From 8f4f487f3f81c8d0d8a1afc316fd6ff86fcbb4b0 Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Thu, 2 Apr 2026 17:42:41 +0200
Subject: [PATCH 1/8] Fix @warning("-102") not working

---
 compiler/core/lam_compile_primitive.ml        |  4 ---
 compiler/ml/builtin_attributes.ml             | 19 ++++++++------
 compiler/ml/builtin_attributes.mli            | 16 ++++++++++--
 compiler/ml/translcore.ml                     | 25 ++++++++++++++-----
 compiler/ml/translmod.ml                      |  7 ++++--
 .../warning102_expr_attribute.res.expected    |  1 +
 ...arning102_structure_attribute.res.expected |  1 +
 .../warning102_value_attribute.res.expected   |  1 +
 .../fixtures/warning102_expr_attribute.res    |  3 +++
 .../warning102_structure_attribute.res        |  3 +++
 .../fixtures/warning102_value_attribute.res   |  1 +
 11 files changed, 60 insertions(+), 21 deletions(-)
 create mode 100644 tests/build_tests/super_errors/expected/warning102_expr_attribute.res.expected
 create mode 100644 tests/build_tests/super_errors/expected/warning102_structure_attribute.res.expected
 create mode 100644 tests/build_tests/super_errors/expected/warning102_value_attribute.res.expected
 create mode 100644 tests/build_tests/super_errors/fixtures/warning102_expr_attribute.res
 create mode 100644 tests/build_tests/super_errors/fixtures/warning102_structure_attribute.res
 create mode 100644 tests/build_tests/super_errors/fixtures/warning102_value_attribute.res

diff --git a/compiler/core/lam_compile_primitive.ml b/compiler/core/lam_compile_primitive.ml
index e7c377e97a7..47aabff81a3 100644
--- a/compiler/core/lam_compile_primitive.ml
+++ b/compiler/core/lam_compile_primitive.ml
@@ -389,23 +389,19 @@ let translate output_prefix loc (cxt : Lam_compile_context.t)
               || E.is_null_undefined_constant e2) ->
       E.neq_null_undefined_boolean e1 e2
     | [e1; e2] ->
-      Location.prerr_warning loc Warnings.Bs_polymorphic_comparison;
       E.runtime_call Primitive_modules.object_
         (Lam_compile_util.runtime_of_comp cmp)
         args
     | _ -> assert false)
   | Pobjorder -> (
-    Location.prerr_warning loc Warnings.Bs_polymorphic_comparison;
     match args with
     | [a; b] -> E.runtime_call Primitive_modules.object_ "compare" args
     | _ -> assert false)
   | Pobjmin -> (
-    Location.prerr_warning loc Warnings.Bs_polymorphic_comparison;
     match args with
     | [a; b] -> E.runtime_call Primitive_modules.object_ "min" args
     | _ -> assert false)
   | Pobjmax -> (
-    Location.prerr_warning loc Warnings.Bs_polymorphic_comparison;
     match args with
     | [a; b] -> E.runtime_call Primitive_modules.object_ "max" args
     | _ -> assert false)
diff --git a/compiler/ml/builtin_attributes.ml b/compiler/ml/builtin_attributes.ml
index a4d073104b4..a1c9aa5514a 100644
--- a/compiler/ml/builtin_attributes.ml
+++ b/compiler/ml/builtin_attributes.ml
@@ -182,17 +182,20 @@ let rec deprecated_of_str = function
     | Some _ as r -> r)
   | _ -> None
 
-let warning_attribute ?(ppwarning = true) =
+let warning_attribute ?(ppwarning = true) ?(report_attribute_errors = true) =
   let process loc txt errflag payload =
     match string_of_payload payload with
     | Some s -> (
       try Warnings.parse_options errflag s
       with Arg.Bad _ ->
-        Location.prerr_warning loc
-          (Warnings.Attribute_payload (txt, "Ill-formed list of warnings")))
+        if report_attribute_errors then
+          Location.prerr_warning loc
+            (Warnings.Attribute_payload (txt, "Ill-formed list of warnings")))
     | None ->
-      Location.prerr_warning loc
-        (Warnings.Attribute_payload (txt, "A single string literal is expected"))
+      if report_attribute_errors then
+        Location.prerr_warning loc
+          (Warnings.Attribute_payload
+             (txt, "A single string literal is expected"))
   in
   function
   | {txt = ("ocaml.warning" | "warning") as txt; loc}, payload ->
@@ -212,10 +215,12 @@ let warning_attribute ?(ppwarning = true) =
     Location.prerr_warning pstr_loc (Warnings.Preprocessor s)
   | _ -> ()
 
-let warning_scope ?ppwarning attrs f =
+let warning_scope ?ppwarning ?report_attribute_errors attrs f =
   let prev = Warnings.backup () in
   try
-    List.iter (warning_attribute ?ppwarning) (List.rev attrs);
+    List.iter
+      (warning_attribute ?ppwarning ?report_attribute_errors)
+      (List.rev attrs);
     let ret = f () in
     Warnings.restore prev;
     ret
diff --git a/compiler/ml/builtin_attributes.mli b/compiler/ml/builtin_attributes.mli
index 63bf7623315..dc2bf958e40 100644
--- a/compiler/ml/builtin_attributes.mli
+++ b/compiler/ml/builtin_attributes.mli
@@ -67,17 +67,29 @@ val check_duplicated_labels :
   (Parsetree.label_declaration list -> string Asttypes.loc option) ref
 val error_of_extension : Parsetree.extension -> Location.error
 
-val warning_attribute : ?ppwarning:bool -> Parsetree.attribute -> unit
+val warning_attribute :
+  ?ppwarning:bool ->
+  ?report_attribute_errors:bool ->
+  Parsetree.attribute ->
+  unit
 (** Apply warning settings from the specified attribute.
       "ocaml.warning"/"ocaml.warnerror" (and variants without the prefix)
       are processed and other attributes are ignored.
 
