diff --git a/infer/src/checkers/androidFramework.ml b/infer/src/absint/AndroidFramework.ml
similarity index 100%
rename from infer/src/checkers/androidFramework.ml
rename to infer/src/absint/AndroidFramework.ml
diff --git a/infer/src/checkers/androidFramework.mli b/infer/src/absint/AndroidFramework.mli
similarity index 100%
rename from infer/src/checkers/androidFramework.mli
rename to infer/src/absint/AndroidFramework.mli
diff --git a/infer/src/checkers/dataflow.ml b/infer/src/absint/DataFlow.ml
similarity index 96%
rename from infer/src/checkers/dataflow.ml
rename to infer/src/absint/DataFlow.ml
index 710e9dabc..471b5ed5b 100644
--- a/infer/src/checkers/dataflow.ml
+++ b/infer/src/absint/DataFlow.ml
@@ -166,9 +166,8 @@ end
 
 (* MakeDF *)
 
-(** Example dataflow callback: compute the the distance from a node to the start node. *)
-let _callback_test_dataflow {Callbacks.summary; _} =
-  let proc_desc = Summary.get_proc_desc summary in
+(** Example dataflow analysis: compute the the distance from a node to the start node. *)
+let _test_dataflow proc_desc =
   let verbose = false in
   let module DFCount = MakeDF (struct
     type t = int
@@ -189,5 +188,4 @@ let _callback_test_dataflow {Callbacks.summary; _} =
   let do_node node =
     match transitions node with DFCount.Transition _ -> () | DFCount.Dead_state -> ()
   in
-  List.iter ~f:do_node (Procdesc.get_nodes proc_desc) ;
-  summary
+  List.iter ~f:do_node (Procdesc.get_nodes proc_desc)
diff --git a/infer/src/checkers/dataflow.mli b/infer/src/absint/DataFlow.mli
similarity index 100%
rename from infer/src/checkers/dataflow.mli
rename to infer/src/absint/DataFlow.mli
diff --git a/infer/src/absint/Decompile.ml b/infer/src/absint/Decompile.ml
new file mode 100644
index 000000000..23e54427a
--- /dev/null
+++ b/infer/src/absint/Decompile.ml
@@ -0,0 +1,58 @@
+(*
+ * 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
+module L = Logging
+
+(** Find a boolean assignment to a temporary variable holding a boolean condition. The boolean
+    parameter indicates whether the true or false branch is required. *)
+let rec find_boolean_assignment node pvar true_branch : Procdesc.Node.t option =
+  let find_instr n =
+    let filter = function
+      | Sil.Store {e1= Exp.Lvar pvar_; e2= Exp.Const (Const.Cint i)} when Pvar.equal pvar pvar_ ->
+          Bool.(IntLit.iszero i <> true_branch)
+      | _ ->
+          false
+    in
+    Instrs.exists ~f:filter (Procdesc.Node.get_instrs n)
+  in
+  match Procdesc.Node.get_preds node with
+  | [pred_node] ->
+      find_boolean_assignment pred_node pvar true_branch
+  | [n1; n2] ->
+      if find_instr n1 then Some n1 else if find_instr n2 then Some n2 else None
+  | _ ->
+      None
+
+
+(** Find the function call instruction used to initialize normal variable [id], and return the
+    function name and arguments *)
+let find_normal_variable_funcall (node : Procdesc.Node.t) (id : Ident.t) :
+    (Exp.t * Exp.t list * Location.t * CallFlags.t) option =
+  let find_declaration _ = function
+    | Sil.Call ((id0, _), fun_exp, args, loc, call_flags) when Ident.equal id id0 ->
+        Some (fun_exp, List.map ~f:fst args, loc, call_flags)
+    | _ ->
+        None
+  in
+  let res = Procdesc.Node.find_in_node_or_preds node ~f:find_declaration in
+  if Config.trace_error && is_none res then
+    L.d_printfln "find_normal_variable_funcall could not find %a in node %a" Ident.pp id
+      Procdesc.Node.pp node ;
+  res
+
+
+(** Find a program variable assignment in the current node or predecessors. *)
+let find_program_variable_assignment node pvar : (Procdesc.Node.t * Ident.t) option =
+  let find_instr node = function
+    | Sil.Store {e1= Exp.Lvar pvar_; e2= Exp.Var id}
+      when Pvar.equal pvar pvar_ && Ident.is_normal id ->
+        Some (node, id)
+    | _ ->
+        None
+  in
+  Procdesc.Node.find_in_node_or_preds node ~f:find_instr
diff --git a/infer/src/absint/Decompile.mli b/infer/src/absint/Decompile.mli
new file mode 100644
index 000000000..9d75e8290
--- /dev/null
+++ b/infer/src/absint/Decompile.mli
@@ -0,0 +1,21 @@
+(*
+ * 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 find_boolean_assignment : Procdesc.Node.t -> Pvar.t -> bool -> Procdesc.Node.t option
+(** Find a boolean assignment to a temporary variable holding a boolean condition. The boolean
+    parameter indicates whether the true or false branch is required. *)
+
+val find_normal_variable_funcall :
+  Procdesc.Node.t -> Ident.t -> (Exp.t * Exp.t list * Location.t * CallFlags.t) option
+(** Find the function call instruction used to initialize normal variable [id], and return the
+    function name and arguments *)
+
+val find_program_variable_assignment :
+  Procdesc.Node.t -> Pvar.t -> (Procdesc.Node.t * Ident.t) option
+(** Find a program variable assignment in the current node or straightline predecessor. *)
diff --git a/infer/src/biabduction/errdesc.ml b/infer/src/biabduction/errdesc.ml
index b6e2fa1ae..a38f616e7 100644
--- a/infer/src/biabduction/errdesc.ml
+++ b/infer/src/biabduction/errdesc.ml
@@ -72,35 +72,6 @@ let explain_deallocate_constant_string s ra =
 
