else
-        Ident.create ("prim" ^ string_of_int (total - n))
-        :: make_params (n - 1) total
+  if p.Primitive.prim_name = "%assert" then
+    fatal_error "Translcore.transl_primitive: first-class %assert"
+  else
+    let prim =
+      try specialize_primitive p env ty (* ~has_constant_constructor:false *)
+      with Not_found -> Pccall p
     in
-    let prim_arity = p.prim_arity in
-    if p.prim_from_constructor || prim_arity = 0 then Lprim (prim, [], loc)
-    else
-      let params =
-        if prim_arity = 1 then [Ident.create "prim"]
-        else make_params prim_arity prim_arity
+    warn_polymorphic_comparison loc prim [];
+    match prim with
+    | Ploc kind -> (
+      let lam = lam_of_loc kind loc in
+      match p.prim_arity with
+      | 0 -> lam
+      | 1 ->
+        (* TODO: we should issue a warning ? *)
+        let param = Ident.create "prim" in
+        Lfunction
+          {
+            params = [param];
+            attr = default_function_attribute;
+            loc;
+            body = Lprim (Pmakeblock Blk_tuple, [lam; Lvar param], loc);
+          }
+      | _ -> assert false)
+    | _ ->
+      let rec make_params n total =
+        if n <= 0 then []
+        else
+          Ident.create ("prim" ^ string_of_int (total - n))
+          :: make_params (n - 1) total
       in
-      Lfunction
-        {
-          params;
-          attr = default_function_attribute;
-          loc;
-          body = Lprim (prim, List.map (fun id -> Lvar id) params, loc);
-        }
+      let prim_arity = p.prim_arity in
+      if p.prim_from_constructor || prim_arity = 0 then Lprim (prim, [], loc)
+      else
+        let params =
+          if prim_arity = 1 then [Ident.create "prim"]
+          else make_params prim_arity prim_arity
+        in
+        Lfunction
+          {
+            params;
+            attr = default_function_attribute;
+            loc;
+            body = Lprim (prim, List.map (fun id -> Lvar id) params, loc);
+          }
 
 let transl_primitive_application loc prim env ty args =
   let prim_name = prim.prim_name in
@@ -718,6 +721,23 @@ and transl_exp0 (e : Typedtree.expression) : Lambda.lambda =
           [lambda],
           loc )
     | None -> lambda)
+  | Texp_apply
+      {
+        funct =
+          {
+            exp_desc =
+              Texp_ident (_, _, {val_kind = Val_prim {prim_name = "%assert"}});
+          };
+        args = [(_, Some cond)];
+      } -> (
+    (* assert(cond) — same semantics as the old assert keyword *)
+    match cond.exp_desc with
+    | Texp_construct (_, {cstr_name = "false"}, _) ->
+      if !Clflags.no_assert_false then Lambda.lambda_assert_false
+      else assert_failed e
+    | _ ->
+      if !Clflags.noassert then lambda_unit
+      else Lifthenelse (transl_exp cond, lambda_unit, assert_failed e))
   | Texp_apply
       {
         funct =

compiler/ml/typecore.ml

@@ -98,6 +98,7 @@ type error =
   | Type_params_not_supported of Longident.t
   | Field_access_on_dict_type
   | Jsx_not_enabled
+  | Assert_must_be_direct_call
 
 exception Error of Location.t * Env.t * error
 exception Error_forward of Location.error
@@ -151,6 +152,11 @@ let with_depth depth_ref f =
   depth_ref := saved + 1;
   Misc.try_finally f (fun () -> depth_ref := saved)
 
