improve variadic call using spread syntax (rescript-lang#7030)

Author: cometkim

CHANGELOG.md

@@ -19,6 +19,7 @@
 #### :nail_care: Polish
 
 - Improve bigint literal comparison. https://github.com/rescript-lang/rescript-compiler/pull/7029
+- Improve output of `@variadic` bindings. https://github.com/rescript-lang/rescript-compiler/pull/7030
 
 # 12.0.0-alpha.3
 

jscomp/core/j.ml

@@ -163,6 +163,7 @@ and expression_desc =
  | Undefined of {is_unit: bool}
  | Null
  | Await of expression
+ | Spread of expression
 
 and for_ident_expression = expression
 (* pure*)

jscomp/core/js_analyzer.ml

@@ -109,6 +109,7 @@ let rec no_side_effect_expression_desc (x : J.expression_desc) =
  (* actually true? *) ->
  false
  | Await _ -> false
+ | Spread _ -> false
 
 and no_side_effect (x : J.expression) =
  no_side_effect_expression_desc x.expression_desc
@@ -212,6 +213,7 @@ let rec eq_expression ({ expression_desc = x0 } : J.expression)
  | Number (Uint _) ->
  false
  | Await _ -> false
+ | Spread _ -> false
 
 and eq_expression_list xs ys = Ext_list.for_all2_no_exn xs ys eq_expression
 

jscomp/core/js_dump.ml

@@ -162,6 +162,7 @@ let rec exp_need_paren ?(arrow=false) (e : J.expression) =
  | Js_not _ | Bool _ | New _ ->
  false
  | Await _ -> false
+ | Spread _ -> false
  | Tagged_template _ -> false
  | Optional_block (e, true) when arrow -> exp_need_paren ~arrow e
  | Optional_block _ -> false
@@ -907,6 +908,10 @@ and expression_desc cxt ~(level : int) f x : cxt =
  P.cond_paren_group f (level > 13) (fun _ ->
  P.string f "await ";
  expression ~level:13 cxt f e)
+ | Spread e ->
+ P.cond_paren_group f (level > 13) (fun _ ->
+ P.string f "...";
+ expression ~level:13 cxt f e)
 
 and property_name_and_value_list cxt f (l : J.property_map) =
  iter_lst cxt f l

jscomp/core/js_exp_make.ml

@@ -1368,3 +1368,9 @@ let neq_null_undefined_boolean ?comment (a : t) (b : t) =
 
 let make_exception (s : string) =
  pure_runtime_call Js_runtime_modules.exceptions Literals.create [ str s ]
+
+let rec variadic_args (args : t list) =
+ match args with
+ | [] -> []
+ | [last] -> [{ last with expression_desc = Spread last }]
+ | arg :: args -> arg :: variadic_args args

jscomp/core/js_exp_make.mli

@@ -364,3 +364,5 @@ val for_sure_js_null_undefined : J.expression -> bool
 val is_null_undefined : ?comment:string -> t -> t
 
 val make_exception : string -> t
+
+val variadic_args : t list -> t list

jscomp/core/js_fold.ml

@@ -177,6 +177,9 @@ class fold =
  | Await _x0 ->
  let _self = _self#expression _x0 in
  _self
+ | Spread _x0 ->
+ let _self = _self#expression _x0 in
+ _self
 
  method for_ident_expression : for_ident_expression -> 'self_type =
  _self#expression

jscomp/core/js_record_fold.ml

@@ -183,6 +183,9 @@ let expression_desc : 'a. ('a, expression_desc) fn =
  | Await _x0 ->
  let st = _self.expression _self st _x0 in
  st
+ | Spread _x0 ->
+ let st = _self.expression _self st _x0 in
+ st
 
 let for_ident_expression : 'a. ('a, for_ident_expression) fn =
  fun _self arg -> _self.expression _self arg

jscomp/core/js_record_iter.ml

@@ -136,6 +136,7 @@ let expression_desc : expression_desc fn =
  | Undefined _ -> ()
  | Null -> ()
  | Await _x0 -> _self.expression _self _x0
+ | Spread _x0 -> _self.expression _self _x0
 
 let for_ident_expression : for_ident_expression fn =
  fun _self arg -> _self.expression _self arg

jscomp/core/js_record_map.ml

@@ -181,6 +181,9 @@ let expression_desc : expression_desc fn =
  | Await _x0 ->
  let _x0 = _self.expression _self _x0 in
  Await _x0
+ | Spread _x0 ->
+ let _x0 = _self.expression _self _x0 in
+ Spread _x0
 
 let for_ident_expression : for_ident_expression fn =
  fun _self arg -> _self.expression _self arg