Begin exposing %raw arity

Only print to stderr for now?

See #6213

Author: cristianoc

jscomp/frontend/ast_exp_handle_external.ml

@@ -72,7 +72,7 @@ let handle_debugger loc (payload : Ast_payload.t) =
     Location.raise_errorf ~loc "%%debugger extension doesn't accept arguments"
 
 let handle_raw ~kind loc payload =
-  let is_function = ref false in
+  let is_function = ref None in
   match Ast_payload.raw_as_string_exp_exn ~kind ~is_function payload with
   | None -> (
     match kind with
@@ -93,9 +93,11 @@ let handle_raw ~kind loc payload =
           ~pval_type:(Typ.arrow Nolabel (Typ.any ()) (Typ.any ()))
           [exp];
       pexp_attributes =
-        (if !is_function then
-         Ast_attributes.internal_expansive :: exp.pexp_attributes
-        else exp.pexp_attributes);
+        (match !is_function with
+        | None -> exp.pexp_attributes
+        | Some arity ->
+          Printf.eprintf "XXX raw arity:%d\n" arity;
+          Ast_attributes.internal_expansive :: exp.pexp_attributes);
     }
 
 let handle_raw_structure loc payload =

jscomp/ml/ast_payload.ml

@@ -138,11 +138,11 @@ let raw_as_string_exp_exn ~(kind : Js_raw_info.raw_kind) ?is_function (x : t) :
            Location.raise_errorf ~loc
              "Syntax error: a valid JS regex literal expected");
         (match is_function with
-        | Some is_function -> (
-          match Classify_function.classify_exp prog with
-          | Js_function {arity = _; _} -> is_function := true
-          | _ -> ())
-        | None -> ());
+          | Some is_function -> (
+            match Classify_function.classify_exp prog with
+            | Js_function {arity; _} -> is_function := Some arity
+            | _ -> ())
+          | None -> ());
         errors
       | Raw_program -> snd (Parser_flow.parse_program false None str));
     Some {e with pexp_desc = Pexp_constant (Pconst_string (str, None))}

jscomp/ml/ast_payload.mli

@@ -47,7 +47,7 @@ val is_single_ident : t -> Longident.t option
 
 val raw_as_string_exp_exn :
   kind:Js_raw_info.raw_kind ->
-  ?is_function:bool ref ->
+  ?is_function:int option ref ->
   t ->
   Parsetree.expression option
 (** Convert %raw into expression *)