remove unnecessary parens on function literals

Author: cometkim

jscomp/core/j.ml

@@ -135,6 +135,7 @@ and expression_desc =
       env : Js_fun_env.t;
       return_unit : bool;
       async : bool;
+      iife : bool;
       directive : string option;
     }
   | Str of { delim : delim; txt : string }

jscomp/core/js_dump.ml

@@ -301,7 +301,7 @@ let rec try_optimize_curry cxt f len function_id =
   Curry_gen.pp_optimize_curry f len;
   P.paren_group f 1 (fun _ -> expression ~level:1 cxt f function_id)
 
-and pp_function ~return_unit ~async ~is_method ~need_paren ?directive cxt (f : P.t) ~fn_state
+and pp_function ~return_unit ~async ~is_method ~iife ?directive cxt (f : P.t) ~fn_state
     (l : Ident.t list) (b : J.block) (env : Js_fun_env.t) : cxt =
   match b with
   | [
@@ -426,8 +426,7 @@ and pp_function ~return_unit ~async ~is_method ~need_paren ?directive cxt (f : P
                 P.string f (L.function_ ~async ~arrow);
                 param_body ()
             | No_name _ ->
-                (* see # 1692, add a paren for annoymous function for safety  *)
-                P.cond_paren_group f (need_paren) (fun _ ->
+                P.cond_paren_group f (iife) (fun _ ->
                     P.string f (L.function_ ~async ~arrow);
                     param_body ())
             | Name_non_top x ->
@@ -525,10 +524,9 @@ and expression_desc cxt ~(level : int) f x : cxt =
           let cxt = expression ~level:0 cxt f e1 in
           comma_sp f;
           expression ~level:0 cxt f e2)
-  | Fun { is_method; params; body; env; return_unit; async; directive } ->
+  | Fun { is_method; params; body; env; return_unit; async; iife; directive } ->
       (* TODO: dump for comments *)
-      pp_function ?directive ~is_method ~return_unit ~async
-        ~need_paren:true
+      pp_function ?directive ~is_method ~return_unit ~async ~iife
         ~fn_state:default_fn_exp_state
         cxt f params body env
       (* TODO:
@@ -545,7 +543,11 @@ and expression_desc cxt ~(level : int) f x : cxt =
           P.group f 0 (fun _ ->
               match (info, el) with
               | { arity = Full }, _ | _, [] ->
-                  let cxt = expression ~level:15 cxt f e in
+                  let cxt =
+                    P.cond_paren_group f
+                      (match e.expression_desc with Fun _ -> true | _ -> false)
+                      (fun () -> expression ~level:15 cxt f e )
+                  in
                   P.paren_group f 0 (fun _ ->
                       match el with
                       | [
@@ -559,12 +561,12 @@ and expression_desc cxt ~(level : int) f x : cxt =
                                env;
                                return_unit;
                                async;
+                               iife;
                                directive;
                              };
                        };
                       ] ->
-                          pp_function ?directive ~is_method ~return_unit ~async
-                            ~need_paren:false
+                          pp_function ?directive ~is_method ~return_unit ~async ~iife
                             ~fn_state:(No_name { single_arg = true })
                             cxt f params body env
                       | _ ->
@@ -968,7 +970,7 @@ and variable_declaration top cxt f (variable : J.variable_declaration) : cxt =
           match e.expression_desc with
           | Fun { is_method; params; body; env; return_unit; async; directive } ->
               pp_function ?directive ~is_method ~return_unit ~async
-                ~need_paren:false 
+                ~iife:false 
                 ~fn_state:(if top then Name_top name else Name_non_top name)
                 cxt f params body env
           | _ ->
@@ -1176,10 +1178,10 @@ and statement_desc top cxt f (s : J.statement_desc) : cxt =
       cxt
   | Return e -> (
       match e.expression_desc with
-      | Fun { is_method; params; body; env; return_unit; async; directive } ->
+      | Fun { is_method; params; body; env; return_unit; async; iife; directive } ->
           let cxt =
             pp_function ?directive ~return_unit ~is_method ~async
-              ~need_paren:false
+              ~iife
               ~fn_state:Is_return
               cxt f params body env
           in

jscomp/core/js_exp_make.ml

@@ -207,7 +207,7 @@ let unit : t = { expression_desc = Undefined {is_unit = true}; comment = None }
    [Js_fun_env.empty] is a mutable state ..
 *)
 
-let ocaml_fun ?comment ?immutable_mask ~return_unit ~async ~one_unit_arg ?directive params body : t =
+let ocaml_fun ?comment ?immutable_mask ?(iife = false) ?directive ~return_unit ~async ~one_unit_arg params body : t =
   let params = if one_unit_arg then [] else params in
   let len = List.length params in
   {
@@ -220,12 +220,13 @@ let ocaml_fun ?comment ?immutable_mask ~return_unit ~async ~one_unit_arg ?direct
           env = Js_fun_env.make ?immutable_mask len;
           return_unit;
           async;
+          iife;
           directive;
         };
     comment;
   }
 
-let method_ ?comment ?immutable_mask ~return_unit params body : t =
+let method_ ?comment ?immutable_mask ?(iife = false) ~return_unit params body : t =
   let len = List.length params in
   {
     expression_desc =
@@ -237,6 +238,7 @@ let method_ ?comment ?immutable_mask ~return_unit params body : t =
           env = Js_fun_env.make ?immutable_mask len;
           return_unit;
           async = false;
+          iife;
           directive = None;
         };
     comment;
@@ -1303,6 +1305,7 @@ let of_block ?comment ?e block : t =
             env = Js_fun_env.make 0;
             return_unit;
             async = false;
+            iife = true;
             directive = None;
           };
     }

jscomp/core/js_exp_make.mli

@@ -88,17 +88,19 @@ val str : ?delim: J.delim -> ?comment: string -> string -> t
 val ocaml_fun :
   ?comment:string ->
   ?immutable_mask:bool array ->
+  ?iife:bool ->
+  ?directive:string ->
   return_unit:bool ->
   async:bool ->
   one_unit_arg:bool ->
-  ?directive:string ->
   J.ident list ->
   J.block ->
   t
 
 val method_ :
   ?comment:string ->
   ?immutable_mask:bool array ->
+  ?iife:bool ->
   return_unit:bool ->
   J.ident list ->
   J.block ->