diff --git a/infer/src/IR/LintIssues.ml b/infer/src/IR/LintIssues.ml
index b3099dd33..d763f4c1a 100644
--- a/infer/src/IR/LintIssues.ml
+++ b/infer/src/IR/LintIssues.ml
@@ -52,5 +52,5 @@ let load_issues_to_errlog_map dir =
           ) !errLogMap map
     | None -> () in
   match children_opt with
-  | Some children -> Array.iter load_issues_to_map children
+  | Some children -> Array.iter ~f:load_issues_to_map children
   | None -> ()
diff --git a/infer/src/backend/dotty.ml b/infer/src/backend/dotty.ml
index ecc32afbd..16fb046b4 100644
--- a/infer/src/backend/dotty.ml
+++ b/infer/src/backend/dotty.ml
@@ -106,13 +106,12 @@ let print_stack_info = ref false
 
 (* replace a dollar sign in a name with a D. We need this because dotty get confused if there is*)
 (* a dollar sign i a label*)
-let strip_special_chars s =
-  let b = Bytes.of_string s in
+let strip_special_chars b =
   let replace st c c' =
-    if Bytes.contains st c then begin
-      let idx = Bytes.index st c in
+    if String.contains st c then begin
+      let idx = String.index_exn st c in
       try
-        Bytes.set st idx c';
+        String.set st idx c';
         st
       with Invalid_argument _ -> L.out "@\n@\n Invalid argument!!! @\n @.@.@."; assert false
     end else st in
@@ -124,7 +123,7 @@ let strip_special_chars s =
   let s5 = replace s4 ')' 'B' in
   let s6 = replace s5 '+' 'P' in
   let s7 = replace s6 '-' 'M' in
-  Bytes.to_string s7
+  s7
 
 let rec strexp_to_string pe coo f se =
   match se with
diff --git a/infer/src/backend/mergeCapture.ml b/infer/src/backend/mergeCapture.ml
index 20165682d..e332cd824 100644
--- a/infer/src/backend/mergeCapture.ml
+++ b/infer/src/backend/mergeCapture.ml
@@ -113,7 +113,7 @@ let rec slink ~stats ~skiplevels src dst =
       then Unix.mkdir dst ~perm:0o700;
       let items = Sys.readdir src in
       Array.iter
-        (fun item ->
+        ~f:(fun item ->
            slink ~stats ~skiplevels:(skiplevels - 1)
              (Filename.concat src item) (Filename.concat dst item))
         items
diff --git a/infer/src/base/DB.ml b/infer/src/base/DB.ml
index fde62dd6d..272de84ed 100644
--- a/infer/src/base/DB.ml
+++ b/infer/src/base/DB.ml
@@ -188,8 +188,8 @@ module Results_dir = struct
 
   let clean_specs_dir () =
     create_dir specs_dir; (* create dir just in case it doesn't exist to avoid errors *)
-    let files_to_remove = Array.map (Filename.concat specs_dir) (Sys.readdir specs_dir) in
-    Array.iter Sys.remove files_to_remove
+    let files_to_remove = Array.map ~f:(Filename.concat specs_dir) (Sys.readdir specs_dir) in
+    Array.iter ~f:Sys.remove files_to_remove
 
   (** create a file at the given path, creating any missing directories *)
   let create_file pk path =
@@ -245,13 +245,13 @@ let mark_file_updated fname =
 (** Fold over all file paths recursively under [dir] which match [p]. *)
 let fold_paths_matching ~dir ~p ~init ~f =
   let rec paths path_list dir =
-    Array.fold_left
-      (fun acc file ->
+    Array.fold
+      ~f:(fun acc file ->
          let path = dir // file in
          if Sys.is_directory path = `Yes then (paths acc path)
          else if p path then f path acc
          else acc)
-      path_list
+      ~init:path_list
       (Sys.readdir dir) in
   paths init dir
 
diff --git a/infer/src/base/StatisticsToolbox.re b/infer/src/base/StatisticsToolbox.re
index 68d78774b..700631836 100644
--- a/infer/src/base/StatisticsToolbox.re
+++ b/infer/src/base/StatisticsToolbox.re
@@ -51,7 +51,7 @@ let compute_statistics values => {
   let average = sum /. float_of_int num_elements;
   let values_arr = Array.of_list values;
   Array.sort
-    (
+    cmp::(
       fun a b =>
         if (a == b) {
           0
diff --git a/infer/src/base/Utils.ml b/infer/src/base/Utils.ml
index e63d548e5..50ddfc655 100644
--- a/infer/src/base/Utils.ml
+++ b/infer/src/base/Utils.ml
@@ -10,7 +10,10 @@
 
 (** General utility functions and definition with global scope *)
 
