From 8384e3d1f76c872a9242879a47abbdca9b469193 Mon Sep 17 00:00:00 2001
From: Christian Rinderknecht <Christian.Rinderknecht@tezcore.com>
Date: Mon, 20 Jan 2020 10:57:07 +0100
Subject: [PATCH] [WIP] Refactoring of front-end.

---
 src/passes/1-parser/cameligo/AST.ml        |   4 +-
 src/passes/1-parser/pascaligo.ml           | 296 ++++++++++++---------
 src/passes/1-parser/pascaligo/.links       |   2 +
 src/passes/1-parser/pascaligo/AST.ml       |  14 +-
 src/passes/1-parser/pascaligo/LexToken.mli |   9 +-
 src/passes/1-parser/pascaligo/LexToken.mll |  24 +-
 src/passes/1-parser/pascaligo/LexerMain.ml |   5 +
 src/passes/1-parser/pascaligo/ParToken.mly |   1 +
 src/passes/1-parser/pascaligo/Parser.mly   |  96 ++++---
 src/passes/1-parser/pascaligo/ParserLog.ml |  54 ++--
 src/passes/1-parser/pascaligo/Scoping.mli  |   1 +
 src/passes/1-parser/shared/EvalOpt.ml      |   6 +-
 src/passes/1-parser/shared/Lexer.mli       |   3 +-
 src/passes/1-parser/shared/Lexer.mll       |  81 +++---
 src/passes/1-parser/shared/LexerLog.ml     |  33 ++-
 src/passes/1-parser/shared/LexerLog.mli    |   3 +-
 src/passes/1-parser/shared/LexerUnit.ml    |  83 ++++--
 src/passes/1-parser/shared/LexerUnit.mli   |  13 +
 src/passes/1-parser/shared/Memo.ml         | 163 ++++++++++++
 src/passes/1-parser/shared/Memo.mli        | 120 +++++++++
 src/passes/1-parser/shared/ParserAPI.ml    |  32 +--
 src/passes/1-parser/shared/ParserAPI.mli   |  39 ++-
 src/passes/1-parser/shared/ParserUnit.ml   |  65 ++---
 src/passes/1-parser/shared/ParserUnit.mli  |   3 -
 vendors/ligo-utils/simple-utils/pos.ml     |  58 ++--
 vendors/ligo-utils/simple-utils/pos.mli    |  52 ++--
 vendors/ligo-utils/simple-utils/region.ml  |   4 +-
 vendors/ligo-utils/simple-utils/region.mli |   8 +-
 28 files changed, 855 insertions(+), 417 deletions(-)
 create mode 100644 src/passes/1-parser/shared/LexerUnit.mli
 create mode 100644 src/passes/1-parser/shared/Memo.ml
 create mode 100644 src/passes/1-parser/shared/Memo.mli

diff --git a/src/passes/1-parser/cameligo/AST.ml b/src/passes/1-parser/cameligo/AST.ml
index 25104af3e..b8ac37bd2 100644
--- a/src/passes/1-parser/cameligo/AST.ml
+++ b/src/passes/1-parser/cameligo/AST.ml
@@ -312,6 +312,7 @@ and comp_expr =
 | Neq   of neq   bin_op reg
 
 and record = field_assign reg ne_injection
+
 and projection = {
   struct_name : variable;
   selector    : dot;
@@ -335,6 +336,7 @@ and update = {
   updates : record reg;
   rbrace : rbrace;
 }
+
 and path =
   Name of variable
 | Path of projection reg
@@ -376,7 +378,7 @@ and cond_expr = {
   ifso     : expr;
   kwd_else : kwd_else;
   ifnot    : expr
-  }
+}
 
 (* Projecting regions from some nodes of the AST *)
 
diff --git a/src/passes/1-parser/pascaligo.ml b/src/passes/1-parser/pascaligo.ml
index 64c169f06..343f9195d 100644
--- a/src/passes/1-parser/pascaligo.ml
+++ b/src/passes/1-parser/pascaligo.ml
@@ -1,129 +1,148 @@
 open Trace
 