       Also implement ocaml.ppwarning (unless ~ppwarning:false is
       passed).
+
+      [report_attribute_errors] only controls whether malformed warning
+      attributes emit diagnostics; valid warning settings are still applied
+      regardless.
   *)
 
 val warning_scope :
-  ?ppwarning:bool -> Parsetree.attributes -> (unit -> 'a) -> 'a
+  ?ppwarning:bool ->
+  ?report_attribute_errors:bool ->
+  Parsetree.attributes ->
+  (unit -> 'a) ->
+  'a
 (** Execute a function in a new scope for warning settings.  This
       means that the effect of any call to [warning_attribute] during
       the execution of this function will be discarded after
diff --git a/compiler/ml/translcore.ml b/compiler/ml/translcore.ml
index 078cbf133a0..3d7ba5029c9 100644
--- a/compiler/ml/translcore.ml
+++ b/compiler/ml/translcore.ml
@@ -404,6 +404,15 @@ let primitives_table =
 
 let find_primitive prim_name = Hashtbl.find primitives_table prim_name
 
+let warn_on_polymorphic_comparison loc = function
+  | Pobjcomp _ | Pobjorder | Pobjmin | Pobjmax ->
+    Location.prerr_warning loc Warnings.Bs_polymorphic_comparison
+  | _ -> ()
+
+let emit_primitive_warnings loc primitive =
+  warn_on_polymorphic_comparison loc primitive;
+  primitive
+
 let specialize_comparison
     ({objcomp; intcomp; floatcomp; stringcomp; bigintcomp; boolcomp} :
       specialized) env ty =
@@ -444,8 +453,9 @@ let specialize_primitive p env ty (* ~has_constant_constructor *) =
 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
+    (try specialize_primitive p env ty (* ~has_constant_constructor:false *)
+     with Not_found -> Pccall p)
+    |> emit_primitive_warnings loc
   in
   match prim with
   | Ploc kind -> (
@@ -492,7 +502,7 @@ let transl_primitive_application loc prim env ty args =
     | [arg1] | [arg1; _] -> translate_unified_ops prim env arg1.exp_type
     | _ -> None
   in
-  match unified with
+  (match unified with
   | Some primitive -> primitive
   | None -> (
     try
@@ -524,7 +534,8 @@ let transl_primitive_application loc prim env ty args =
     with Not_found ->
       if String.length prim_name > 0 && prim_name.[0] = '%' then
         raise (Error (loc, Unknown_builtin_primitive prim_name));
-      Pccall prim)
+      Pccall prim))
+  |> emit_primitive_warnings loc
 
 (* To propagate structured constants *)
 
@@ -653,8 +664,10 @@ let extract_directive_for_fn exp =
          else None)
 
 let rec transl_exp e =
-  List.iter (Translattribute.check_attribute e) e.exp_attributes;
-  transl_exp0 e
+  Builtin_attributes.warning_scope ~ppwarning:false
+    ~report_attribute_errors:false e.exp_attributes (fun () ->
+      List.iter (Translattribute.check_attribute e) e.exp_attributes;
+      transl_exp0 e)
 
 and transl_exp0 (e : Typedtree.expression) : Lambda.lambda =
   match e.exp_desc with
diff --git a/compiler/ml/translmod.ml b/compiler/ml/translmod.ml
index 87471ac26bf..729a520e2f7 100644
--- a/compiler/ml/translmod.ml
+++ b/compiler/ml/translmod.ml
@@ -446,8 +446,11 @@ and transl_structure loc fields cc rootpath final_env = function
             transl_module Tcoerce_none None modl,
             body ),
         size )
-    | Tstr_primitive _ | Tstr_type _ | Tstr_modtype _ | Tstr_open _
-    | Tstr_attribute _ ->
+    | Tstr_primitive _ | Tstr_type _ | Tstr_modtype _ | Tstr_open _ ->
+      transl_structure loc fields cc rootpath final_env rem
+    | Tstr_attribute x ->
+      Builtin_attributes.warning_attribute ~ppwarning:false
+        ~report_attribute_errors:false x;
       transl_structure loc fields cc rootpath final_env rem)
 
 (* Update forward declaration in Translcore *)
diff --git a/tests/build_tests/super_errors/expected/warning102_expr_attribute.res.expected b/tests/build_tests/super_errors/expected/warning102_expr_attribute.res.expected
new file mode 100644
index 00000000000..8b137891791
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/warning102_expr_attribute.res.expected
@@ -0,0 +1 @@
+
diff --git a/tests/build_tests/super_errors/expected/warning102_structure_attribute.res.expected b/tests/build_tests/super_errors/expected/warning102_structure_attribute.res.expected
new file mode 100644
index 00000000000..8b137891791
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/warning102_structure_attribute.res.expected
@@ -0,0 +1 @@
+
diff --git a/tests/build_tests/super_errors/expected/warning102_value_attribute.res.expected b/tests/build_tests/super_errors/expected/warning102_value_attribute.res.expected
new file mode 100644
index 00000000000..8b137891791
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/warning102_value_attribute.res.expected
@@ -0,0 +1 @@
+
diff --git a/tests/build_tests/super_errors/fixtures/warning102_expr_attribute.res b/tests/build_tests/super_errors/fixtures/warning102_expr_attribute.res
new file mode 100644
index 00000000000..9bec0b9afbd
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/warning102_expr_attribute.res
@@ -0,0 +1,3 @@
+let x = (a, b) => {
+  @warning("-102") (a->Pair.second > b->Pair.second)
+}
diff --git a/tests/build_tests/super_errors/fixtures/warning102_structure_attribute.res b/tests/build_tests/super_errors/fixtures/warning102_structure_attribute.res
new file mode 100644
index 00000000000..d0ddc537322
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/warning102_structure_attribute.res
@@ -0,0 +1,3 @@
+@@warning("-102")
+
+let x = (a, b) => a->Pair.second > b->Pair.second
diff --git a/tests/build_tests/super_errors/fixtures/warning102_value_attribute.res b/tests/build_tests/super_errors/fixtures/warning102_value_attribute.res
new file mode 100644
index 00000000000..1fb1a49b850
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/warning102_value_attribute.res
@@ -0,0 +1 @@
+let v = @warning("-102") compare

From 165476741a937db43181f5ccd07046dcd671adb4 Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Thu, 2 Apr 2026 20:32:31 +0200
Subject: [PATCH 2/8] fix

---
 compiler/ml/translmod.ml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/compiler/ml/translmod.ml b/compiler/ml/translmod.ml
index 729a520e2f7..595bc912f2b 100644
--- a/compiler/ml/translmod.ml
+++ b/compiler/ml/translmod.ml
@@ -449,9 +449,9 @@ and transl_structure loc fields cc rootpath final_env = function
     | Tstr_primitive _ | Tstr_type _ | Tstr_modtype _ | Tstr_open _ ->
       transl_structure loc fields cc rootpath final_env rem
     | Tstr_attribute x ->
-      Builtin_attributes.warning_attribute ~ppwarning:false
-        ~report_attribute_errors:false x;
-      transl_structure loc fields cc rootpath final_env rem)
+      Builtin_attributes.warning_scope ~ppwarning:false
+        ~report_attribute_errors:false [x] (fun () ->
+          transl_structure loc fields cc rootpath final_env rem))
 
 (* Update forward declaration in Translcore *)
 let _ = Translcore.transl_module := transl_module

From f9e78f2c2a1961170297d35141acc3be87a7f93a Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Fri, 3 Apr 2026 08:37:07 +0200
Subject: [PATCH 3/8] Fix

