diff --git a/infer/src/base/Config.ml b/infer/src/base/Config.ml
index 1cbaff121..fcdd1df5a 100644
--- a/infer/src/base/Config.ml
+++ b/infer/src/base/Config.ml
@@ -2617,13 +2617,11 @@ and (_ : bool ref) =
 
 let inferconfig_dir =
   let rec find dir =
-    match Sys.file_exists ~follow_symlinks:false (dir ^/ CommandDoc.inferconfig_file) with
-    | `Yes ->
-        Some dir
-    | `No | `Unknown ->
-        let parent = Filename.dirname dir in
-        let is_root = String.equal dir parent in
-        if is_root then None else find parent
+    if ISys.file_exists ~follow_symlinks:false (dir ^/ CommandDoc.inferconfig_file) then Some dir
+    else
+      let parent = Filename.dirname dir in
+      let is_root = String.equal dir parent in
+      if is_root then None else find parent
   in
   find (Sys.getcwd ())
 
diff --git a/infer/src/base/DB.ml b/infer/src/base/DB.ml
index 18cc6a17c..b5bcecb36 100644
--- a/infer/src/base/DB.ml
+++ b/infer/src/base/DB.ml
@@ -7,7 +7,6 @@
  *)
 
 open! IStd
-open PolyVariantEqual
 
 (** Database of analysis results *)
 
@@ -76,7 +75,7 @@ let filename_from_string s = s
 
 let filename_add_suffix fn s = fn ^ s
 
-let file_exists path = Sys.file_exists path = `Yes
+let file_exists path = ISys.file_exists path
 
 (** Return the time when a file was last modified. The file must exist. *)
 let file_modified_time ?(symlink = false) fname =
diff --git a/infer/src/base/Logging.ml b/infer/src/base/Logging.ml
index 0df5ec65f..f5cae5f69 100644
--- a/infer/src/base/Logging.ml
+++ b/infer/src/base/Logging.ml
@@ -361,7 +361,7 @@ let setup_log_file () =
         let logfile_path =
           ResultsDirEntryName.get_path ~results_dir:Config.toplevel_results_dir Logs
         in
-        let preexisting_logfile = PolyVariantEqual.( = ) (Sys.file_exists logfile_path) `Yes in
+        let preexisting_logfile = ISys.file_exists logfile_path in
         let chan = Stdlib.open_out_gen [Open_append; Open_creat] 0o666 logfile_path in
         let file_fmt =
           let f = F.formatter_of_out_channel chan in
diff --git a/infer/src/base/PerfEvent.ml b/infer/src/base/PerfEvent.ml
index 6df7443e8..d2cfd5b8c 100644
--- a/infer/src/base/PerfEvent.ml
+++ b/infer/src/base/PerfEvent.ml
@@ -229,7 +229,7 @@ let logger =
      in
      let is_toplevel_process = CommandLineOption.is_originator && not !ProcessPoolState.in_child in
      ( if is_toplevel_process then
-       let preexisting_logfile = PolyVariantEqual.( = ) (Sys.file_exists log_file) `Yes in
+       let preexisting_logfile = ISys.file_exists log_file in
        if preexisting_logfile then Unix.unlink log_file ) ;
      let out_channel = Stdlib.open_out_gen [Open_append; Open_creat] 0o666 log_file in
      let logger = F.formatter_of_out_channel out_channel in
diff --git a/infer/src/base/ResultsDir.ml b/infer/src/base/ResultsDir.ml
index ac6ac3485..a2dd1b3dc 100644
--- a/infer/src/base/ResultsDir.ml
+++ b/infer/src/base/ResultsDir.ml
@@ -44,7 +44,7 @@ module RunState = struct
                 Was it created using an older version of infer?" Config.results_dir err_msg) )
         msg
     in
-    if PolyVariantEqual.(Sys.file_exists state_file_path <> `Yes) then
+    if not (ISys.file_exists state_file_path) then
       error "save state not found: '%s' does not exist" state_file_path
     else
       match Atdgen_runtime.Util.Json.from_file Runstate_j.read_t state_file_path with
diff --git a/infer/src/base/SourceFile.ml b/infer/src/base/SourceFile.ml
index 6176227ee..530622165 100644
--- a/infer/src/base/SourceFile.ml
+++ b/infer/src/base/SourceFile.ml
@@ -6,7 +6,6 @@
  *)
 