-module Parser = Parser_pascaligo.Parser
-module AST = Parser_pascaligo.AST
+(*module Parser = Parser_pascaligo.Parser*)
 (*module ParserLog = Parser_pascaligo.ParserLog*)
+module AST = Parser_pascaligo.AST
+module ParErr = Parser_pascaligo.ParErr
 module LexToken = Parser_pascaligo.LexToken
 module Lexer = Lexer.Make(LexToken)
 module Scoping = Parser_pascaligo.Scoping
+module SSet = Utils.String.Set
 
-module Errors = struct
+(* Mock options. TODO: Plug in cmdliner. *)
 
-  let lexer_error (e: Lexer.error AST.reg) =
-    let title () = "lexer error" in
-    let message () = Lexer.error_to_string e.value in
-    let data = [
-      ("parser_loc",
-       fun () -> Format.asprintf "%a" Location.pp_lift @@ e.region
-      )
-    ] in
-    error ~data title message
+let pre_options =
+  EvalOpt.make
+    ~libs:[]
+    ~verbose:SSet.empty
+    ~offsets:true
+    ~mode:`Point
+    ~cmd:EvalOpt.Quiet
+    ~mono:true (* Monolithic API of Menhir for now *)
+(*  ~input:None *)
+(*  ~expr:true  *)
 
-  let reserved_name Region.{value; region} =
-    let title () = Printf.sprintf "reserved name \"%s\"" value in
-    let message () = "" in
-    let data = [
+module Parser =
+  struct
+    type ast  = AST.t
+    type expr = AST.expr
+    include Parser_pascaligo.Parser
+  end
+
+module ParserLog =
+  struct
+    type ast  = AST.t
+    type expr = AST.expr
+    include Parser_pascaligo.ParserLog
+  end
+
+module PreUnit = ParserUnit.Make (Lexer)(AST)(Parser)(ParErr)(ParserLog)
+module Front   = ParserAPI.Make (Lexer)(Parser)(ParErr)
+
+let issue_error point =
+  let error = Front.format_error ~offsets:true (* TODO: CLI *)
+                                 `Point (* TODO: CLI *) point
+  in Stdlib.Error error
+
+module Errors =
+  struct
+    let reserved_name Region.{value; region} =
+      let title () = Printf.sprintf "reserved name \"%s\"" value in
+      let message () = "" in
+      let data = [
+          ("location",
+           fun () -> Format.asprintf "%a" Location.pp_lift @@ region)]
+      in error ~data title message
+
+    let non_linear_pattern Region.{value; region} =
+      let title () =
+        Printf.sprintf "repeated variable \"%s\" in this pattern" value in
+      let message () = "" in
+      let data = [
+          ("location",
+           fun () -> Format.asprintf "%a" Location.pp_lift @@ region)]
+      in error ~data title message
+
+    let duplicate_parameter Region.{value; region} =
+      let title () =
+        Printf.sprintf "duplicate parameter \"%s\"" value in
+      let message () = "" in
+      let data = [
+          ("location",
+           fun () -> Format.asprintf "%a" Location.pp_lift @@ region)]
+      in error ~data title message
+
+    let duplicate_variant Region.{value; region} =
+      let title () =
+        Printf.sprintf "duplicate variant \"%s\" in this\
+                        type declaration" value in
+      let message () = "" in
+      let data = [
+          ("location",
+           fun () -> Format.asprintf "%a" Location.pp_lift @@ region)]
+      in error ~data title message
+
+    let unrecognized_error source (start: Lexing.position)
+                           (stop: Lexing.position) lexbuf =
+      let title () = "unrecognized error" in
+      let file =
+        if source = "" then ""
+        else
+          Format.sprintf "In file \"%s|%s\"" start.pos_fname source in
+      let message () =
+        Format.sprintf
+                  "Parse error at \"%s\" from (%d, %d) to (%d, %d). %s\n"
+                  (Lexing.lexeme lexbuf)
+                  start.pos_lnum (start.pos_cnum - start.pos_bol)
+                  stop.pos_lnum (stop.pos_cnum - stop.pos_bol)
+                  file in
+      let loc = Region.make ~start:(Pos.from_byte start)
+                            ~stop:(Pos.from_byte stop) in
+      let data = [
+        ("unrecognized_loc",
+         fun () -> Format.asprintf "%a" Location.pp_lift @@ loc)]
+      in error ~data title message
+
+    let detached_attributes (attrs: AST.attributes) =
+      let title () = "detached attributes" in
+      let message () = "" in
+      let data = [
       ("location",
-       fun () -> Format.asprintf "%a" Location.pp_lift @@ region)
-    ] in
-    error ~data title message
+       fun () -> Format.asprintf "%a" Location.pp_lift @@ attrs.region)]
+      in error ~data title message
 
