@@ -677,7 +677,9 @@ let declaration_infos
 match elt_result with
 | Error _ -> (var_infos, member_infos, type_infos)
 | Ok elt ->
-let type_ = Ty_printer.string_of_elt ~exact_by_default elt in
+let type_ =
+Ty_printer.string_of_elt ~exact_by_default ~ts_syntax:(Context.ts_syntax cx) elt
+in
 (match kind with
 | `Declaration ->
 let declaration = Declaration.{ name; loc } in

@@ -30,7 +30,7 @@ let tests =
 obj_props = [getter];
 }
 in
-let str = Ty_printer.string_of_t ~exact_by_default:true obj in
+let str = Ty_printer.string_of_t ~exact_by_default:true ~ts_syntax:false obj in
 assert_equal ~ctxt ~printer:(fun x -> x) "{get foo(): string}" str
 );
 ( "type_object_property_set" >:: fun ctxt ->
@@ -53,12 +53,12 @@ let tests =
 obj_props = [setter];
 }
 in
-let str = Ty_printer.string_of_t ~exact_by_default:true obj in
+let str = Ty_printer.string_of_t ~exact_by_default:true ~ts_syntax:false obj in
 assert_equal ~ctxt ~printer:(fun x -> x) "{set foo(string): void}" str
 );
 ( "empty_inexact_tuple" >:: fun ctxt ->
 let tup = Ty.Tup { elements = []; inexact = true } in
-let str = Ty_printer.string_of_t tup in
+let str = Ty_printer.string_of_t ~ts_syntax:false tup in
 assert_equal ~ctxt ~printer:(fun x -> x) "[...]" str
 );
 ( "inexact_tuple" >:: fun ctxt ->
@@ -69,7 +69,7 @@ let tests =
 ]
 in
 let tup = Ty.Tup { elements; inexact = true } in
-let str = Ty_printer.string_of_t tup in
+let str = Ty_printer.string_of_t ~ts_syntax:false tup in
 assert_equal ~ctxt ~printer:(fun x -> x) "[number, ...]" str
 );
 ]

@@ -304,29 +304,29 @@ module Sorting = struct
 ( "idempotence" >:: fun ctxt ->
 assert_equal
 ~ctxt
-~printer:(Ty_printer.string_of_t ~exact_by_default:true)
+~printer:(Ty_printer.string_of_t ~exact_by_default:true ~ts_syntax:false)
 (simplify_base t0)
 (simplify_base (simplify_base t0));
 assert_equal
 ~ctxt
-~printer:(Ty_printer.string_of_t ~exact_by_default:true)
+~printer:(Ty_printer.string_of_t ~exact_by_default:true ~ts_syntax:false)
 (simplify_base t6)
 (simplify_base (simplify_base (simplify_base t6)));
 assert_equal
 ~ctxt
-~printer:(Ty_printer.string_of_t ~exact_by_default:true)
+~printer:(Ty_printer.string_of_t ~exact_by_default:true ~ts_syntax:false)
 (simplify_sort t4)
 (simplify_sort (simplify_sort t4));
 assert_equal
 ~ctxt
-~printer:(Ty_printer.string_of_t ~exact_by_default:true)
+~printer:(Ty_printer.string_of_t ~exact_by_default:true ~ts_syntax:false)
 (simplify_sort t6)
 (simplify_sort (simplify_sort (simplify_sort t6)))
 );
 ( "sorting" >:: fun ctxt ->
 assert_equal
 ~ctxt
-~printer:(Ty_printer.string_of_t ~exact_by_default:true)
+~printer:(Ty_printer.string_of_t ~exact_by_default:true ~ts_syntax:false)
 t6_sorted
 (simplify_sort t6)
 );

@@ -44,8 +44,8 @@ let variance_ = function
 (* Main Transformation *)
 (*************************)
 
-let layout_of_elt ~prefer_single_quotes ?(size = 5000) ?(with_comments = true) ~exact_by_default elt
-=
+let layout_of_elt
+~prefer_single_quotes ?(size = 5000) ?(with_comments = true) ~exact_by_default ~ts_syntax elt =
 let size = ref size in
 let local_name_of_symbol symbol =
 let { sym_name = name; sym_provenance = provenance; _ } = symbol in
@@ -537,9 +537,12 @@ let layout_of_elt ~prefer_single_quotes ?(size = 5000) ?(with_comments = true) ~
 | _ -> type_ ~depth t
 and enum_decl s = fuse [Atom "enum"; space; identifier (local_name_of_symbol s)]
 and utility ~depth u =
-let ctor = Ty.string_of_utility_ctor u in
-let ts = Ty.types_of_utility u in
-type_reference ~depth (identifier (Reason.OrdinaryName ctor)) ts
+match u with
+| ReadOnly (Tup _ as t) when ts_syntax -> fuse [Atom "readonly"; space; type_ ~depth t]
+| _ ->
+let ctor = Ty.string_of_utility_ctor u in
+let ts = Ty.types_of_utility u in
+type_reference ~depth (identifier (Reason.OrdinaryName ctor)) ts
 and type_parameter ~depth params =
 list
 ~wrap:(Atom "<", Atom ">")
@@ -661,9 +664,16 @@ let layout_of_elt ~prefer_single_quotes ?(size = 5000) ?(with_comments = true) ~
 | Decl d -> decl ~depth:0 d
 