---
 compiler/ml/translcore.ml                     | 32 ++++++++++++++++---
 .../warning102_nullish_equality.res.expected  |  1 +
 .../fixtures/warning102_nullish_equality.res  |  8 +++++
 3 files changed, 36 insertions(+), 5 deletions(-)
 create mode 100644 tests/build_tests/super_errors/expected/warning102_nullish_equality.res.expected
 create mode 100644 tests/build_tests/super_errors/fixtures/warning102_nullish_equality.res

diff --git a/compiler/ml/translcore.ml b/compiler/ml/translcore.ml
index 3d7ba5029c9..16d742d694b 100644
--- a/compiler/ml/translcore.ml
+++ b/compiler/ml/translcore.ml
@@ -404,13 +404,35 @@ let primitives_table =
 
 let find_primitive prim_name = Hashtbl.find primitives_table prim_name
 
-let warn_on_polymorphic_comparison loc = function
+let is_null_undefined_constant (exp : Typedtree.expression) =
+  match exp.exp_desc with
+  | Texp_ident
+      ( _,
+        _,
+        {
+          val_kind =
+            Val_prim
+              {prim_name = "%null" | "%undefined" | "#null" | "#undefined"; _};
+          _;
+        } ) ->
+    true
+  | _ -> false
+
+let warn_on_polymorphic_comparison loc prim_name args = function
+  (* Preserve the backend's old exemption for == / != against nullish constants,
+     which compile to dedicated null/undefined checks rather than object compare. *)
+  | Pobjcomp (Ceq | Cneq)
+    when prim_name = "%equal_null"
+         || prim_name = "%equal_undefined"
+         || prim_name = "%equal_nullable"
+         || List.exists is_null_undefined_constant args ->
+    ()
   | Pobjcomp _ | Pobjorder | Pobjmin | Pobjmax ->
     Location.prerr_warning loc Warnings.Bs_polymorphic_comparison
   | _ -> ()
 
-let emit_primitive_warnings loc primitive =
-  warn_on_polymorphic_comparison loc primitive;
+let emit_primitive_warnings loc prim_name args primitive =
+  warn_on_polymorphic_comparison loc prim_name args primitive;
   primitive
 
 let specialize_comparison
@@ -455,7 +477,7 @@ let transl_primitive loc p env ty =
   let prim =
     (try specialize_primitive p env ty (* ~has_constant_constructor:false *)
      with Not_found -> Pccall p)
-    |> emit_primitive_warnings loc
+    |> emit_primitive_warnings loc p.prim_name []
   in
   match prim with
   | Ploc kind -> (
@@ -535,7 +557,7 @@ let transl_primitive_application loc prim env ty args =
       if String.length prim_name > 0 && prim_name.[0] = '%' then
         raise (Error (loc, Unknown_builtin_primitive prim_name));
       Pccall prim))
-  |> emit_primitive_warnings loc
+  |> emit_primitive_warnings loc prim_name args
 
 (* To propagate structured constants *)
 
diff --git a/tests/build_tests/super_errors/expected/warning102_nullish_equality.res.expected b/tests/build_tests/super_errors/expected/warning102_nullish_equality.res.expected
new file mode 100644
index 00000000000..8b137891791
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/warning102_nullish_equality.res.expected
@@ -0,0 +1 @@
+
diff --git a/tests/build_tests/super_errors/fixtures/warning102_nullish_equality.res b/tests/build_tests/super_errors/fixtures/warning102_nullish_equality.res
new file mode 100644
index 00000000000..c14079e0403
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/warning102_nullish_equality.res
@@ -0,0 +1,8 @@
+let undefinedEq = undefined == undefined
+let undefinedNeq = undefined != undefined
+
+let nullEq = null == null
+let nullNeq = null != null
+
+let nullableEq = Nullable.undefined == Nullable.make(3)
+let nullableNeq = Nullable.undefined != Nullable.make(3)

From fdc694b0cc0cdf40edab87295b4eba32e8ec4fef Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Fri, 3 Apr 2026 09:11:23 +0200
Subject: [PATCH 4/8] Fix

---
 compiler/ml/typemod.ml                        | 23 ++++++++++++++-----
 .../malformed_warning_attribute.res.expected  | 10 ++++++++
 ...ppwarning_structure_attribute.res.expected |  9 ++++++++
 .../warning102_expr_attribute.res.expected    |  1 -
 .../warning102_nullish_equality.res.expected  |  1 -
 ...rning102_polymorphic_equality.res.expected |  8 +++++++
 ...arning102_structure_attribute.res.expected |  1 -
 .../warning102_value_attribute.res.expected   |  1 -
 .../fixtures/malformed_warning_attribute.res  |  3 +++
 .../ppwarning_structure_attribute.res         |  3 +++
 .../warning102_polymorphic_equality.res       |  1 +
 11 files changed, 51 insertions(+), 10 deletions(-)
 create mode 100644 tests/build_tests/super_errors/expected/malformed_warning_attribute.res.expected
 create mode 100644 tests/build_tests/super_errors/expected/ppwarning_structure_attribute.res.expected
 create mode 100644 tests/build_tests/super_errors/expected/warning102_polymorphic_equality.res.expected
 create mode 100644 tests/build_tests/super_errors/fixtures/malformed_warning_attribute.res
 create mode 100644 tests/build_tests/super_errors/fixtures/ppwarning_structure_attribute.res
 create mode 100644 tests/build_tests/super_errors/fixtures/warning102_polymorphic_equality.res