 open! IStd
-open PolyVariantEqual
 module L = Logging
 
 type t =
@@ -169,7 +168,7 @@ let exists_cache = String.Table.create ~size:256 ()
 let path_exists abs_path =
   try String.Table.find_exn exists_cache abs_path
   with Not_found_s _ | Caml.Not_found ->
-    let result = Sys.file_exists abs_path = `Yes in
+    let result = ISys.file_exists abs_path in
     String.Table.set exists_cache ~key:abs_path ~data:result ;
     result
 
diff --git a/infer/src/base/Utils.ml b/infer/src/base/Utils.ml
index 26bfd7e84..a58a0560c 100644
--- a/infer/src/base/Utils.ml
+++ b/infer/src/base/Utils.ml
@@ -447,7 +447,7 @@ let get_available_memory_MB () =
       try Scanf.sscanf line "MemAvailable: %u kB" (fun mem_kB -> Some (mem_kB / 1024))
       with Scanf.Scan_failure _ -> scan_for_expected_output in_channel )
   in
-  if Sys.file_exists proc_meminfo <> `Yes then None
+  if not (ISys.file_exists proc_meminfo) then None
   else with_file_in proc_meminfo ~f:scan_for_expected_output
 
 
diff --git a/infer/src/clang/ClangWrapper.ml b/infer/src/clang/ClangWrapper.ml
index 1d7eabf92..ec75cdd44 100644
--- a/infer/src/clang/ClangWrapper.ml
+++ b/infer/src/clang/ClangWrapper.ml
@@ -37,10 +37,7 @@ let check_for_existing_file args =
                  Create empty file empty file and pass that to clang. This is to enable compilation to continue *)
               match List.hd rest with
               | Some arg ->
-                  if
-                    Str.string_match clang_ignore_regex arg 0
-                    && PolyVariantEqual.(Sys.file_exists arg <> `Yes)
-                  then (
+                  if Str.string_match clang_ignore_regex arg 0 && not (ISys.file_exists arg) then (
                     Unix.mkdir_p (Filename.dirname arg) ;
                     let file = Unix.openfile ~mode:[Unix.O_CREAT; Unix.O_RDONLY] arg in
                     Unix.close file )
diff --git a/infer/src/integration/Buck.ml b/infer/src/integration/Buck.ml
index fc0bd8387..74d486ac7 100644
--- a/infer/src/integration/Buck.ml
+++ b/infer/src/integration/Buck.ml
@@ -371,7 +371,7 @@ let inline_argument_files buck_args =
   let expand_buck_arg buck_arg =
     if String.is_prefix ~prefix:"@" buck_arg then
       let file_name = String.chop_prefix_exn ~prefix:"@" buck_arg in
-      if PolyVariantEqual.(Sys.file_exists file_name <> `Yes) then [buck_arg]
+      if not (ISys.file_exists file_name) then [buck_arg]
         (* Arguments that start with @ could mean something different than an arguments file in buck. *)
       else
         let expanded_args =
diff --git a/infer/src/integration/BuckFlavors.ml b/infer/src/integration/BuckFlavors.ml
index 26a069c3d..e30ed082d 100644
--- a/infer/src/integration/BuckFlavors.ml
+++ b/infer/src/integration/BuckFlavors.ml
@@ -48,10 +48,9 @@ let run_buck_build prog buck_build_args =
         let dirname = Filename.dirname full_path in
         let get_path results_dir = ResultsDirEntryName.get_path ~results_dir CaptureDependencies in
         (* Buck can either give the full path to infer-deps.txt ... *)
-        if PolyVariantEqual.(Sys.file_exists (get_path dirname) = `Yes) then get_path dirname :: acc
+        if ISys.file_exists (get_path dirname) then get_path dirname :: acc
           (* ... or a folder which contains infer-deps.txt *)