 let verbose = Config.trace_error
 
-(** Find the function call instruction used to initialize normal variable [id], and return the
-    function name and arguments *)
-let find_normal_variable_funcall (node : Procdesc.Node.t) (id : Ident.t) :
-    (Exp.t * Exp.t list * Location.t * CallFlags.t) option =
-  let find_declaration _ = function
-    | Sil.Call ((id0, _), fun_exp, args, loc, call_flags) when Ident.equal id id0 ->
-        Some (fun_exp, List.map ~f:fst args, loc, call_flags)
-    | _ ->
-        None
-  in
-  let res = Procdesc.Node.find_in_node_or_preds node ~f:find_declaration in
-  if verbose && is_none res then
-    L.d_printfln "find_normal_variable_funcall could not find %a in node %a" Ident.pp id
-      Procdesc.Node.pp node ;
-  res
-
-
-(** Find a program variable assignment in the current node or predecessors. *)
-let find_program_variable_assignment node pvar : (Procdesc.Node.t * Ident.t) option =
-  let find_instr node = function
-    | Sil.Store {e1= Exp.Lvar pvar_; e2= Exp.Var id}
-      when Pvar.equal pvar pvar_ && Ident.is_normal id ->
-        Some (node, id)
-    | _ ->
-        None
-  in
-  Procdesc.Node.find_in_node_or_preds node ~f:find_instr
-
-
 (** Special case for C++, where we translate code like [struct X; X getX() { X x; return X; }] as
     [void getX(struct X * frontend_generated_pvar)]. This lets us recognize that X was returned from
     getX *)
@@ -131,27 +102,6 @@ let find_ident_assignment node id : (Procdesc.Node.t * Exp.t) option =
   Procdesc.Node.find_in_node_or_preds node ~f:find_instr
 