diff --git a/compiler/ml/typemod.ml b/compiler/ml/typemod.ml
index 0932c62f347..f94898c05fa 100644
--- a/compiler/ml/typemod.ml
+++ b/compiler/ml/typemod.ml
@@ -870,9 +870,10 @@ and transl_signature env sg =
         let trem, rem, final_env = transl_sig newenv srem in
         (mksig (Tsig_include incl) env loc :: trem, sg @ rem, final_env)
       | Psig_attribute x ->
-        Builtin_attributes.warning_attribute x;
-        let trem, rem, final_env = transl_sig env srem in
-        (mksig (Tsig_attribute x) env loc :: trem, rem, final_env)
+        Builtin_attributes.warning_scope ~ppwarning:false
+          ~report_attribute_errors:false [x] (fun () ->
+            let trem, rem, final_env = transl_sig env srem in
+            (mksig (Tsig_attribute x) env loc :: trem, rem, final_env))
       | Psig_extension (ext, _attrs) ->
         raise (Error_forward (Builtin_attributes.error_of_extension ext)))
   in
@@ -1590,14 +1591,24 @@ and type_structure ?(toplevel = false) funct_body anchor env sstr scope =
       (Tstr_include incl, sg, new_env)
     | Pstr_extension (ext, _attrs) ->
       raise (Error_forward (Builtin_attributes.error_of_extension ext))
-    | Pstr_attribute x ->
-      Builtin_attributes.warning_attribute x;
-      (Tstr_attribute x, [], env)
+    | Pstr_attribute x -> (Tstr_attribute x, [], env)
   in
   let rec type_struct env sstr =
     Ctype.init_def (Ident.current_time ());
     match sstr with
     | [] -> ([], [], env)
+    | {pstr_desc = Pstr_attribute x; pstr_loc; _} :: srem ->
+      let previous_saved_types = Cmt_format.get_saved_types () in
+      let str =
+        {str_desc = Tstr_attribute x; str_loc = pstr_loc; str_env = env}
+      in
+      Cmt_format.set_saved_types
+        (Cmt_format.Partial_structure_item str :: previous_saved_types);
+      let str_rem, sig_rem, final_env =
+        Builtin_attributes.warning_scope ~ppwarning:false
+          ~report_attribute_errors:false [x] (fun () -> type_struct env srem)
+      in
+      (str :: str_rem, sig_rem, final_env)
     | pstr :: srem ->
       let previous_saved_types = Cmt_format.get_saved_types () in
       let desc, sg, new_env = type_str_item env srem pstr in
diff --git a/tests/build_tests/super_errors/expected/malformed_warning_attribute.res.expected b/tests/build_tests/super_errors/expected/malformed_warning_attribute.res.expected
new file mode 100644
index 00000000000..428a538da67
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/malformed_warning_attribute.res.expected
@@ -0,0 +1,10 @@
+
+  Warning number 47
+  /.../fixtures/malformed_warning_attribute.res:1:1-9
+
+  1 │ @@warning(123)
+  2 │ 
+  3 │ let x = 1
+
+  illegal payload for attribute 'warning'.
+A single string literal is expected
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/expected/ppwarning_structure_attribute.res.expected b/tests/build_tests/super_errors/expected/ppwarning_structure_attribute.res.expected
new file mode 100644
index 00000000000..3ff8ada406b
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/ppwarning_structure_attribute.res.expected
@@ -0,0 +1,9 @@
+
+  Warning number 22
+  /.../fixtures/ppwarning_structure_attribute.res:1:13-19
+
+  1 │ @@ppwarning("hello")
+  2 │ 
+  3 │ let x = 1
+
+  hello
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/expected/warning102_expr_attribute.res.expected b/tests/build_tests/super_errors/expected/warning102_expr_attribute.res.expected
index 8b137891791..e69de29bb2d 100644
--- a/tests/build_tests/super_errors/expected/warning102_expr_attribute.res.expected
+++ b/tests/build_tests/super_errors/expected/warning102_expr_attribute.res.expected
@@ -1 +0,0 @@
-
diff --git a/tests/build_tests/super_errors/expected/warning102_nullish_equality.res.expected b/tests/build_tests/super_errors/expected/warning102_nullish_equality.res.expected
index 8b137891791..e69de29bb2d 100644
--- a/tests/build_tests/super_errors/expected/warning102_nullish_equality.res.expected
+++ b/tests/build_tests/super_errors/expected/warning102_nullish_equality.res.expected
@@ -1 +0,0 @@
-
diff --git a/tests/build_tests/super_errors/expected/warning102_polymorphic_equality.res.expected b/tests/build_tests/super_errors/expected/warning102_polymorphic_equality.res.expected
new file mode 100644
index 00000000000..98c7b2fb391
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/warning102_polymorphic_equality.res.expected
@@ -0,0 +1,8 @@
+
+  Warning number 102
+  /.../fixtures/warning102_polymorphic_equality.res:1:19-24
+
+  1 │ let f = (a, b) => a == b
+  2 │ 
+
+  Polymorphic comparison introduced (maybe unsafe)
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/expected/warning102_structure_attribute.res.expected b/tests/build_tests/super_errors/expected/warning102_structure_attribute.res.expected
index 8b137891791..e69de29bb2d 100644
--- a/tests/build_tests/super_errors/expected/warning102_structure_attribute.res.expected
+++ b/tests/build_tests/super_errors/expected/warning102_structure_attribute.res.expected
@@ -1 +0,0 @@
-
diff --git a/tests/build_tests/super_errors/expected/warning102_value_attribute.res.expected b/tests/build_tests/super_errors/expected/warning102_value_attribute.res.expected
index 8b137891791..e69de29bb2d 100644
--- a/tests/build_tests/super_errors/expected/warning102_value_attribute.res.expected
+++ b/tests/build_tests/super_errors/expected/warning102_value_attribute.res.expected
@@ -1 +0,0 @@
-
diff --git a/tests/build_tests/super_errors/fixtures/malformed_warning_attribute.res b/tests/build_tests/super_errors/fixtures/malformed_warning_attribute.res
new file mode 100644
index 00000000000..3951cf99fc1
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/malformed_warning_attribute.res
@@ -0,0 +1,3 @@
+@@warning(123)
+
+let x = 1
diff --git a/tests/build_tests/super_errors/fixtures/ppwarning_structure_attribute.res b/tests/build_tests/super_errors/fixtures/ppwarning_structure_attribute.res
new file mode 100644
index 00000000000..7d21223a7a9
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/ppwarning_structure_attribute.res
@@ -0,0 +1,3 @@
+@@ppwarning("hello")
+
+let x = 1
diff --git a/tests/build_tests/super_errors/fixtures/warning102_polymorphic_equality.res b/tests/build_tests/super_errors/fixtures/warning102_polymorphic_equality.res
new file mode 100644
index 00000000000..16c9337f925
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/warning102_polymorphic_equality.res
@@ -0,0 +1 @@
+let f = (a, b) => a == b

From b73831974dbb5445a09a7630bcc8954e8be88fcd Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Fri, 3 Apr 2026 09:21:36 +0200
Subject: [PATCH 5/8] .resi tests

---
 compiler/ml/typemod.ml                                 |  5 +++++
 .../expected/malformed_warning_attribute.resi.expected | 10 ++++++++++
 .../ppwarning_signature_attribute.resi.expected        |  9 +++++++++
 .../fixtures/malformed_warning_attribute.resi          |  3 +++
 .../fixtures/ppwarning_signature_attribute.resi        |  3 +++
 tests/build_tests/super_errors/input.js                |  2 +-
 6 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 tests/build_tests/super_errors/expected/malformed_warning_attribute.resi.expected
 create mode 100644 tests/build_tests/super_errors/expected/ppwarning_signature_attribute.resi.expected
 create mode 100644 tests/build_tests/super_errors/fixtures/malformed_warning_attribute.resi
 create mode 100644 tests/build_tests/super_errors/fixtures/ppwarning_signature_attribute.resi