-  let non_linear_pattern Region.{value; region} =
-    let title () = Printf.sprintf "repeated variable \"%s\" in this pattern" value in
-    let message () = "" in
-    let data = [
-      ("location",
-       fun () -> Format.asprintf "%a" Location.pp_lift @@ region)
-    ] in
-    error ~data title message
-
-  let duplicate_parameter Region.{value; region} =
-    let title () = Printf.sprintf "duplicate parameter \"%s\"" value in
-    let message () = "" in
-    let data = [
-      ("location",
-       fun () -> Format.asprintf "%a" Location.pp_lift @@ region)
-    ] in
-    error ~data title message
-
-  let duplicate_variant Region.{value; region} =
-    let title () = Printf.sprintf "duplicate variant \"%s\" in this\
-                                   type declaration" value in
-    let message () = "" in
-    let data = [
-      ("location",
-       fun () -> Format.asprintf "%a" Location.pp_lift @@ region)
-    ] in
-    error ~data title message
-
-  let detached_attributes (attrs: AST.attributes) = 
-    let title () = "detached attributes" in 
-    let message () = "" in
-    let data = [
-      ("location",
-       fun () -> Format.asprintf "%a" Location.pp_lift @@ attrs.region)
-    ] in
-    error ~data title message
-
-  let parser_error source (start: Lexing.position) (end_: Lexing.position) lexbuf =
-    let title () = "parser error" in
-    let file = if source = "" then
-        ""
-      else
-        Format.sprintf "In file \"%s|%s\"" start.pos_fname source
-    in
-    let str = Format.sprintf
-              "Parse error at \"%s\" from (%d, %d) to (%d, %d). %s\n"
-              (Lexing.lexeme lexbuf)
-              start.pos_lnum (start.pos_cnum - start.pos_bol)
-              end_.pos_lnum (end_.pos_cnum - end_.pos_bol)
-              file
-    in
-    let message () = str in
-    let loc = if start.pos_cnum = -1 then
-      Region.make
-        ~start: Pos.min
-        ~stop:(Pos.from_byte end_)
-    else
-      Region.make
-        ~start:(Pos.from_byte start)
-        ~stop:(Pos.from_byte end_)
-    in
-    let data =
-      [
-        ("parser_loc",
-          fun () -> Format.asprintf "%a" Location.pp_lift @@ loc
-        )
-      ]
-    in
-    error ~data title message
-
-  let unrecognized_error source (start: Lexing.position) (end_: Lexing.position) lexbuf =
-    let title () = "unrecognized error" in
-    let file = if source = "" then
-        ""
-      else
-        Format.sprintf "In file \"%s|%s\"" start.pos_fname source
-    in
-    let str = Format.sprintf
-              "Parse error at \"%s\" from (%d, %d) to (%d, %d). %s\n"
-              (Lexing.lexeme lexbuf)
-              start.pos_lnum (start.pos_cnum - start.pos_bol)
-              end_.pos_lnum (end_.pos_cnum - end_.pos_bol)
-              file
-    in
-    let message () = str in
-    let loc = Region.make
-      ~start:(Pos.from_byte start)
-      ~stop:(Pos.from_byte end_)
-    in
-    let data = [
-      ("unrecognized_loc",
-        fun () -> Format.asprintf "%a" Location.pp_lift @@ loc
-      )
-    ] in
-    error ~data title message
+    let parser_error source (start: Lexing.position)
+                     (stop: Lexing.position) lexbuf =
+      let title () = "parser error" in
+      let file =
+        if source = "" then ""
+        else
+          Format.sprintf "In file \"%s|%s\"" start.pos_fname source in
+      let message () =
+        Format.sprintf
+          "Parse error at \"%s\" from (%d, %d) to (%d, %d). %s\n"
+          (Lexing.lexeme lexbuf)
+          start.pos_lnum (start.pos_cnum - start.pos_bol)
+          stop.pos_lnum (stop.pos_cnum - stop.pos_bol)
+          file in
+      let loc =
+        if start.pos_cnum = -1 then
+          Region.make ~start: Pos.min ~stop:(Pos.from_byte stop)
+        else
+          Region.make ~start:(Pos.from_byte start)
+                      ~stop:(Pos.from_byte stop) in
+      let data =
+        [("parser_loc",
+          fun () -> Format.asprintf "%a" Location.pp_lift @@ loc)] in
+      error ~data title message
 