-        else if PolyVariantEqual.(Sys.file_exists (get_path full_path) = `Yes) then
-          get_path full_path :: acc
+        else if ISys.file_exists (get_path full_path) then get_path full_path :: acc
         else acc
     | _ ->
         L.internal_error "Couldn't parse buck target output: %s@\n" line ;
@@ -69,9 +68,7 @@ let merge_deps_files depsfiles =
           Utils.fold_folders ~init:[] ~path:buck_out ~f:(fun acc dir ->
               if
                 String.is_substring dir ~substring:"infer-out"
-                && PolyVariantEqual.(
-                     Sys.file_exists (ResultsDirEntryName.get_path ~results_dir:dir CaptureDB)
-                     = `Yes)
+                && ISys.file_exists (ResultsDirEntryName.get_path ~results_dir:dir CaptureDB)
               then Printf.sprintf "\t\t%s" dir :: acc
               else acc )
         in
diff --git a/infer/src/integration/BuckJavaFlavor.ml b/infer/src/integration/BuckJavaFlavor.ml
index f854ee6ab..418182ea6 100644
--- a/infer/src/integration/BuckJavaFlavor.ml
+++ b/infer/src/integration/BuckJavaFlavor.ml
@@ -93,23 +93,19 @@ let expand_target acc (target, target_path) =
   let expand_dir acc (target, target_path) =
     (* invariant: [target_path] is absolute *)
     let db_file = ResultsDirEntryName.get_path ~results_dir:target_path CaptureDB in
-    match Sys.file_exists db_file with
-    | `Yes ->
-        (* there is a capture DB at this path, so terminate expansion and generate deps line *)
-        let line = Printf.sprintf "%s\t-\t%s" target target_path in
-        line :: acc
-    | `No | `Unknown -> (
-        (* no capture DB was found, so look for, and inline, an [infer-deps.txt] file *)
-        let infer_deps =
-          ResultsDirEntryName.get_path ~results_dir:target_path CaptureDependencies
-        in
-        match Sys.file_exists infer_deps with
-        | `Yes ->
-            Utils.with_file_in infer_deps
-              ~f:(In_channel.fold_lines ~init:acc ~f:(fun acc line -> line :: acc))
-        | `No | `Unknown ->
-            L.internal_error "No capture DB or infer-deps file in %s@." target_path ;
-            acc )
+    if ISys.file_exists db_file then
+      (* there is a capture DB at this path, so terminate expansion and generate deps line *)
+      let line = Printf.sprintf "%s\t-\t%s" target target_path in
+      line :: acc
+    else
+      (* no capture DB was found, so look for, and inline, an [infer-deps.txt] file *)
+      let infer_deps = ResultsDirEntryName.get_path ~results_dir:target_path CaptureDependencies in
+      if ISys.file_exists infer_deps then
+        Utils.with_file_in infer_deps
+          ~f:(In_channel.fold_lines ~init:acc ~f:(fun acc line -> line :: acc))
+      else (
+        L.internal_error "No capture DB or infer-deps file in %s@." target_path ;
+        acc )
   in
   let target_path =
     if Filename.is_absolute target_path then target_path else Config.project_root ^/ target_path
diff --git a/infer/src/integration/Driver.ml b/infer/src/integration/Driver.ml
index 6dca609c2..24bc755d0 100644
--- a/infer/src/integration/Driver.ml
+++ b/infer/src/integration/Driver.ml
@@ -5,7 +5,6 @@
  * LICENSE file in the root directory of this source tree.
  *)
 open! IStd
-open PolyVariantEqual
 