diff --git a/compiler/ml/typemod.ml b/compiler/ml/typemod.ml
index f94898c05fa..db0524adc39 100644
--- a/compiler/ml/typemod.ml
+++ b/compiler/ml/typemod.ml
@@ -870,6 +870,9 @@ and transl_signature env sg =
         let trem, rem, final_env = transl_sig newenv srem in
         (mksig (Tsig_include incl) env loc :: trem, sg @ rem, final_env)
       | Psig_attribute x ->
+        (* The frontend pre-pass already emitted @@ppwarning and malformed
+           @@warning diagnostics; only thread the warning state here so the
+           remaining signature items see the right settings. *)
         Builtin_attributes.warning_scope ~ppwarning:false
           ~report_attribute_errors:false [x] (fun () ->
             let trem, rem, final_env = transl_sig env srem in
@@ -1605,6 +1608,8 @@ and type_structure ?(toplevel = false) funct_body anchor env sstr scope =
       Cmt_format.set_saved_types
         (Cmt_format.Partial_structure_item str :: previous_saved_types);
       let str_rem, sig_rem, final_env =
+        (* Floating warning-attribute diagnostics are handled in the frontend
+           pass; this scope only applies their effect to following items. *)
         Builtin_attributes.warning_scope ~ppwarning:false
           ~report_attribute_errors:false [x] (fun () -> type_struct env srem)
       in
diff --git a/tests/build_tests/super_errors/expected/malformed_warning_attribute.resi.expected b/tests/build_tests/super_errors/expected/malformed_warning_attribute.resi.expected
new file mode 100644
index 00000000000..489b10a0603
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/malformed_warning_attribute.resi.expected
@@ -0,0 +1,10 @@
+
+  Warning number 47
+  /.../fixtures/malformed_warning_attribute.resi:1:1-9
+
+  1 │ @@warning(123)
+  2 │ 
+  3 │ let x: int
+
+  illegal payload for attribute 'warning'.
+A single string literal is expected
diff --git a/tests/build_tests/super_errors/expected/ppwarning_signature_attribute.resi.expected b/tests/build_tests/super_errors/expected/ppwarning_signature_attribute.resi.expected
new file mode 100644
index 00000000000..ca0612eab85
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/ppwarning_signature_attribute.resi.expected
@@ -0,0 +1,9 @@
+
+  Warning number 22
+  /.../fixtures/ppwarning_signature_attribute.resi:1:13-19
+
+  1 │ @@ppwarning("hello")
+  2 │ 
+  3 │ let x: int
+
+  hello
diff --git a/tests/build_tests/super_errors/fixtures/malformed_warning_attribute.resi b/tests/build_tests/super_errors/fixtures/malformed_warning_attribute.resi
new file mode 100644
index 00000000000..cd7eec4e6c1
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/malformed_warning_attribute.resi
@@ -0,0 +1,3 @@
+@@warning(123)
+
+let x: int
diff --git a/tests/build_tests/super_errors/fixtures/ppwarning_signature_attribute.resi b/tests/build_tests/super_errors/fixtures/ppwarning_signature_attribute.resi
new file mode 100644
index 00000000000..95597ae052d
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/ppwarning_signature_attribute.resi
@@ -0,0 +1,3 @@
+@@ppwarning("hello")
+
+let x: int
diff --git a/tests/build_tests/super_errors/input.js b/tests/build_tests/super_errors/input.js
index 3ea9e08c68d..822428371ca 100644
--- a/tests/build_tests/super_errors/input.js
+++ b/tests/build_tests/super_errors/input.js
@@ -11,7 +11,7 @@ const { bsc } = setup(import.meta.dirname);
 const expectedDir = path.join(import.meta.dirname, "expected");
 
 const fixtures = readdirSync(path.join(import.meta.dirname, "fixtures")).filter(
-  fileName => path.extname(fileName) === ".res",
+  fileName => [".res", ".resi"].includes(path.extname(fileName)),
 );
 
 const prefix = ["-w", "+A", "-bs-jsx", "4"];

From a937c43f73f7dfba353086ecd96490094180a16c Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Fri, 3 Apr 2026 09:52:08 +0200
Subject: [PATCH 6/8] Simplify

---
 compiler/ml/builtin_attributes.ml  |  3 +++
 compiler/ml/builtin_attributes.mli |  8 ++++++++
 compiler/ml/translcore.ml          |  4 ++--
 compiler/ml/translmod.ml           |  5 ++---
 compiler/ml/typemod.ml             | 13 ++++---------
 5 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/compiler/ml/builtin_attributes.ml b/compiler/ml/builtin_attributes.ml
index a1c9aa5514a..c3e3b93411d 100644
--- a/compiler/ml/builtin_attributes.ml
+++ b/compiler/ml/builtin_attributes.ml
@@ -228,6 +228,9 @@ let warning_scope ?ppwarning ?report_attribute_errors attrs f =
     Warnings.restore prev;
     raise exn
 
+let warning_scope_without_attribute_diagnostics attrs f =
+  warning_scope ~ppwarning:false ~report_attribute_errors:false attrs f
+
 let warn_on_literal_pattern =
   List.exists (function
     | {txt = "ocaml.warn_on_literal_pattern" | "warn_on_literal_pattern"; _}, _
diff --git a/compiler/ml/builtin_attributes.mli b/compiler/ml/builtin_attributes.mli
index dc2bf958e40..aa6282749a5 100644
--- a/compiler/ml/builtin_attributes.mli
+++ b/compiler/ml/builtin_attributes.mli
@@ -100,6 +100,14 @@ val warning_scope :
       is executed.
   *)
 
+val warning_scope_without_attribute_diagnostics :
+  Parsetree.attributes -> (unit -> 'a) -> 'a
+(** Like [warning_scope], but suppresses diagnostics that have already been
+      emitted during the frontend warning-attribute pass (such as
+      [@@ppwarning] and malformed warning payloads). The warning settings are
+      still applied to the nested computation.
+  *)
+
 val warn_on_literal_pattern : Parsetree.attributes -> bool
 val explicit_arity : Parsetree.attributes -> bool
 
diff --git a/compiler/ml/translcore.ml b/compiler/ml/translcore.ml
index 16d742d694b..826e3773641 100644
--- a/compiler/ml/translcore.ml
+++ b/compiler/ml/translcore.ml
@@ -686,8 +686,8 @@ let extract_directive_for_fn exp =
          else None)
 
 let rec transl_exp e =
-  Builtin_attributes.warning_scope ~ppwarning:false
-    ~report_attribute_errors:false e.exp_attributes (fun () ->
+  Builtin_attributes.warning_scope_without_attribute_diagnostics
+    e.exp_attributes (fun () ->
       List.iter (Translattribute.check_attribute e) e.exp_attributes;
       transl_exp0 e)
 
diff --git a/compiler/ml/translmod.ml b/compiler/ml/translmod.ml
index 595bc912f2b..dd1bc533a1c 100644
--- a/compiler/ml/translmod.ml
+++ b/compiler/ml/translmod.ml
@@ -449,9 +449,8 @@ and transl_structure loc fields cc rootpath final_env = function
     | Tstr_primitive _ | Tstr_type _ | Tstr_modtype _ | Tstr_open _ ->
       transl_structure loc fields cc rootpath final_env rem
     | Tstr_attribute x ->
-      Builtin_attributes.warning_scope ~ppwarning:false
-        ~report_attribute_errors:false [x] (fun () ->
-          transl_structure loc fields cc rootpath final_env rem))
+      Builtin_attributes.warning_scope_without_attribute_diagnostics [x]
+        (fun () -> transl_structure loc fields cc rootpath final_env rem))
 
