improve variadic call using spread syntax (#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