 
-(** Find a boolean assignment to a temporary variable holding a boolean condition. The boolean
-    parameter indicates whether the true or false branch is required. *)
-let rec find_boolean_assignment node pvar true_branch : Procdesc.Node.t option =
-  let find_instr n =
-    let filter = function
-      | Sil.Store {e1= Exp.Lvar pvar_; e2= Exp.Const (Const.Cint i)} when Pvar.equal pvar pvar_ ->
-          Bool.(IntLit.iszero i <> true_branch)
-      | _ ->
-          false
-    in
-    Instrs.exists ~f:filter (Procdesc.Node.get_instrs n)
-  in
-  match Procdesc.Node.get_preds node with
-  | [pred_node] ->
-      find_boolean_assignment pred_node pvar true_branch
-  | [n1; n2] ->
-      if find_instr n1 then Some n1 else if find_instr n2 then Some n2 else None
-  | _ ->
-      None
-
-
 (** Find the Load instruction used to declare normal variable [id], and return the expression
     dereferenced to initialize [id] *)
 let rec find_normal_variable_load_ tenv (seen : Exp.Set.t) node id : DExp.t option =
@@ -243,7 +193,7 @@ and exp_lv_dexp_ tenv (seen_ : Exp.Set.t) node e : DExp.t option =
           Exp.d_exp e ;
           L.d_ln () ) ;
         if Pvar.is_frontend_tmp pvar then
-          match find_program_variable_assignment node pvar with
+          match Decompile.find_program_variable_assignment node pvar with
           | None -> (
             match find_struct_by_value_assignment node pvar with
             | Some (_, pname, loc, call_flags) ->
@@ -251,7 +201,7 @@ and exp_lv_dexp_ tenv (seen_ : Exp.Set.t) node e : DExp.t option =
             | None ->
                 None )
           | Some (node', id) -> (
-            match find_normal_variable_funcall node' id with
+            match Decompile.find_normal_variable_funcall node' id with
             | Some (fun_exp, eargs, loc, call_flags) ->
                 let fun_dexpo = exp_rv_dexp_ tenv seen node' fun_exp in
                 let blame_args = List.map ~f:(exp_rv_dexp_ tenv seen node') eargs in
diff --git a/infer/src/biabduction/errdesc.mli b/infer/src/biabduction/errdesc.mli
index fa394115a..7a6e7f388 100644
--- a/infer/src/biabduction/errdesc.mli
+++ b/infer/src/biabduction/errdesc.mli
@@ -17,22 +17,9 @@ val vpath_find : Tenv.t -> 'a Prop.t -> Exp.t -> DecompiledExp.vpath * Typ.t opt
 val hpred_is_open_resource : Tenv.t -> 'a Prop.t -> Predicates.hpred -> PredSymb.resource option
 (** Check whether the hpred is a |-> representing a resource in the Racquire state *)
 
-val find_normal_variable_funcall :
-  Procdesc.Node.t -> Ident.t -> (Exp.t * Exp.t list * Location.t * CallFlags.t) option
-(** Find the function call instruction used to initialize normal variable [id], and return the
-    function name and arguments *)
-
-val find_program_variable_assignment :
-  Procdesc.Node.t -> Pvar.t -> (Procdesc.Node.t * Ident.t) option
-(** Find a program variable assignment in the current node or straightline predecessor. *)
-
 val find_ident_assignment : Procdesc.Node.t -> Ident.t -> (Procdesc.Node.t * Exp.t) option
 (** Find a program variable assignment to id in the current node or predecessors. *)
 
-val find_boolean_assignment : Procdesc.Node.t -> Pvar.t -> bool -> Procdesc.Node.t option
-(** Find a boolean assignment to a temporary variable holding a boolean condition. The boolean
-    parameter indicates whether the true or false branch is required. *)
-
 val exp_rv_dexp : Tenv.t -> Procdesc.Node.t -> Exp.t -> DecompiledExp.t option
 (** describe rvalue [e] as a dexp *)
 
diff --git a/infer/src/deadcode/Makefile b/infer/src/deadcode/Makefile
index d43285bc0..0f23644bf 100644
--- a/infer/src/deadcode/Makefile
+++ b/infer/src/deadcode/Makefile
@@ -50,8 +50,8 @@ endif
 # Note that we run find under _build directory. Since we copy some
 # sources from subfolders to src/ folder to avoid duplicates we use
 # $(DEPTH_ONE) and iteration over main and library folders.
-LIBRARY_FOLDERS = . ./IR ./absint ./atd ./base ./biabduction ./c_stubs ./istd ./scripts
-INCLUDE_FOLDERS = -I absint -I IR -I atd -I base -I biabduction -I c_stubs -I istd -I scripts
+LIBRARY_FOLDERS = . ./IR ./absint ./atd ./base ./biabduction ./c_stubs ./istd ./nullsafe ./scripts
+INCLUDE_FOLDERS = -I absint -I IR -I atd -I base -I biabduction -I c_stubs -I istd -I nullsafe -I scripts
 