 (* Update forward declaration in Translcore *)
 let _ = Translcore.transl_module := transl_module
diff --git a/compiler/ml/typemod.ml b/compiler/ml/typemod.ml
index db0524adc39..c88c7201637 100644
--- a/compiler/ml/typemod.ml
+++ b/compiler/ml/typemod.ml
@@ -870,11 +870,8 @@ and transl_signature env sg =
         let trem, rem, final_env = transl_sig newenv srem in
         (mksig (Tsig_include incl) env loc :: trem, sg @ rem, final_env)
       | Psig_attribute x ->
-        (* The frontend pre-pass already emitted @@ppwarning and malformed
-           @@warning diagnostics; only thread the warning state here so the
-           remaining signature items see the right settings. *)
-        Builtin_attributes.warning_scope ~ppwarning:false
-          ~report_attribute_errors:false [x] (fun () ->
+        Builtin_attributes.warning_scope_without_attribute_diagnostics [x]
+          (fun () ->
             let trem, rem, final_env = transl_sig env srem in
             (mksig (Tsig_attribute x) env loc :: trem, rem, final_env))
       | Psig_extension (ext, _attrs) ->
@@ -1608,10 +1605,8 @@ and type_structure ?(toplevel = false) funct_body anchor env sstr scope =
       Cmt_format.set_saved_types
         (Cmt_format.Partial_structure_item str :: previous_saved_types);
       let str_rem, sig_rem, final_env =
-        (* Floating warning-attribute diagnostics are handled in the frontend
-           pass; this scope only applies their effect to following items. *)
-        Builtin_attributes.warning_scope ~ppwarning:false
-          ~report_attribute_errors:false [x] (fun () -> type_struct env srem)
+        Builtin_attributes.warning_scope_without_attribute_diagnostics [x]
+          (fun () -> type_struct env srem)
       in
       (str :: str_rem, sig_rem, final_env)
     | pstr :: srem ->

From ee289bc63d877820df080313c2a811a53bc48f82 Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Fri, 3 Apr 2026 10:29:28 +0200
Subject: [PATCH 7/8] Update comment

---
 compiler/ml/translcore.ml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/compiler/ml/translcore.ml b/compiler/ml/translcore.ml
index 826e3773641..42ed7a23a9f 100644
--- a/compiler/ml/translcore.ml
+++ b/compiler/ml/translcore.ml
@@ -419,8 +419,8 @@ let is_null_undefined_constant (exp : Typedtree.expression) =
   | _ -> false
 
 let warn_on_polymorphic_comparison loc prim_name args = function
-  (* Preserve the backend's old exemption for == / != against nullish constants,
-     which compile to dedicated null/undefined checks rather than object compare. *)
+  (* Skip warning 102 for `==` / `!=` when one side is a nullish constant:
+     those cases lower to dedicated null/undefined checks, not object comparison. *)
   | Pobjcomp (Ceq | Cneq)
     when prim_name = "%equal_null"
          || prim_name = "%equal_undefined"

From c4f4a87c2d818c33def297610e4b34f5ab01f48b Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Fri, 3 Apr 2026 13:53:41 +0200
Subject: [PATCH 8/8] Fix

---
 compiler/frontend/bs_ast_invariant.ml         | 45 ++++++++++---------
 compiler/frontend/bs_ast_invariant.mli        |  4 +-
 compiler/frontend/ppx_entry.ml                |  4 +-
 .../malformed_warning_attribute.resi.expected |  2 +-
 ..._warning_signature_attribute.resi.expected | 12 +++++
 ...d_warning_structure_attribute.res.expected | 12 +++++
 ...pwarning_signature_attribute.resi.expected | 11 +++++
 ...ppwarning_structure_attribute.res.expected | 11 +++++
 ..._warning_signature_attribute.resi.expected | 10 +++++
 ...d_warning_structure_attribute.res.expected | 10 +++++
 ...pwarning_signature_attribute.resi.expected |  9 ++++
 ...ppwarning_structure_attribute.res.expected |  9 ++++
 ...pwarning_signature_attribute.resi.expected |  2 +-
 ...malformed_warning_signature_attribute.resi |  4 ++
 ..._malformed_warning_structure_attribute.res |  4 ++
 .../nested_ppwarning_signature_attribute.resi |  4 ++
 .../nested_ppwarning_structure_attribute.res  |  4 ++
 ...malformed_warning_signature_attribute.resi |  2 +
 ..._malformed_warning_structure_attribute.res |  2 +
 ...leading_ppwarning_signature_attribute.resi |  2 +
 ...nleading_ppwarning_structure_attribute.res |  2 +
 21 files changed, 137 insertions(+), 28 deletions(-)
 create mode 100644 tests/build_tests/super_errors/expected/nested_malformed_warning_signature_attribute.resi.expected
 create mode 100644 tests/build_tests/super_errors/expected/nested_malformed_warning_structure_attribute.res.expected
 create mode 100644 tests/build_tests/super_errors/expected/nested_ppwarning_signature_attribute.resi.expected
 create mode 100644 tests/build_tests/super_errors/expected/nested_ppwarning_structure_attribute.res.expected
 create mode 100644 tests/build_tests/super_errors/expected/nonleading_malformed_warning_signature_attribute.resi.expected
 create mode 100644 tests/build_tests/super_errors/expected/nonleading_malformed_warning_structure_attribute.res.expected
 create mode 100644 tests/build_tests/super_errors/expected/nonleading_ppwarning_signature_attribute.resi.expected
 create mode 100644 tests/build_tests/super_errors/expected/nonleading_ppwarning_structure_attribute.res.expected
 create mode 100644 tests/build_tests/super_errors/fixtures/nested_malformed_warning_signature_attribute.resi
 create mode 100644 tests/build_tests/super_errors/fixtures/nested_malformed_warning_structure_attribute.res
 create mode 100644 tests/build_tests/super_errors/fixtures/nested_ppwarning_signature_attribute.resi
 create mode 100644 tests/build_tests/super_errors/fixtures/nested_ppwarning_structure_attribute.res
 create mode 100644 tests/build_tests/super_errors/fixtures/nonleading_malformed_warning_signature_attribute.resi
 create mode 100644 tests/build_tests/super_errors/fixtures/nonleading_malformed_warning_structure_attribute.res
 create mode 100644 tests/build_tests/super_errors/fixtures/nonleading_ppwarning_signature_attribute.resi
 create mode 100644 tests/build_tests/super_errors/fixtures/nonleading_ppwarning_structure_attribute.res

diff --git a/compiler/frontend/bs_ast_invariant.ml b/compiler/frontend/bs_ast_invariant.ml
index cbe5a4432ee..48ccb422a16 100644
--- a/compiler/frontend/bs_ast_invariant.ml
+++ b/compiler/frontend/bs_ast_invariant.ml
@@ -50,6 +50,21 @@ type iterator = Ast_iterator.iterator
 
 let super = Ast_iterator.default_iterator
 
+let warning_attribute_iterator =
+  let structure_item self (structure_item : Parsetree.structure_item) =
+    (match structure_item.pstr_desc with
+    | Pstr_attribute attr -> Builtin_attributes.warning_attribute attr
+    | _ -> ());
+    super.structure_item self structure_item
+  in
+  let signature_item self (signature_item : Parsetree.signature_item) =
+    (match signature_item.psig_desc with
+    | Psig_attribute attr -> Builtin_attributes.warning_attribute attr
+    | _ -> ());
+    super.signature_item self signature_item
+  in
+  {super with structure_item; signature_item}
+
 let check_constant loc (const : Parsetree.constant) =
   match const with
   | Pconst_string (_, Some s) ->
@@ -148,28 +163,14 @@ let emit_external_warnings : iterator =
         | _ -> super.pat self pat);
   }
 