+let is_assert_primitive (desc : Types.value_description) =
+  match desc.val_kind with
+  | Val_prim {Primitive.prim_name = "%assert"} -> true
+  | _ -> false
+
 let with_reset_control_flow f =
   let saved_loop_depth = !loop_depth in
   loop_depth := 0;
@@ -186,7 +192,6 @@ let iter_expression f e =
       List.iter (fun {x = e} -> expr e) iel
     | Pexp_open (_, _, e)
     | Pexp_newtype (_, e)
-    | Pexp_assert e
     | Pexp_send (e, _)
     | Pexp_constraint (e, _)
     | Pexp_coerce (e, _, _)
@@ -2371,6 +2376,8 @@ and type_expect_ ?deprecated_context ~context ?in_function ?(recarg = Rejected)
           | v -> v)
         env lid.loc lid.txt
     in
+    if is_assert_primitive desc then
+      raise (Error (loc, env, Assert_must_be_direct_call));
     (if !Clflags.annotations then
        let dloc = desc.Types.val_loc in
        let annot =
@@ -2503,6 +2510,28 @@ and type_expect_ ?deprecated_context ~context ?in_function ?(recarg = Rejected)
     type_function ?in_function ~arity ~async loc sexp.pexp_attributes env
       ty_expected l
       [Ast_helper.Exp.case spat sbody]
+  | Pexp_apply {funct = {pexp_desc = Pexp_ident lid}; args = [(Nolabel, scond)]}
+    when match Env.lookup_value lid.txt env with
+         | _, desc -> is_assert_primitive desc
+         | exception Not_found -> false ->
+    (* assert(cond) via the %assert primitive — same semantics as the keyword form *)
+    let cond =
+      type_expect ~context:(Some AssertCondition) env scond Predef.type_bool
+    in
+    let exp_type =
+      match cond.exp_desc with
+      | Texp_construct (_, {cstr_name = "false"}, _) -> instance env ty_expected
+      | _ -> instance_def Predef.type_unit
+    in
+    rue
+      {
+        exp_desc = Texp_assert cond;
+        exp_loc = loc;
+        exp_extra = [];
+        exp_type;
+        exp_attributes = sexp.pexp_attributes;
+        exp_env = env;
+      }
   | Pexp_apply {funct = sfunct; args = sargs; partial; transformed_jsx} ->
     assert (sargs <> []);
     begin_def ();
@@ -3337,24 +3366,6 @@ and type_expect_ ?deprecated_context ~context ?in_function ?(recarg = Rejected)
         exp_attributes = sexp.pexp_attributes;
         exp_env = env;
       }
-  | Pexp_assert e ->
-    let cond =
-      type_expect ~context:(Some AssertCondition) env e Predef.type_bool
-    in
-    let exp_type =
-      match cond.exp_desc with
-      | Texp_construct (_, {cstr_name = "false"}, _) -> instance env ty_expected
-      | _ -> instance_def Predef.type_unit
-    in
-    rue
-      {
-        exp_desc = Texp_assert cond;
-        exp_loc = loc;
-        exp_extra = [];
-        exp_type;
-        exp_attributes = sexp.pexp_attributes;
-        exp_env = env;
-      }
   | Pexp_newtype ({txt = name}, sbody) ->
     let ty = newvar () in
     (* remember original level *)
@@ -5012,6 +5023,10 @@ let report_error env loc ppf error =
     fprintf ppf
       "Cannot compile JSX expression because JSX support is not enabled. Add \
        \"jsx\" settings to rescript.json to enable JSX support."
+  | Assert_must_be_direct_call ->
+    fprintf ppf
+      "`assert` can only be used as a direct call like `assert(condition)`. It \
+       cannot be aliased or passed as a function."
 
 let report_error env loc ppf err =
   Printtyp.wrap_printing_env env (fun () -> report_error env loc ppf err)

compiler/ml/typecore.mli

@@ -131,6 +131,7 @@ type error =
   | Type_params_not_supported of Longident.t
   | Field_access_on_dict_type
   | Jsx_not_enabled
+  | Assert_must_be_direct_call
 
 exception Error of Location.t * Env.t * error
 exception Error_forward of Location.error

compiler/syntax/src/res_ast_debugger.ml

@@ -703,7 +703,6 @@ module SexpAst = struct
             extension_constructor ext_constr;
             expression expr;
           ]
-      | Pexp_assert expr -> Sexp.list [Sexp.atom "Pexp_assert"; expression expr]
       | Pexp_newtype (lbl, expr) ->
         Sexp.list
           [Sexp.atom "Pexp_newtype"; string lbl.Asttypes.txt; expression expr]

compiler/syntax/src/res_comments_table.ml

@@ -1191,13 +1191,6 @@ and walk_expression expr t comments =
       attach t.leading expr2.pexp_loc leading;
       walk_expression expr2 t inside;
       attach t.trailing expr2.pexp_loc trailing
-  | Pexp_assert expr ->
-    if is_block_expr expr then walk_expression expr t comments
-    else
-      let leading, inside, trailing = partition_by_loc comments expr.pexp_loc in
-      attach t.leading expr.pexp_loc leading;
-      walk_expression expr t inside;
-      attach t.trailing expr.pexp_loc trailing
   | Pexp_coerce (expr, (), typexpr) ->
     let leading, inside, trailing = partition_by_loc comments expr.pexp_loc in
     attach t.leading expr.pexp_loc leading;

compiler/syntax/src/res_core.ml

@@ -2374,15 +2374,9 @@ and parse_unary_expr p =
  * If you have `a + b`, `a` and `b` both represent
  * the operands of the binary expression with opeartor `+` *)
 and parse_operand_expr ~context p =
-  let start_pos = p.Parser.start_pos in
   let attrs = ref (parse_attributes p) in
   let expr =
     match p.Parser.token with
-    | Assert ->
-      Parser.next p;
-      let expr = parse_expr p in
-      let loc = mk_loc start_pos p.prev_end_pos in
-      Ast_helper.Exp.assert_ ~loc expr
     | Lident "async"
     (* we need to be careful when we're in a ternary true branch:
        `condition ? ternary-true-branch : false-branch`