 ml_src_files:=$(shell \
 	cd $(INFER_BUILD_DIR); \
diff --git a/infer/src/dune.in b/infer/src/dune.in
index a6cdb9ce4..32af18cef 100644
--- a/infer/src/dune.in
+++ b/infer/src/dune.in
@@ -19,7 +19,6 @@ let source_dirs =
     ; "cost"
     ; "integration"
     ; "labs"
-    ; "nullsafe"
     ; "pulse"
     ; "quandary"
     ; "test_determinator"
@@ -57,6 +56,8 @@ let infer_cflags =
   ; "-open"
   ; "Biabduction"
   ; "-open"
+  ; "Nullsafe"
+  ; "-open"
   ; "Absint"
   ; "-open"
   ; "OpenSource"
@@ -89,7 +90,7 @@ let main_lib_stanza =
 |}
     infer_cflags
     (String.concat " "
-       ("biabduction" :: "absint" :: "InferCStubs" :: "InferIR" :: common_libraries))
+       ("biabduction" :: "nullsafe" :: "absint" :: "InferCStubs" :: "InferIR" :: common_libraries))
     (String.concat " " infer_binaries)
 
 
diff --git a/infer/src/checkers/idenv.ml b/infer/src/nullsafe/IDEnv.ml
similarity index 95%
rename from infer/src/checkers/idenv.ml
rename to infer/src/nullsafe/IDEnv.ml
index 0a8d1e56a..12450cf84 100644
--- a/infer/src/checkers/idenv.ml
+++ b/infer/src/nullsafe/IDEnv.ml
@@ -38,7 +38,7 @@ let expand_expr_temps idenv node exp_ =
   let exp = expand_expr idenv exp_ in
   match exp with
   | Exp.Lvar pvar when Pvar.is_frontend_tmp pvar -> (
-    match Errdesc.find_program_variable_assignment node pvar with
+    match Decompile.find_program_variable_assignment node pvar with
     | None ->
         exp
     | Some (_, id) ->
diff --git a/infer/src/checkers/idenv.mli b/infer/src/nullsafe/IDEnv.mli
similarity index 100%
rename from infer/src/checkers/idenv.mli
rename to infer/src/nullsafe/IDEnv.mli
diff --git a/infer/src/nullsafe/dune b/infer/src/nullsafe/dune
new file mode 100644
index 000000000..374a52c9d
--- /dev/null
+++ b/infer/src/nullsafe/dune
@@ -0,0 +1,14 @@
+; 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.
+
+(library
+ (name nullsafe)
+ (public_name infer.nullsafe)
+ (flags
+  (:standard -open Core -open InferIR -open InferStdlib -open IStd -open InferGenerated
+    -open InferBase -open Absint -open Biabduction))
+ (libraries core InferStdlib InferGenerated InferBase InferIR absint biabduction)
+ (preprocess (pps ppx_compare ppx_sexp_conv))
+)
diff --git a/infer/src/nullsafe/eradicate.ml b/infer/src/nullsafe/eradicate.ml
index ae69b455c..287771369 100644
--- a/infer/src/nullsafe/eradicate.ml
+++ b/infer/src/nullsafe/eradicate.ml
@@ -8,7 +8,6 @@
 open! IStd
 module L = Logging
 module F = Format
-open Dataflow
 
 let callback1 ({IntraproceduralAnalysis.proc_desc= curr_pdesc; _} as analysis_data)
     find_canonical_duplicate calls_this checks idenv annotated_signature linereader proc_loc :
@@ -66,7 +65,7 @@ let callback1 ({IntraproceduralAnalysis.proc_desc= curr_pdesc; _} as analysis_da
     let exit_node = Procdesc.get_exit_node curr_pdesc in
     check_return find_canonical_duplicate exit_node final_typestate annotated_signature proc_loc
   in
-  let module DFTypeCheck = MakeDF (struct
+  let module DFTypeCheck = DataFlow.MakeDF (struct
     type t = TypeState.t
 
