parsetree.diff

 [
   structure_item (test.ml[1,0+0]..[4,53+17])
     Pstr_value Nonrec
     [
       <def>
         pattern (test.ml[1,0+4]..[1,0+5])
           Ppat_any
         expression (test.ml[2,8+2]..[4,53+17])
           Pexp_let Nonrec
           [
             <def>
-              pattern (test.ml[2,8+2]..[4,53+17])
-                Ppat_var "__ppx_lwt_0" (test.ml[2,8+2]..[4,53+17])
+              pattern (test.ml[2,8+14]..[2,8+26])
+                Ppat_var "__ppx_lwt_0" (test.ml[2,8+14]..[2,8+26])
               expression (test.ml[2,8+14]..[2,8+26])
                 Pexp_apply
                 expression (test.ml[2,8+14]..[2,8+24])
                   Pexp_ident "Lwt.return" (test.ml[2,8+14]..[2,8+24])
                 [
                   <arg>
                   Nolabel
                     expression (test.ml[2,8+25]..[2,8+26])
                       Pexp_constant PConst_int (5,None)
                 ]
           ]
           expression (test.ml[2,8+2]..[4,53+17])
             Pexp_apply
             expression (test.ml[2,8+2]..[4,53+17])
               Pexp_ident "Lwt.backtrace_bind" (test.ml[2,8+2]..[4,53+17])
             [
               <arg>
               Nolabel
                 expression (test.ml[2,8+2]..[4,53+17])
                   Pexp_fun
                   Nolabel
                   None
                   pattern (test.ml[2,8+2]..[4,53+17])
                     Ppat_var "exn" (test.ml[2,8+2]..[4,53+17])
                   expression (test.ml[2,8+2]..[4,53+17])
                     Pexp_try
                     expression (test.ml[2,8+2]..[4,53+17])
                       Pexp_apply
                       expression (test.ml[2,8+2]..[4,53+17])
                         Pexp_ident "raise" (test.ml[2,8+2]..[4,53+17])
                       [
                         <arg>
                         Nolabel
                           expression (test.ml[2,8+2]..[4,53+17])
                             Pexp_ident "exn" (test.ml[2,8+2]..[4,53+17])
                       ]
                     [
                       <case>
                         pattern (test.ml[2,8+2]..[4,53+17])
                           Ppat_var "exn" (test.ml[2,8+2]..[4,53+17])
                         expression (test.ml[2,8+2]..[4,53+17])
                           Pexp_ident "exn" (test.ml[2,8+2]..[4,53+17])
                     ]
               <arg>
               Nolabel
-                expression (test.ml[2,8+2]..[4,53+17])
-                  Pexp_ident "__ppx_lwt_0" (test.ml[2,8+2]..[4,53+17])
+                expression (test.ml[2,8+14]..[2,8+26])
+                  Pexp_ident "__ppx_lwt_0" (test.ml[2,8+14]..[2,8+26])
               <arg>
               Nolabel
-                expression (test.ml[2,8+2]..[2,8+26])
+                expression (test.ml[2,8+2]..[4,53+17])
                   Pexp_fun
                   Nolabel
                   None
                   pattern (test.ml[2,8+10]..[2,8+11])
                     Ppat_var "a" (test.ml[2,8+10]..[2,8+11])
                   expression (test.ml[3,38+2]..[4,53+17])
                     Pexp_let Nonrec
                     [
                       <def>
                         pattern (test.ml[3,38+6]..[3,38+7])
                           Ppat_var "b" (test.ml[3,38+6]..[3,38+7])
                         expression (test.ml[3,38+10]..[3,38+11])
                           Pexp_constant PConst_int (6,None)
                     ]
                     expression (test.ml[4,53+2]..[4,53+17])
                       Pexp_ident "Lwt.return_unit" (test.ml[4,53+2]..[4,53+17])
             ]
     ]
 ]