 let layout_of_type_at_pos_types
-~prefer_single_quotes ?size ?with_comments ~exact_by_default (unevaluated, evaluated) =
+~prefer_single_quotes ?size ?with_comments ~exact_by_default ~ts_syntax (unevaluated, evaluated)
+=
 let layout_unevaluated =
-layout_of_elt ~prefer_single_quotes ?size ?with_comments ~exact_by_default unevaluated
+layout_of_elt
+~prefer_single_quotes
+?size
+?with_comments
+~exact_by_default
+~ts_syntax
+unevaluated
 in
 match (unevaluated, evaluated) with
 | (_, None) -> layout_unevaluated
@@ -676,7 +686,13 @@ let layout_of_type_at_pos_types
 | Decl (TypeAliasDecl { type_ = Some t; _ }) -> Type t
 | x -> x
 in
-layout_of_elt ~prefer_single_quotes ?size ?with_comments ~exact_by_default evaluated
+layout_of_elt
+~prefer_single_quotes
+?size
+?with_comments
+~exact_by_default
+~ts_syntax
+evaluated
 in
 fuse [layout_unevaluated; hardline; Atom "="; space; layout_evaluated]
 
@@ -702,31 +718,58 @@ let print_single_line ~source_maps node =
 let print_pretty ~source_maps node = Pretty_printer.print ~source_maps ~skip_endline:true node
 
 let string_of_elt
-?(prefer_single_quotes = false) ?(with_comments = true) (elt : Ty.elt) ~exact_by_default :
- string =
-layout_of_elt ~prefer_single_quotes ~with_comments ~exact_by_default elt
+?(prefer_single_quotes = false)
+?(with_comments = true)
+~exact_by_default
+~ts_syntax
+(elt : Ty.elt) : string =
+layout_of_elt ~prefer_single_quotes ~with_comments ~exact_by_default ~ts_syntax elt
 |> print_pretty ~source_maps:None
 |> Source.contents
 
 let string_of_elt_single_line
-?(prefer_single_quotes = false) ?(with_comments = true) ?(exact_by_default = true) (elt : Ty.elt)
-=
-layout_of_elt ~prefer_single_quotes ~with_comments ~exact_by_default elt
+?(prefer_single_quotes = false)
+?(with_comments = true)
+?(exact_by_default = true)
+~ts_syntax
+(elt : Ty.elt) =
+layout_of_elt ~prefer_single_quotes ~with_comments ~exact_by_default ~ts_syntax elt
 |> print_single_line ~source_maps:None
 |> Source.contents
 
 let string_of_t
-?(prefer_single_quotes = false) ?(with_comments = true) ?(exact_by_default = true) (ty : Ty.t) =
-string_of_elt ~prefer_single_quotes ~with_comments ~exact_by_default (Ty.Type ty)
+?(prefer_single_quotes = false)
+?(with_comments = true)
+?(exact_by_default = true)
+~ts_syntax
+(ty : Ty.t) =
+string_of_elt ~prefer_single_quotes ~with_comments ~exact_by_default ~ts_syntax (Ty.Type ty)
 
 let string_of_t_single_line
-?(prefer_single_quotes = false) ?(with_comments = true) ?(exact_by_default = true) (ty : Ty.t) =
-string_of_elt_single_line ~prefer_single_quotes ~with_comments ~exact_by_default (Ty.Type ty)
+?(prefer_single_quotes = false)
+?(with_comments = true)
+?(exact_by_default = true)
+~ts_syntax
+(ty : Ty.t) =
+string_of_elt_single_line
+~prefer_single_quotes
+~with_comments
+~exact_by_default
+~ts_syntax
+(Ty.Type ty)
 
 let string_of_decl_single_line
-?(prefer_single_quotes = false) ?(with_comments = true) ?(exact_by_default = true) (d : Ty.decl)
-=
-string_of_elt_single_line ~prefer_single_quotes ~with_comments ~exact_by_default (Ty.Decl d)
+?(prefer_single_quotes = false)
+?(with_comments = true)
+?(exact_by_default = true)
+~ts_syntax
+(d : Ty.decl) =
+string_of_elt_single_line
+~prefer_single_quotes
+~with_comments
+~exact_by_default
+~ts_syntax
+(Ty.Decl d)
 
 let string_of_symbol_set syms =
 LocSymbolSet.elements syms
@@ -745,10 +788,11 @@ let string_of_type_at_pos_result
 ?(prefer_single_quotes = false)
 ?(with_comments = true)
 ?(exact_by_default = true)
+~ts_syntax
 { Ty.unevaluated; evaluated; refs } =
 let type_str =
 (unevaluated, evaluated)
-|> layout_of_type_at_pos_types ~prefer_single_quotes ~with_comments ~exact_by_default
+|> layout_of_type_at_pos_types ~prefer_single_quotes ~with_comments ~exact_by_default ~ts_syntax
 |> print_pretty ~source_maps:None
 |> Source.contents
 in