-let rec iter_warnings_on_stru (stru : Parsetree.structure) =
-  match stru with
-  | [] -> ()
-  | head :: rest -> (
-    match head.pstr_desc with
-    | Pstr_attribute attr ->
-      Builtin_attributes.warning_attribute attr;
-      iter_warnings_on_stru rest
-    | _ -> ())
+let iter_warnings_on_structure (structure : Parsetree.structure) =
+  warning_attribute_iterator.structure warning_attribute_iterator structure
 
-let rec iter_warnings_on_sigi (stru : Parsetree.signature) =
-  match stru with
-  | [] -> ()
-  | head :: rest -> (
-    match head.psig_desc with
-    | Psig_attribute attr ->
-      Builtin_attributes.warning_attribute attr;
-      iter_warnings_on_sigi rest
-    | _ -> ())
+let iter_warnings_on_signature (signature : Parsetree.signature) =
+  warning_attribute_iterator.signature warning_attribute_iterator signature
 
-let emit_external_warnings_on_structure (stru : Parsetree.structure) =
-  emit_external_warnings.structure emit_external_warnings stru
+let emit_external_warnings_on_structure (structure : Parsetree.structure) =
+  emit_external_warnings.structure emit_external_warnings structure
 
-let emit_external_warnings_on_signature (sigi : Parsetree.signature) =
-  emit_external_warnings.signature emit_external_warnings sigi
+let emit_external_warnings_on_signature (signature : Parsetree.signature) =
+  emit_external_warnings.signature emit_external_warnings signature
diff --git a/compiler/frontend/bs_ast_invariant.mli b/compiler/frontend/bs_ast_invariant.mli
index b3b580ebfa5..667d6b863d2 100644
--- a/compiler/frontend/bs_ast_invariant.mli
+++ b/compiler/frontend/bs_ast_invariant.mli
@@ -30,9 +30,9 @@ type iterator = Ast_iterator.iterator
 val warn_discarded_unused_attributes : Parsetree.attributes -> unit
 (** Ast invariant checking for detecting errors *)
 
-val iter_warnings_on_stru : Parsetree.structure -> unit
+val iter_warnings_on_structure : Parsetree.structure -> unit
 
-val iter_warnings_on_sigi : Parsetree.signature -> unit
+val iter_warnings_on_signature : Parsetree.signature -> unit
 
 val emit_external_warnings_on_structure : Parsetree.structure -> unit
 
diff --git a/compiler/frontend/ppx_entry.ml b/compiler/frontend/ppx_entry.ml
index e86949064f7..4afeaf2d442 100644
--- a/compiler/frontend/ppx_entry.ml
+++ b/compiler/frontend/ppx_entry.ml
@@ -25,7 +25,7 @@
 let unsafe_mapper = Bs_builtin_ppx.mapper
 
 let rewrite_signature (ast : Parsetree.signature) : Parsetree.signature =
-  Bs_ast_invariant.iter_warnings_on_sigi ast;
+  Bs_ast_invariant.iter_warnings_on_signature ast;
   Ast_config.process_sig ast;
   let ast =
     match !Js_config.jsx_version with
@@ -44,7 +44,7 @@ let rewrite_signature (ast : Parsetree.signature) : Parsetree.signature =
     result
 
 let rewrite_implementation (ast : Parsetree.structure) : Parsetree.structure =
-  Bs_ast_invariant.iter_warnings_on_stru ast;
+  Bs_ast_invariant.iter_warnings_on_structure ast;
   Ast_config.process_str ast;
   let ast =
     match !Js_config.jsx_version with
diff --git a/tests/build_tests/super_errors/expected/malformed_warning_attribute.resi.expected b/tests/build_tests/super_errors/expected/malformed_warning_attribute.resi.expected
index 489b10a0603..d64681c8120 100644
--- a/tests/build_tests/super_errors/expected/malformed_warning_attribute.resi.expected
+++ b/tests/build_tests/super_errors/expected/malformed_warning_attribute.resi.expected
@@ -7,4 +7,4 @@
   3 │ let x: int
 