     let equal = TypeState.equal
@@ -76,7 +75,7 @@ let callback1 ({IntraproceduralAnalysis.proc_desc= curr_pdesc; _} as analysis_da
     let pp_name fmt = F.pp_print_string fmt "eradicate"
 
     let do_node node typestate =
-      NodePrinter.with_session ~pp_name node ~f:(fun () ->
+      AnalysisCallbacks.html_debug_new_node_session ~pp_name node ~f:(fun () ->
           AnalysisState.set_node node ;
           if Config.write_html then L.d_printfln "before:@\n%a@\n" TypeState.pp typestate ;
           let {TypeCheck.normal_flow_typestate; exception_flow_typestates} =
@@ -89,7 +88,7 @@ let callback1 ({IntraproceduralAnalysis.proc_desc= curr_pdesc; _} as analysis_da
           (normal_flow_typestates, exception_flow_typestates) )
 
 
-    let proc_throws _ = DontKnow
+    let proc_throws _ = DataFlow.DontKnow
   end) in
   let initial_typestate = get_initial_typestate () in
   do_before_dataflow initial_typestate ;
@@ -104,7 +103,7 @@ let callback1 ({IntraproceduralAnalysis.proc_desc= curr_pdesc; _} as analysis_da
 
 let analyze_one_procedure ({IntraproceduralAnalysis.tenv; proc_desc; _} as analysis_data) calls_this
     checks annotated_signature linereader proc_loc : unit =
-  let idenv = Idenv.create proc_desc in
+  let idenv = IDEnv.create proc_desc in
   let find_duplicate_nodes = State.mk_find_duplicate_nodes proc_desc in
   let find_canonical_duplicate node =
     let duplicate_nodes = find_duplicate_nodes node in
@@ -131,7 +130,7 @@ let analyze_one_procedure ({IntraproceduralAnalysis.tenv; proc_desc; _} as analy
               (Procdesc.get_attributes pdesc)
           in
           let loc = Procdesc.get_loc pdesc in
-          (ann_sig, loc, Idenv.create pdesc)
+          (ann_sig, loc, IDEnv.create pdesc)
     in
     let checks', calls_this' =
       if do_checks then (checks, calls_this)
diff --git a/infer/src/nullsafe/eradicateChecks.ml b/infer/src/nullsafe/eradicateChecks.ml
index 6d4a414e4..c87ae5517 100644
--- a/infer/src/nullsafe/eradicateChecks.ml
+++ b/infer/src/nullsafe/eradicateChecks.ml
@@ -87,7 +87,7 @@ let check_condition_for_redundancy
     | None ->
         false
   in
-  let is_temp = Idenv.exp_is_temp idenv expr in
+  let is_temp = IDEnv.exp_is_temp idenv expr in
   let should_report =
     (* NOTE: We have different levels of non-nullability. In practice there is a big difference
        between certainty for different cases: whether expression is the result of something that can not be null
diff --git a/infer/src/nullsafe/typeCheck.ml b/infer/src/nullsafe/typeCheck.ml
index 656c021f3..b7c39e73d 100644
--- a/infer/src/nullsafe/typeCheck.ml
+++ b/infer/src/nullsafe/typeCheck.ml
@@ -206,7 +206,7 @@ let handle_field_access_via_temporary idenv curr_pname typestate exp =
         None
   in
   let handle_temporary e =
-    match Idenv.expand_expr idenv e with
+    match IDEnv.expand_expr idenv e with
     | Exp.Lvar pvar when name_is_temporary (Pvar.to_string pvar) -> (
       match pvar_get_origin pvar with
       | Some TypeOrigin.This ->
@@ -230,7 +230,7 @@ let handle_field_access_via_temporary idenv curr_pname typestate exp =
 (* Try to convert a function call to a pvar that originated it; fallback to an original expression in case of failure *)
 let funcall_exp_to_original_pvar_exp tenv curr_pname typestate exp ~is_assignment ~call_node ~node
     id =
-  match Errdesc.find_normal_variable_funcall call_node id with
+  match Decompile.find_normal_variable_funcall call_node id with
   | Some (Exp.Const (Const.Cfun pn), _, _, _)
     when not (ComplexExpressions.procname_used_in_condition pn) -> (
     match ComplexExpressions.exp_to_string tenv node exp with