+    let lexer_error (e: Lexer.error AST.reg) =
+      let title () = "lexer error" in
+      let message () = Lexer.error_to_string e.value in
+      let data = [
+          ("parser_loc",
+           fun () -> Format.asprintf "%a" Location.pp_lift @@ e.region)]
+      in error ~data title message
 end
 
 open Errors
@@ -131,35 +150,37 @@ open Errors
 type 'a parser = (Lexing.lexbuf -> LexToken.token) -> Lexing.lexbuf -> 'a
 
 let parse (parser: 'a parser) source lexbuf =
-  let Lexer.{read ; close ; _} = Lexer.open_token_stream None in
+  let Lexer.{read; close; _} = Lexer.open_token_stream None in
   let result =
-    try
-      ok (parser read lexbuf)
-    with
-      Scoping.Error (Scoping.Non_linear_pattern var) ->
-        fail @@ (non_linear_pattern var)
+    try ok (parser read lexbuf) with
+      Lexer.Error e ->
+        fail @@ lexer_error e
+    | Parser.Error ->
+        let start = Lexing.lexeme_start_p lexbuf in
+        let stop = Lexing.lexeme_end_p lexbuf in
+        fail @@ parser_error source start stop lexbuf
+    | Scoping.Error (Scoping.Non_linear_pattern var) ->
+        fail @@ non_linear_pattern var
     | Scoping.Error (Duplicate_parameter name) ->
-        fail @@ (duplicate_parameter name)
+        fail @@ duplicate_parameter name
     | Scoping.Error (Duplicate_variant name) ->
-        fail @@ (duplicate_variant name)
+        fail @@ duplicate_variant name
     | Scoping.Error (Reserved_name name) ->
-        fail @@ (reserved_name name)
-    | SyntaxError.Error (Detached_attributes attrs) ->
-        fail @@ (detached_attributes attrs)
+        fail @@ reserved_name name
+    | Scoping.Error (Detached_attributes attrs) ->
+        fail @@ detached_attributes attrs
     | Parser.Error ->
         let start = Lexing.lexeme_start_p lexbuf in
         let end_ = Lexing.lexeme_end_p lexbuf in
         fail @@ (parser_error source start end_ lexbuf)
     | Lexer.Error e ->
-        fail @@ (lexer_error e)
+        fail @@ lexer_error e
     | _ ->
-        let _ = Printexc.print_backtrace Pervasives.stdout in
+        let () = Printexc.print_backtrace Pervasives.stdout in
         let start = Lexing.lexeme_start_p lexbuf in
-        let end_ = Lexing.lexeme_end_p lexbuf in
-        fail @@ (unrecognized_error source start end_ lexbuf)
-  in
-  close ();
-  result
+        let stop = Lexing.lexeme_end_p lexbuf in
+        fail @@ unrecognized_error source start stop lexbuf
+  in close (); result
 
 let parse_file (source: string) : AST.t result =
   let pp_input =
@@ -177,6 +198,17 @@ let parse_file (source: string) : AST.t result =
   let lexbuf = Lexing.from_channel channel in
   parse (Parser.contract) source lexbuf
 
