fix #4572

Author: bobzhang

jscomp/syntax/ast_derive_js_mapper.ml

@@ -72,9 +72,10 @@ let eraseTypeStr =
     )
 let unsafeIndex = "_index"    
 let unsafeIndexGet = 
+  let any = Typ.any () in   
   Str.primitive
     (Val.mk ~prim:[""] {loc = noloc; txt = unsafeIndex} ~attrs:[Ast_attributes.bs_get_index]
-       (Ast_compatible.arrow (Typ.var "b") (Ast_compatible.arrow (Typ.var "a") (Typ.var "c")))
+       (Ast_compatible.arrow any (Ast_compatible.arrow any any))
     )
 let unsafeIndexGetExp = (Exp.ident {loc = noloc; txt = Lident unsafeIndex}) 
 (* JavaScript has allowed trailing commas in array literals since the beginning, 

jscomp/syntax/ast_external_process.ml

@@ -100,21 +100,24 @@ let refine_arg_type ~(nolabel:bool) (ptyp : Ast_core_type.t)
   (if ptyp.ptyp_desc = Ptyp_any then 
      let ptyp_attrs = ptyp.ptyp_attributes in
      let result = Ast_attributes.iter_process_bs_string_or_int_as ptyp_attrs in
-     (* when ppx start dropping attributes
-        we should warn, there is a trade off whether
-        we should warn dropped non bs attribute or not
-     *)
-     Bs_ast_invariant.warn_discarded_unused_attributes ptyp_attrs;
      match result with
      |  None ->
-       Bs_syntaxerr.err ptyp.ptyp_loc Invalid_underscore_type_in_external
-     | Some (Int i) -> (* (_[@bs.as ])*)
-       (* This type is used in bs.obj only to construct obj type*)
-       Arg_cst(External_arg_spec.cst_int i)
-     | Some (Str i)->
-       Arg_cst (External_arg_spec.cst_string i)     
-     | Some (Js_literal_str s) ->
-       Arg_cst (External_arg_spec.cst_obj_literal  s)
+       spec_of_ptyp nolabel ptyp
+     | Some cst  -> (* (_[@bs.as ])*)
+       (* when ppx start dropping attributes
+          we should warn, there is a trade off whether
+          we should warn dropped non bs attribute or not
+       *)
+       Bs_ast_invariant.warn_discarded_unused_attributes ptyp_attrs;
+       begin match cst with 
+         | Int i -> 
+           (* This type is used in bs.obj only to construct obj type*)
+           Arg_cst(External_arg_spec.cst_int i)
+         | Str i->
+           Arg_cst (External_arg_spec.cst_string i)     
+         |  Js_literal_str s ->
+           Arg_cst (External_arg_spec.cst_obj_literal  s)
+       end
    else (* ([`a|`b] [@bs.string]) *)
      spec_of_ptyp nolabel ptyp   
   )

jscomp/test/build.ninja

@@ -328,6 +328,7 @@ build test/gpr_4442_test.cmi test/gpr_4442_test.cmj : cc test/gpr_4442_test.ml |
 build test/gpr_4491_test.cmi test/gpr_4491_test.cmj : cc test/gpr_4491_test.ml | $stdlib
 build test/gpr_4494_test.cmi test/gpr_4494_test.cmj : cc test/gpr_4494_test.ml | $stdlib
 build test/gpr_4519_test.cmi test/gpr_4519_test.cmj : cc test/gpr_4519_test.ml | test/mt.cmj $stdlib
+build test/gpr_4572_test.cmi test/gpr_4572_test.cmj : cc test/gpr_4572_test.ml | $stdlib
 build test/gpr_459_test.cmi test/gpr_459_test.cmj : cc test/gpr_459_test.ml | test/mt.cmj $stdlib
 build test/gpr_627_test.cmi test/gpr_627_test.cmj : cc test/gpr_627_test.ml | test/mt.cmj $stdlib
 build test/gpr_658.cmi test/gpr_658.cmj : cc test/gpr_658.ml | $stdlib