@@ -276,17 +276,17 @@ let convert_complex_exp_to_pvar_and_register_field_in_typestate tenv idenv curr_
       F.fprintf f "Exp: %a;@\nTypestate: @\n%a" Exp.pp exp TypeState.pp typestate )
     (fun () ->
       let exp =
-        handle_field_access_via_temporary idenv curr_pname typestate (Idenv.expand_expr idenv exp_)
+        handle_field_access_via_temporary idenv curr_pname typestate (IDEnv.expand_expr idenv exp_)
       in
       let default = (exp, typestate) in
       match exp with
-      | Exp.Var id when Option.is_some (Errdesc.find_normal_variable_funcall node id) ->
+      | Exp.Var id when Option.is_some (Decompile.find_normal_variable_funcall node id) ->
           ( funcall_exp_to_original_pvar_exp tenv curr_pname typestate exp ~is_assignment
               ~call_node:node ~node id
           , typestate )
       | Exp.Lvar pvar when Pvar.is_frontend_tmp pvar -> (
           let frontend_variable_assignment =
-            Errdesc.find_program_variable_assignment original_node pvar
+            Decompile.find_program_variable_assignment original_node pvar
           in
           match frontend_variable_assignment with
           | Some (call_node, id) ->
@@ -310,7 +310,7 @@ let convert_complex_exp_to_pvar_and_register_field_in_typestate tenv idenv curr_
                  ~f:(fun (_, nullability) -> InferredNullability.get_origin nullability)
                  ~default:TypeOrigin.OptimisticFallback
           in
-          let exp' = Idenv.expand_expr_temps idenv original_node exp_ in
+          let exp' = IDEnv.expand_expr_temps idenv original_node exp_ in
           let is_parameter_field pvar =
             (* parameter.field *)
             let name = Pvar.get_name pvar in
@@ -440,7 +440,7 @@ let pvar_apply instr_ref idenv tenv curr_pname curr_annotated_signature loc hand
       let typestate' = handle_pvar typestate pvar in
       let curr_node = TypeErr.InstrRef.get_node instr_ref in
       let frontent_variable_assignment =
-        if Pvar.is_frontend_tmp pvar then Errdesc.find_program_variable_assignment curr_node pvar
+        if Pvar.is_frontend_tmp pvar then Decompile.find_program_variable_assignment curr_node pvar
         else None
       in
       match frontent_variable_assignment with
@@ -448,7 +448,7 @@ let pvar_apply instr_ref idenv tenv curr_pname curr_annotated_signature loc hand
           typestate'
       | Some (node', id) -> (
           (* handle the case where pvar is a frontend-generated program variable *)
-          let exp = Idenv.expand_expr idenv (Exp.Var id) in
+          let exp = IDEnv.expand_expr idenv (Exp.Var id) in
           match
             convert_complex_exp_to_pvar ~is_assignment:false tenv idenv curr_pname
               curr_annotated_signature ~node:node' ~original_node:node exp typestate' loc
@@ -481,7 +481,7 @@ let typecheck_expr_for_errors analysis_data ~nullsafe_mode find_canonical_duplic
 let java_get_vararg_values node pvar idenv =
   let values_of_instr acc = function
     | Sil.Store {e1= Exp.Lindex (array_exp, _); e2= content_exp}
-      when Exp.equal (Exp.Lvar pvar) (Idenv.expand_expr idenv array_exp) ->
+      when Exp.equal (Exp.Lvar pvar) (IDEnv.expand_expr idenv array_exp) ->
         (* Each vararg argument is an assignment to a pvar denoting an array of objects. *)
         content_exp :: acc
     | _ ->
@@ -490,7 +490,7 @@ let java_get_vararg_values node pvar idenv =
   let values_of_node acc n =
     Procdesc.Node.get_instrs n |> Instrs.fold ~f:values_of_instr ~init:acc
   in
-  match Errdesc.find_program_variable_assignment node pvar with
+  match Decompile.find_program_variable_assignment node pvar with
   | Some (node', _) ->
       Procdesc.fold_slope_range node' node ~f:values_of_node ~init:[]