+module Arg = Core.Std.Arg
+module Array = Core.Std.Array
 module Bool = Core.Std.Bool
+module Bytes = Core.Std.Bytes
 module Caml = Core.Std.Caml
 module Filename = Core.Std.Filename
 module Fn = Core.Std.Fn
@@ -465,7 +468,7 @@ let directory_fold f init path =
     match dirs with
     | [] -> accu
     | d:: tl ->
-        let (new_accu, new_dirs) = Array.fold_left (collect d) (accu, tl) (Sys.readdir d) in
+        let (new_accu, new_dirs) = Array.fold ~f:(collect d) ~init:(accu, tl) (Sys.readdir d) in
         loop new_accu new_dirs in
   if Sys.is_directory path = `Yes then
     loop init [path]
@@ -488,7 +491,7 @@ let directory_iter f path =
     match dirs with
     | [] -> ()
     | d:: tl ->
-        let new_dirs = Array.fold_left (apply d) tl (Sys.readdir d) in
+        let new_dirs = Array.fold ~f:(apply d) ~init:tl (Sys.readdir d) in
         loop new_dirs in
   if Sys.is_directory path = `Yes then
     loop [path]
diff --git a/infer/src/base/Utils.mli b/infer/src/base/Utils.mli
index f8fdb8925..94a2d0807 100644
--- a/infer/src/base/Utils.mli
+++ b/infer/src/base/Utils.mli
@@ -10,7 +10,10 @@
 
 (** General utility functions *)
 
+module Arg = Core.Std.Arg
+module Array = Core.Std.Array
 module Bool = Core.Std.Bool
+module Bytes = Core.Std.Bytes
 module Caml = Core.Std.Caml
 module Filename = Core.Std.Filename
 module Fn = Core.Std.Fn
diff --git a/infer/src/clang/cTrans_utils.ml b/infer/src/clang/cTrans_utils.ml
index 4528901c9..597c7b08e 100644
--- a/infer/src/clang/cTrans_utils.ml
+++ b/infer/src/clang/cTrans_utils.ml
@@ -515,7 +515,7 @@ let define_condition_side_effects e_cond instrs_cond sil_loc =
 
 let fix_param_exps_mismatch params_stmt exps_param =
   let diff = IList.length params_stmt - IList.length exps_param in
-  let args = if diff >0 then Array.make diff dummy_exp
+  let args = if diff >0 then Array.create ~len:diff dummy_exp
     else assert false in
   let exps'= exps_param @ (Array.to_list args) in
   exps'
diff --git a/infer/src/java/jFrontend.ml b/infer/src/java/jFrontend.ml
index ebdd52c2c..de734156e 100644
--- a/infer/src/java/jFrontend.ml
+++ b/infer/src/java/jFrontend.ml
@@ -71,7 +71,7 @@ let add_edges
   if not super_call then
     (* the exceptions node is just before the exit node *)
     Procdesc.node_set_succs_exn context.procdesc exn_node exit_nodes exit_nodes;
-  Array.iteri connect_nodes method_body_nodes
+  Array.iteri ~f:connect_nodes method_body_nodes
 
 
 (** Add a concrete method. *)
@@ -90,7 +90,7 @@ let add_cmethod source_file program linereader icfg cm proc_name =
       let instrs = JBir.code jbir_code in
       let context =
         JContext.create_context icfg procdesc jbir_code cn source_file program in
-      let method_body_nodes = Array.mapi (JTrans.instruction context) instrs in
+      let method_body_nodes = Array.mapi ~f:(JTrans.instruction context) instrs in
       add_edges context start_node exn_node [exit_node] method_body_nodes jbir_code false
 
 
diff --git a/infer/src/java/jTrans.ml b/infer/src/java/jTrans.ml
index e998db67d..2db8c44ff 100644
--- a/infer/src/java/jTrans.ml
+++ b/infer/src/java/jTrans.ml
@@ -172,11 +172,11 @@ let translate_locals program tenv formals bytecode jbir_code =
   (* TODO (#4040807): Needs to add the JBir temporary variables since other parts of the
      code are still relying on those *)
   let with_jbir_vars =
-    Array.fold_left
-      (fun accu jbir_var ->
+    Array.fold
+      ~f:(fun accu jbir_var ->
          let var = Mangled.from_string (JBir.var_name_g jbir_var) in
          collect accu (var, Typ.Tvoid))
-      with_bytecode_vars
+      ~init:with_bytecode_vars
       (JBir.vars jbir_code) in
   snd with_jbir_vars
 
@@ -245,7 +245,7 @@ let get_implementation cm =
       let bytecode = Lazy.force t in
       let c_code =
         Array.map
-          (function
+          ~f:(function
             | (JCode.OpInvoke (`Dynamic _, ms)) ->
                 JCode.OpInvoke (`Static JBasics.java_lang_object, ms)
             | opcode ->