--- a/src/ppx/instrument.ml	2022-10-31 16:01:28.486756629 -0600

+++ b/src/ppx/instrument.ml	2022-10-31 17:05:13.572237694 -0600

@@ -1039,24 +1039,24 @@ class instrumenter =

   let instrument_cases = Generated_code.instrument_cases points in

   object (self)

-    inherit Ppxlib.Ast_traverse.map_with_expansion_context as super

+    inherit Ppxlib.Ast_traverse.map_with_expansion_context_and_errors as super

     method! class_expr ctxt ce =

       let loc = ce.pcl_loc in

       let attrs = ce.pcl_attributes in

-      let ce = super#class_expr ctxt ce in

+      let ce, locs = super#class_expr ctxt ce in

       match ce.pcl_desc with

       | Pcl_fun (l, e, p, ce) ->

-        Cl.fun_ ~loc ~attrs l (Option.map instrument_expr e) p ce

+        Cl.fun_ ~loc ~attrs l (Option.map instrument_expr e) p ce, locs

       | _ ->

-        ce

+        ce, locs

     method! class_field ctxt cf =

       let loc = cf.pcf_loc in

       let attrs = cf.pcf_attributes in

-      let cf = super#class_field ctxt cf in

+      let cf, locs = super#class_field ctxt cf in

       match cf.pcf_desc with

       | Pcf_method (name, private_, cf) ->

@@ -1065,13 +1065,13 @@ class instrumenter =

           (match cf with

           | Cfk_virtual _ -> cf

           | Cfk_concrete (o, e) ->

-            Cf.concrete o (instrument_expr e))

+            Cf.concrete o (instrument_expr e)), locs

       | Pcf_initializer e ->

-        Cf.initializer_ ~loc ~attrs (instrument_expr e)

+        Cf.initializer_ ~loc ~attrs (instrument_expr e), locs

       | _ ->

-        cf

+        cf, locs

     method! expression ctxt e =

       let is_trivial_function = Parsetree.(function

@@ -1494,17 +1494,19 @@ class instrumenter =

                 (f, traverse ~is_in_tail_position:false e)))

           | Pexp_letmodule (m, e, e') ->

+            let mexpr', _locs = (self#module_expr ctxt e) in

             Exp.letmodule ~loc ~attrs

               m

-              (self#module_expr ctxt e)

+              mexpr'

               (traverse ~is_in_tail_position e')

           | Pexp_letexception (c, e) ->

             Exp.letexception ~loc ~attrs c (traverse ~is_in_tail_position e)

           | Pexp_open (m, e) ->

+            let oexpr', _locs =  (self#open_declaration ctxt m) in

             Exp.open_ ~loc ~attrs

-              (self#open_declaration ctxt m)

+              oexpr'

               (traverse ~is_in_tail_position e)

           | Pexp_newtype (t, e) ->

@@ -1513,10 +1515,12 @@ class instrumenter =

           (* Expressions that don't need instrumentation, and where AST

              traversal leaves the expression language. *)

           | Pexp_object c ->

-            Exp.object_ ~loc ~attrs (self#class_structure ctxt c)

+            let cstr, _locs = (self#class_structure ctxt c) in

+            Exp.object_ ~loc ~attrs cstr

           | Pexp_pack m ->

-            Exp.pack ~loc ~attrs (self#module_expr ctxt m)

+            let mexpr', _locs = (self#module_expr ctxt m) in

+            Exp.pack ~loc ~attrs mexpr'

           (* Expressions that are not recursively traversed at all. *)

           | Pexp_extension _ | Pexp_unreachable ->

@@ -1536,7 +1540,7 @@ class instrumenter =

       in

-      traverse ~is_in_tail_position:false e

+      traverse ~is_in_tail_position:false e, []

     (* Set to [true] upon encountering [[@@@coverage.off]], and back to

        [false] again upon encountering [[@@@coverage.on]]. *)

@@ -1548,7 +1552,7 @@ class instrumenter =

       match si.pstr_desc with

       | Pstr_value (rec_flag, bindings) ->

         if structure_instrumentation_suppressed then

-          si

+          si, []

         else

           let bindings =

@@ -1580,16 +1584,18 @@ class instrumenter =

               if do_not_instrument then

                 binding

               else

-                {binding with pvb_expr = self#expression ctxt binding.pvb_expr}

+                let expr', _errs = self#expression ctxt binding.pvb_expr in

+                {binding with pvb_expr = expr'}

             end

           in

-          Str.value ~loc rec_flag bindings

+          Str.value ~loc rec_flag bindings, []

       | Pstr_eval (e, a) ->

         if structure_instrumentation_suppressed then

-          si

+          si, []

         else

-          Str.eval ~loc ~attrs:a (self#expression ctxt e)

+          let expr', errors = self#expression ctxt e in

+          Str.eval ~loc ~attrs:a expr', errors

       | Pstr_attribute attribute ->

         let kind = Coverage_attributes.recognize attribute in

@@ -1612,17 +1618,17 @@ class instrumenter =

           Location.raise_errorf

             ~loc:attribute.attr_loc "coverage exclude_file is not allowed here."

         end;

-        si

+        si, []

       | _ ->

         super#structure_item ctxt si

     (* Don't instrument payloads of extensions and attributes. *)

     method! extension _ e =

-      e

+      e, []

     method! attribute _ a =

-      a

+      a, []

     method! structure ctxt ast =

       let saved_structure_instrumentation_suppressed =

@@ -1655,7 +1661,7 @@ class instrumenter =

           ast

         else begin

-          let instrumented_ast = super#structure ctxt ast in

+          let instrumented_ast, _errs = super#structure ctxt ast in

           let runtime_initialization =

             Generated_code.runtime_initialization points path in

           runtime_initialization @ instrumented_ast

--- a/src/ppx/instrument.mli	2022-03-14 01:39:55.000000000 -0600

+++ b/src/ppx/instrument.mli	2022-10-31 15:48:11.733614835 -0600

@@ -5,7 +5,7 @@

 class instrumenter : object

-   inherit Ppxlib.Ast_traverse.map_with_expansion_context

+   inherit Ppxlib.Ast_traverse.map_with_expansion_context_and_errors

    method transform_impl_file:

       Ppxlib.Expansion_context.Base.t ->