 (** entry points for top-level functionalities such as capture, analysis, and reporting *)
 
@@ -85,7 +84,7 @@ let reset_duplicates_file () =
   let create () =
     Unix.close (Unix.openfile ~perm:0o0666 ~mode:[Unix.O_CREAT; Unix.O_WRONLY] start)
   in
-  if Sys.file_exists start = `Yes then delete () ;
+  if ISys.file_exists start then delete () ;
   create ()
 
 
diff --git a/infer/src/integration/Gradle.ml b/infer/src/integration/Gradle.ml
index 667cca5ef..b571c6ca2 100644
--- a/infer/src/integration/Gradle.ml
+++ b/infer/src/integration/Gradle.ml
@@ -18,7 +18,7 @@ type fold_state = {files: string list; opts: string list; opt_st: string list; f
 (* see GradleTest.ml *)
 let parse_gradle_line ~line =
   let concat_st lst st = if List.is_empty st then lst else String.concat ~sep:" " st :: lst in
-  let file_exist file = PolyVariantEqual.(Sys.file_exists file = `Yes) in
+  let file_exist file = ISys.file_exists file in
   let rev_args = line |> String.strip |> String.split ~on:' ' |> List.rev in
   let res =
     List.fold rev_args ~init:{files= []; opts= []; opt_st= []; file_st= []}
diff --git a/infer/src/istd/ISys.ml b/infer/src/istd/ISys.ml
new file mode 100644
index 000000000..495244a94
--- /dev/null
+++ b/infer/src/istd/ISys.ml
@@ -0,0 +1,11 @@
+(*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *)
+
+open! IStd
+
+let file_exists ?follow_symlinks path =
+  match Sys.file_exists ?follow_symlinks path with `Yes -> true | `No | `Unknown -> false
diff --git a/infer/src/istd/ISys.mli b/infer/src/istd/ISys.mli
new file mode 100644
index 000000000..da53ccdfb
--- /dev/null
+++ b/infer/src/istd/ISys.mli
@@ -0,0 +1,12 @@
+(*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *)
+
+open! IStd
+
+val file_exists : ?follow_symlinks:bool -> string -> bool
+(** Similar to [Sys.file_exists_exn], but it returns [false] when the result is unknown, instead of
+    raising an exception. [follow_symlinks] is true by default. *)
diff --git a/infer/src/java/jClasspath.ml b/infer/src/java/jClasspath.ml
index 6aee8c551..fd679347b 100644
--- a/infer/src/java/jClasspath.ml
+++ b/infer/src/java/jClasspath.ml
@@ -15,12 +15,10 @@ let split_classpath = String.split ~on:JFile.sep
 let classpath_of_paths paths =
   let of_path path =
     let full_path = Utils.filename_to_absolute ~root:Config.project_root path in
-    match Sys.file_exists full_path with
-    | `Yes ->
-        Some full_path
-    | _ ->
-        L.debug Capture Medium "Path %s not found" full_path ;
-        None
+    if ISys.file_exists full_path then Some full_path
+    else (
+      L.debug Capture Medium "Path %s not found" full_path ;
+      None )
   in
   let string_sep = Char.to_string JFile.sep in
   List.filter_map paths ~f:of_path |> String.concat ~sep:string_sep
diff --git a/infer/src/java/jFrontend.ml b/infer/src/java/jFrontend.ml
index 6c5d4e167..a5204d1a2 100644
--- a/infer/src/java/jFrontend.ml
+++ b/infer/src/java/jFrontend.ml
@@ -7,7 +7,6 @@
  *)
 
 open! IStd
-open PolyVariantEqual
 open Javalib_pack
 open Sawja_pack
 module L = Logging
@@ -124,7 +123,7 @@ let cache_classname cn =
     split [] (Filename.dirname path)
   in
   let rec mkdir l p =
-    let () = if Sys.file_exists p <> `Yes then Unix.mkdir p ~perm:493 in
+    let () = if not (ISys.file_exists p) then Unix.mkdir p ~perm:493 in
     match l with [] -> () | d :: tl -> mkdir tl (Filename.concat p d)
   in
   mkdir splitted_root_dir Filename.dir_sep ;
@@ -133,7 +132,7 @@ let cache_classname cn =
   Out_channel.close file_out
 
 
-let is_classname_cached cn = Sys.file_exists (path_of_cached_classname cn) = `Yes
+let is_classname_cached cn = ISys.file_exists (path_of_cached_classname cn)
 
 let test_source_file_location source_file program cn node =
   let is_synthetic = function
diff --git a/infer/src/java/jMain.ml b/infer/src/java/jMain.ml
index 1ef2fc958..a3f3ed4f5 100644
--- a/infer/src/java/jMain.ml
+++ b/infer/src/java/jMain.ml
@@ -7,7 +7,6 @@
  *)
 
 open! IStd
-open PolyVariantEqual
 open Javalib_pack
 module L = Logging
 
@@ -111,7 +110,7 @@ let do_all_files sources program =
 
 (* loads the source files and translates them *)
 let main load_sources_and_classes =
-  ( match (Config.biabduction_models_mode, Sys.file_exists Config.biabduction_models_jar = `Yes) with
+  ( match (Config.biabduction_models_mode, ISys.file_exists Config.biabduction_models_jar) with
   | true, false ->
       ()
   | false, false ->
diff --git a/infer/src/java/jModels.ml b/infer/src/java/jModels.ml
index 331e791bb..37a7065e4 100644
--- a/infer/src/java/jModels.ml
+++ b/infer/src/java/jModels.ml
@@ -34,7 +34,7 @@ let collect_specs_filenames jar_filename =
 
 let load_models ~jar_filename =
   match !models_jar with
-  | None when match Sys.file_exists jar_filename with `Yes -> false | _ -> true ->
+  | None when not (ISys.file_exists jar_filename) ->
       L.die InternalError "Java model file not found@."
   | None ->
       models_jar := Some jar_filename ;