@@ -10,24 +10,50 @@ val better_quote : prefer_single_quotes:bool -> string -> string
 val property_key_quotes_needed : string -> bool
 
 val string_of_elt :
-?prefer_single_quotes:bool -> ?with_comments:bool -> Ty.elt -> exact_by_default:bool -> string
+?prefer_single_quotes:bool ->
+?with_comments:bool ->
+exact_by_default:bool ->
+ts_syntax:bool ->
+Ty.elt ->
+string
 
 val string_of_elt_single_line :
-?prefer_single_quotes:bool -> ?with_comments:bool -> ?exact_by_default:bool -> Ty.elt -> string
+?prefer_single_quotes:bool ->
+?with_comments:bool ->
+?exact_by_default:bool ->
+ts_syntax:bool ->
+Ty.elt ->
+string
 
 val string_of_decl_single_line :
-?prefer_single_quotes:bool -> ?with_comments:bool -> ?exact_by_default:bool -> Ty.decl -> string
+?prefer_single_quotes:bool ->
+?with_comments:bool ->
+?exact_by_default:bool ->
+ts_syntax:bool ->
+Ty.decl ->
+string
 
 val string_of_t :
-?prefer_single_quotes:bool -> ?with_comments:bool -> ?exact_by_default:bool -> Ty.t -> string
+?prefer_single_quotes:bool ->
+?with_comments:bool ->
+?exact_by_default:bool ->
+ts_syntax:bool ->
+Ty.t ->
+string
 
 val string_of_t_single_line :
-?prefer_single_quotes:bool -> ?with_comments:bool -> ?exact_by_default:bool -> Ty.t -> string
+?prefer_single_quotes:bool ->
+?with_comments:bool ->
+?exact_by_default:bool ->
+ts_syntax:bool ->
+Ty.t ->
+string
 
 val string_of_type_at_pos_result :
 ?prefer_single_quotes:bool ->
 ?with_comments:bool ->
 ?exact_by_default:bool ->
+ts_syntax:bool ->
 Ty.type_at_pos_result ->
 string * (string * Loc.t) list option
 

@@ -535,7 +535,12 @@ let infer_type filename content line col js_config_object :
 | FailureUnparseable (loc, _, _) ->
 (loc, Error "Unparseable", refining_locs, refinement_invalidated)
 | Success (loc, result) ->
-let (result, _) = Ty_printer.string_of_type_at_pos_result ~exact_by_default:true result in
+let (result, _) =
+Ty_printer.string_of_type_at_pos_result
+~exact_by_default:true
+~ts_syntax:(Context.ts_syntax cx)
+result
+in
 (loc, Ok result, refining_locs, refinement_invalidated)
 end
 
@@ -627,7 +632,9 @@ let dump_types js_file js_content js_config_object =
 )
 in
 let (cx, typed_ast) = infer_and_merge ~root filename js_config_object docblock ast file_sig in
-let printer = Ty_printer.string_of_elt_single_line ~exact_by_default:true in
+let printer =
+Ty_printer.string_of_elt_single_line ~exact_by_default:true ~ts_syntax:(Context.ts_syntax cx)
+in
 let types =
 Query_types.dump_types
 ~printer

@@ -695,6 +695,7 @@ let infer_type_to_response
 ~json
 ~expanded
 ~exact_by_default
+~ts_syntax
 ~strip_root
 loc
 refining_locs
@@ -709,7 +710,11 @@ let infer_type_to_response
 let open Hh_json in
 let type_json t =
 let json_obj =
-[("type", JSON_String (Ty_printer.string_of_elt_single_line ~exact_by_default t))]
+[
+( "type",
+JSON_String (Ty_printer.string_of_elt_single_line ~exact_by_default ~ts_syntax t)
+);
+]
 in
 let json_obj =
 if expanded then
@@ -730,7 +735,9 @@ let infer_type_to_response
 else
 ServerProt.Response.InferType.Friendly
 (Base.Option.map tys ~f:(fun r ->
-let (type_str, refs) = Ty_printer.string_of_type_at_pos_result ~exact_by_default r in
+let (type_str, refs) =
+Ty_printer.string_of_type_at_pos_result ~exact_by_default ~ts_syntax r
+in
 { ServerProt.Response.InferType.type_str; refs }
 )
 )
@@ -891,6 +898,7 @@ let infer_type
 ~json
 ~expanded
 ~exact_by_default
+~ts_syntax:(Options.ts_syntax options)
 ~strip_root
 loc
 refining_locs
@@ -969,6 +977,7 @@ let inlay_hint
 let (type_str, refs) =
 Ty_printer.string_of_type_at_pos_result
 ~exact_by_default:(Options.exact_by_default options)
+~ts_syntax:(Options.ts_syntax options)
 r
 in
 { ServerProt.Response.InferType.type_str; refs }