   | None ->
@@ -543,7 +543,7 @@ let do_preconditions_check_not_null
       let curr_pname = Procdesc.get_proc_name curr_pdesc in
       if is_vararg then
         let do_vararg_value e ts =
-          match Idenv.expand_expr idenv e with
+          match IDEnv.expand_expr idenv e with
           | Exp.Lvar pvar1 ->
               pvar_apply instr_ref idenv tenv curr_pname curr_annotated_signature loc
                 (clear_nullable_flag
@@ -588,7 +588,7 @@ let do_preconditions_check_state instr_ref idenv tenv curr_pname curr_annotated_
   let handle_negated_condition cond_node =
     let do_instr instr =
       let set_flag expression =
-        let cond_e = Idenv.expand_expr_temps idenv cond_node expression in
+        let cond_e = IDEnv.expand_expr_temps idenv cond_node expression in
         match
           convert_complex_exp_to_pvar ~is_assignment:false tenv idenv curr_pname
             curr_annotated_signature ~node:cond_node ~original_node:node cond_e typestate' loc
@@ -615,7 +615,7 @@ let do_preconditions_check_state instr_ref idenv tenv curr_pname curr_annotated_
       (* temporary variable for the value of the boolean condition *)
       let curr_node = TypeErr.InstrRef.get_node instr_ref in
       let branch = false in
-      match Errdesc.find_boolean_assignment curr_node pvar branch with
+      match Decompile.find_boolean_assignment curr_node pvar branch with
       (* In foo(cond1 && cond2), the node that sets the result to false
          has all the negated conditions as parents. *)
       | Some boolean_assignment_node ->
@@ -680,7 +680,7 @@ let handle_assignment_in_condition_for_sil_prune idenv node pvar =
       let found = ref None in
       let do_instr i =
         match i with
-        | Sil.Store {e1= e; e2= e'} when Exp.equal (Exp.Lvar pvar) (Idenv.expand_expr idenv e') ->
+        | Sil.Store {e1= e; e2= e'} when Exp.equal (Exp.Lvar pvar) (IDEnv.expand_expr idenv e') ->
             found := Some e
         | _ ->
             ()
@@ -701,13 +701,13 @@ let rec normalize_cond_for_sil_prune_rec idenv ~node ~original_node cond =
       let node'', c2' = normalize_cond_for_sil_prune_rec idenv ~node:node' ~original_node c2 in
       (node'', Exp.BinOp (bop, c1', c2'))
   | Exp.Var _ ->
-      let c' = Idenv.expand_expr idenv cond in
+      let c' = IDEnv.expand_expr idenv cond in
       if not (Exp.equal c' cond) then normalize_cond_for_sil_prune_rec idenv ~node ~original_node c'
       else (node, c')
   | Exp.Lvar pvar when Pvar.is_frontend_tmp pvar -> (
     match handle_assignment_in_condition_for_sil_prune idenv original_node pvar with
     | None -> (
-      match Errdesc.find_program_variable_assignment node pvar with
+      match Decompile.find_program_variable_assignment node pvar with
       | Some (node', id) ->
           (node', Exp.Var id)
       | None ->
@@ -732,7 +732,7 @@ let rec check_condition_for_sil_prune
   let extract_arguments_from_call filter_callee expr =
     match expr with
     | Exp.Var id -> (
-      match Errdesc.find_normal_variable_funcall node id with
+      match Decompile.find_normal_variable_funcall node id with
       | Some (Exp.Const (Const.Cfun pn), arguments, _, _) when filter_callee pn ->
           Some arguments
       | _ ->
diff --git a/infer/src/nullsafe/typeCheck.mli b/infer/src/nullsafe/typeCheck.mli
index 44ff8ba97..f1f00a04f 100644
--- a/infer/src/nullsafe/typeCheck.mli
+++ b/infer/src/nullsafe/typeCheck.mli
@@ -29,7 +29,7 @@ val typecheck_node :
      IntraproceduralAnalysis.t
   -> bool ref
   -> checks
-  -> Idenv.t
+  -> IDEnv.t
   -> find_canonical_duplicate
   -> AnnotatedSignature.t
   -> TypeState.t