Test: ignore inferred arity in case of %raw.

The inferred arity of raw JS code is actively used with `%ffi`, but it can produce unexpected results with `%raw`:

```
let foo: int => int = %raw(`function add(x, y=5){ return x + y }`)

Console.log(foo(2))
```

Author: cristianoc

CHANGELOG.md

@@ -12,6 +12,9 @@
 
 # 12.0.0-alpha.15 (Unreleased)
 
+#### :bug: Bug fix
+- ignore inferred arity in functions inside `%raw` functions, leaving to `%ffi` the responsibility to check the arity since it gives an error in case of mismatch. https://github.com/rescript-lang/rescript/pull/7542
+
 #### :nail_care: Polish
 
 - Better error message for when trying to await something that is not a promise. https://github.com/rescript-lang/rescript/pull/7561

compiler/core/lam_arity_analysis.ml

@@ -69,8 +69,6 @@ let rec get_arity (meta : Lam_stats.t) (lam : Lam.t) : Lam_arity.t =
     with
     | Submodule subs -> subs.(m) (* TODO: shall we store it as array?*)
     | Single _ -> Lam_arity.na)
-  | Lprim {primitive = Praw_js_code {code_info = Exp (Js_function {arity})}} ->
-    Lam_arity.info [arity] false
   | Lprim {primitive = Praise; _} -> Lam_arity.raise_arity_info
   | Lglobal_module _ (* TODO: fix me never going to happen *) | Lprim _ ->
     Lam_arity.na (* CHECK*)

compiler/core/lam_pass_collect.ml

@@ -64,13 +64,6 @@ let collect_info (meta : Lam_stats.t) (lam : Lam.t) =
     | Lprim {primitive = Psome | Psome_not_nest; args = [v]} ->
       Hash_ident.replace meta.ident_tbl ident (Normal_optional v);
       collect v
-    | Lprim
-        {
-          primitive = Praw_js_code {code_info = Exp (Js_function {arity})};
-          args = _;
-        } ->
-      Hash_ident.replace meta.ident_tbl ident
-        (FunctionId {arity = Lam_arity.info [arity] false; lambda = None})
     | Lprim {primitive = Pnull_to_opt; args = [(Lvar _ as l)]; _} ->
       Hash_ident.replace meta.ident_tbl ident (OptionalBlock (l, Null))
     | Lprim {primitive = Pundefined_to_opt; args = [(Lvar _ as l)]; _} ->

tests/tests/src/raw_arity.mjs

@@ -0,0 +1,11 @@
+// Generated by ReScript, PLEASE EDIT WITH CARE
+
+
+let foo = (function add(x, y=5){ return x + y });
+
+console.log(foo(2));
+
+export {
+  foo,
+}
+/*  Not a pure module */

tests/tests/src/raw_arity.res

@@ -0,0 +1,3 @@
+let foo: int => int = %raw(`function add(x, y=5){ return x + y }`)
+
+Console.log(foo(2))