   illegal payload for attribute 'warning'.
-A single string literal is expected
+A single string literal is expected
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/expected/nested_malformed_warning_signature_attribute.resi.expected b/tests/build_tests/super_errors/expected/nested_malformed_warning_signature_attribute.resi.expected
new file mode 100644
index 00000000000..721f234b4be
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/nested_malformed_warning_signature_attribute.resi.expected
@@ -0,0 +1,12 @@
+
+  Warning number 47
+  /.../fixtures/nested_malformed_warning_signature_attribute.resi:3:3-11
+
+  1 │ module M: {
+  2 │   let y: int
+  3 │   @@warning(123)
+  4 │ }
+  5 │ 
+
+  illegal payload for attribute 'warning'.
+A single string literal is expected
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/expected/nested_malformed_warning_structure_attribute.res.expected b/tests/build_tests/super_errors/expected/nested_malformed_warning_structure_attribute.res.expected
new file mode 100644
index 00000000000..0d60d9eb9bd
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/nested_malformed_warning_structure_attribute.res.expected
@@ -0,0 +1,12 @@
+
+  Warning number 47
+  /.../fixtures/nested_malformed_warning_structure_attribute.res:3:3-11
+
+  1 │ module M = {
+  2 │   let y = 1
+  3 │   @@warning(123)
+  4 │ }
+  5 │ 
+
+  illegal payload for attribute 'warning'.
+A single string literal is expected
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/expected/nested_ppwarning_signature_attribute.resi.expected b/tests/build_tests/super_errors/expected/nested_ppwarning_signature_attribute.resi.expected
new file mode 100644
index 00000000000..dc8bd5968d4
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/nested_ppwarning_signature_attribute.resi.expected
@@ -0,0 +1,11 @@
+
+  Warning number 22
+  /.../fixtures/nested_ppwarning_signature_attribute.resi:3:15-21
+
+  1 │ module M: {
+  2 │   let y: int
+  3 │   @@ppwarning("hello")
+  4 │ }
+  5 │ 
+
+  hello
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/expected/nested_ppwarning_structure_attribute.res.expected b/tests/build_tests/super_errors/expected/nested_ppwarning_structure_attribute.res.expected
new file mode 100644
index 00000000000..67a8db2b4aa
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/nested_ppwarning_structure_attribute.res.expected
@@ -0,0 +1,11 @@
+
+  Warning number 22
+  /.../fixtures/nested_ppwarning_structure_attribute.res:3:15-21
+
+  1 │ module M = {
+  2 │   let y = 1
+  3 │   @@ppwarning("hello")
+  4 │ }
+  5 │ 
+
+  hello
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/expected/nonleading_malformed_warning_signature_attribute.resi.expected b/tests/build_tests/super_errors/expected/nonleading_malformed_warning_signature_attribute.resi.expected
new file mode 100644
index 00000000000..a9b354f6d60
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/nonleading_malformed_warning_signature_attribute.resi.expected
@@ -0,0 +1,10 @@
+
+  Warning number 47
+  /.../fixtures/nonleading_malformed_warning_signature_attribute.resi:2:1-9
+
+  1 │ let y: int
+  2 │ @@warning(123)
+  3 │ 
+
+  illegal payload for attribute 'warning'.
+A single string literal is expected
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/expected/nonleading_malformed_warning_structure_attribute.res.expected b/tests/build_tests/super_errors/expected/nonleading_malformed_warning_structure_attribute.res.expected
new file mode 100644
index 00000000000..78ab2f89bc1
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/nonleading_malformed_warning_structure_attribute.res.expected
@@ -0,0 +1,10 @@
+
+  Warning number 47
+  /.../fixtures/nonleading_malformed_warning_structure_attribute.res:2:1-9
+
+  1 │ let y = 1
+  2 │ @@warning(123)
+  3 │ 
+
+  illegal payload for attribute 'warning'.
+A single string literal is expected
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/expected/nonleading_ppwarning_signature_attribute.resi.expected b/tests/build_tests/super_errors/expected/nonleading_ppwarning_signature_attribute.resi.expected
new file mode 100644
index 00000000000..1a29e2be231
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/nonleading_ppwarning_signature_attribute.resi.expected
@@ -0,0 +1,9 @@
+
+  Warning number 22
+  /.../fixtures/nonleading_ppwarning_signature_attribute.resi:2:13-19
+
+  1 │ let y: int
+  2 │ @@ppwarning("hello")
+  3 │ 
+
+  hello
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/expected/nonleading_ppwarning_structure_attribute.res.expected b/tests/build_tests/super_errors/expected/nonleading_ppwarning_structure_attribute.res.expected
new file mode 100644
index 00000000000..0c5b2df957f
--- /dev/null
+++ b/tests/build_tests/super_errors/expected/nonleading_ppwarning_structure_attribute.res.expected
@@ -0,0 +1,9 @@
+
+  Warning number 22
+  /.../fixtures/nonleading_ppwarning_structure_attribute.res:2:13-19
+
+  1 │ let y = 1
+  2 │ @@ppwarning("hello")
+  3 │ 
+
+  hello
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/expected/ppwarning_signature_attribute.resi.expected b/tests/build_tests/super_errors/expected/ppwarning_signature_attribute.resi.expected
index ca0612eab85..a7a9a73084f 100644
--- a/tests/build_tests/super_errors/expected/ppwarning_signature_attribute.resi.expected
+++ b/tests/build_tests/super_errors/expected/ppwarning_signature_attribute.resi.expected
@@ -6,4 +6,4 @@
   2 │ 
   3 │ let x: int
 
-  hello
+  hello
\ No newline at end of file
diff --git a/tests/build_tests/super_errors/fixtures/nested_malformed_warning_signature_attribute.resi b/tests/build_tests/super_errors/fixtures/nested_malformed_warning_signature_attribute.resi
new file mode 100644
index 00000000000..f5eae9c9198
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/nested_malformed_warning_signature_attribute.resi
@@ -0,0 +1,4 @@
+module M: {
+  let y: int
+  @@warning(123)
+}
diff --git a/tests/build_tests/super_errors/fixtures/nested_malformed_warning_structure_attribute.res b/tests/build_tests/super_errors/fixtures/nested_malformed_warning_structure_attribute.res
new file mode 100644
index 00000000000..a6fe5be712a
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/nested_malformed_warning_structure_attribute.res
@@ -0,0 +1,4 @@
+module M = {
+  let y = 1
+  @@warning(123)
+}
diff --git a/tests/build_tests/super_errors/fixtures/nested_ppwarning_signature_attribute.resi b/tests/build_tests/super_errors/fixtures/nested_ppwarning_signature_attribute.resi
new file mode 100644
index 00000000000..b2b9041016a
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/nested_ppwarning_signature_attribute.resi
@@ -0,0 +1,4 @@
+module M: {
+  let y: int
+  @@ppwarning("hello")
+}
diff --git a/tests/build_tests/super_errors/fixtures/nested_ppwarning_structure_attribute.res b/tests/build_tests/super_errors/fixtures/nested_ppwarning_structure_attribute.res
new file mode 100644
index 00000000000..fb87c43da8c
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/nested_ppwarning_structure_attribute.res
@@ -0,0 +1,4 @@
+module M = {
+  let y = 1
+  @@ppwarning("hello")
+}
diff --git a/tests/build_tests/super_errors/fixtures/nonleading_malformed_warning_signature_attribute.resi b/tests/build_tests/super_errors/fixtures/nonleading_malformed_warning_signature_attribute.resi
new file mode 100644
index 00000000000..65cc613f38a
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/nonleading_malformed_warning_signature_attribute.resi
@@ -0,0 +1,2 @@
+let y: int
+@@warning(123)
diff --git a/tests/build_tests/super_errors/fixtures/nonleading_malformed_warning_structure_attribute.res b/tests/build_tests/super_errors/fixtures/nonleading_malformed_warning_structure_attribute.res
new file mode 100644
index 00000000000..fa0d1033a8e
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/nonleading_malformed_warning_structure_attribute.res
@@ -0,0 +1,2 @@
+let y = 1
+@@warning(123)
diff --git a/tests/build_tests/super_errors/fixtures/nonleading_ppwarning_signature_attribute.resi b/tests/build_tests/super_errors/fixtures/nonleading_ppwarning_signature_attribute.resi
new file mode 100644
index 00000000000..b110d72c831
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/nonleading_ppwarning_signature_attribute.resi
@@ -0,0 +1,2 @@
+let y: int
+@@ppwarning("hello")
diff --git a/tests/build_tests/super_errors/fixtures/nonleading_ppwarning_structure_attribute.res b/tests/build_tests/super_errors/fixtures/nonleading_ppwarning_structure_attribute.res
new file mode 100644
index 00000000000..35c88da5634
--- /dev/null
+++ b/tests/build_tests/super_errors/fixtures/nonleading_ppwarning_structure_attribute.res
@@ -0,0 +1,2 @@
+let y = 1
+@@ppwarning("hello")