add a test case for labeled const

TODO: labeled const does not really make sense, we should disable it in the syntax level
```
external on_exit_slice3 :
    int
    -> h:(_ [@bs.as 3])
    -> (_ [@bs.as "xxx"])
    -> int array
    -> unit
    =
    "xx"    [@@bs.send.pipe: t] [@@bs.splice]
```

Author: bobzhang

jscomp/main/builtin_cmi_datasets.ml

@@ -2,6 +2,11 @@
 
 var Curry = require("../../lib/js/curry.js");
 
+function test(g) {
+  g.xx(22, 3, "xxx", 1, 2, 3);
+  return /* () */0;
+}
+
 function test_hi(x) {
   var match = x.hi(1, 2, 3);
   if (match !== null) {
@@ -32,6 +37,7 @@ function f(x) {
   return /* () */0;
 }
 
+exports.test = test;
 exports.test_hi = test_hi;
 exports.test_hi__2 = test_hi__2;
 exports.test_cb = test_cb;

jscomp/test/bs_splice_partial.js

@@ -8,7 +8,7 @@
 type t 
 external on_exit_slice3 : 
     int 
-    -> (_ [@bs.as 3]) 
+    -> h:(_ [@bs.as 3]) 
     -> (_ [@bs.as "xxx"]) 
     -> int array
     -> unit 
@@ -18,10 +18,10 @@ external on_exit_slice3 :
 
 
 
-(* let test _g = 
-    on_exit_slice3 __LINE__ [|1;2;3|] 
+ let test g = 
+    on_exit_slice3 __LINE__ [|1;2;3|] g
+
 
-*)    
 
 
 external hi : int array -> int option = "hi"

jscomp/test/bs_splice_partial.ml

@@ -17238,9 +17238,7 @@ type attr =
 
 type label_noname = 
   | Label
-  | LabelCst of { cst : cst }
   | Empty 
-  | EmptyCst of cst 
   | Optional
 
 type t = 
@@ -17304,9 +17302,7 @@ type cst =
 
 type label_noname = 
   | Label 
-  | LabelCst of { cst : cst  }
   | Empty 
-  | EmptyCst of cst 
   | Optional
 
 type label = 
@@ -19934,16 +19930,16 @@ let handle_attributes
                    param_type :: arg_types end
              | Labelled s  ->
                begin match refine_arg_type ~nolabel:false ty with
-                 | new_ty, (Arg_cst i as arg_type)  ->
-                   LabelCst {cst = i}, arg_type, arg_types
+                 | new_ty, (Arg_cst _ as arg_type)  ->
+                   Label , arg_type, arg_types
                  | new_ty, arg_type ->
                    Label , arg_type, 
                    {param_type with ty = new_ty} :: arg_types
                end
              | Nolabel ->
                begin match refine_arg_type ~nolabel:true ty with
-                 | new_ty , (Arg_cst i as arg_type) ->
-                   EmptyCst i , arg_type,  arg_types
+                 | new_ty , (Arg_cst _ as arg_type) ->
+                   Empty , arg_type,  arg_types
                  | new_ty , arg_type ->
                    Empty, arg_type, {param_type with ty = new_ty} :: arg_types
                end