+let parse_file' (source: string) : AST.t result =
+  let module IO =
+    struct
+      let ext = "ligo"
+      let options = pre_options ~input:(Some source) ~expr:false
+    end in
+  let module Unit = PreUnit(IO) in
+  match Unit.parse Unit.parse_contract with
+    Ok ast -> ok ast
+  | Error error -> failwith "TODO" (* fail @@ parser_or_lexer_error error *)
+
 let parse_string (s:string) : AST.t result =
   let lexbuf = Lexing.from_string s in
   parse (Parser.contract) "" lexbuf
diff --git a/src/passes/1-parser/pascaligo/.links b/src/passes/1-parser/pascaligo/.links
index 8d77d2246..6cc2d4c32 100644
--- a/src/passes/1-parser/pascaligo/.links
+++ b/src/passes/1-parser/pascaligo/.links
@@ -20,4 +20,6 @@ $HOME/git/ligo/vendors/ligo-utils/simple-utils/region.ml
 ../shared/LexerUnit.ml
 ../shared/ParserUnit.mli
 ../shared/ParserUnit.ml
+../shared/Memo.mli
+../shared/Memo.ml
 Stubs/Simple_utils.ml
diff --git a/src/passes/1-parser/pascaligo/AST.ml b/src/passes/1-parser/pascaligo/AST.ml
index a855ea46e..ff00926d7 100644
--- a/src/passes/1-parser/pascaligo/AST.ml
+++ b/src/passes/1-parser/pascaligo/AST.ml
@@ -25,6 +25,7 @@ type 'a reg = 'a Region.reg
 
 type keyword        = Region.t
 type kwd_and        = Region.t
+type kwd_attributes = Region.t
 type kwd_begin      = Region.t
 type kwd_block      = Region.t
 type kwd_case       = Region.t
@@ -109,7 +110,7 @@ type field_name = string reg
 type map_name   = string reg
 type set_name   = string reg
 type constr     = string reg
-type attribute   = string reg
+type attribute  = string reg
 
 (* Parentheses *)
 
@@ -144,12 +145,12 @@ type t = {
 
 and ast = t
 
-and attributes = attribute list reg
+and attributes = attribute ne_injection reg
 
 and declaration =
-  TypeDecl  of type_decl reg
+  TypeDecl  of type_decl  reg
 | ConstDecl of const_decl reg
-| FunDecl   of fun_decl reg
+| FunDecl   of fun_decl   reg
 
 and const_decl = {
   kwd_const  : kwd_const;
@@ -159,7 +160,7 @@ and const_decl = {
   equal      : equal;
   init       : expr;
   terminator : semi option;
-  attributes : attributes;
+  attributes : attributes option
 }
 
 (* Type declarations *)
@@ -217,7 +218,7 @@ and fun_decl = {
   block_with   : (block reg * kwd_with) option;
   return       : expr;
   terminator   : semi option;
-  attributes   : attributes;
+  attributes   : attributes option;
 }
 
 and parameters = (param_decl, semi) nsepseq par reg
@@ -562,6 +563,7 @@ and field_assign = {
   equal      : equal;
   field_expr : expr
 }
+
 and record = field_assign reg ne_injection
 
 and projection = {
diff --git a/src/passes/1-parser/pascaligo/LexToken.mli b/src/passes/1-parser/pascaligo/LexToken.mli
index 598b6de4f..f2ce709ae 100644
--- a/src/passes/1-parser/pascaligo/LexToken.mli
+++ b/src/passes/1-parser/pascaligo/LexToken.mli
@@ -28,6 +28,11 @@ type lexeme = string
 
 (* TOKENS *)
 
+type attribute = {
+  header : string;
+  string : lexeme Region.reg
+}
+
 type t =
   (* Literals *)
 
@@ -38,6 +43,7 @@ type t =
 | Mutez  of (lexeme * Z.t) Region.reg
 | Ident  of lexeme Region.reg
 | Constr of lexeme Region.reg
+| Attr   of attribute
 
   (* Symbols *)
 
@@ -151,8 +157,7 @@ val mk_kwd    : lexeme -> Region.t -> (token,   kwd_err) result
 val mk_string : lexeme -> Region.t -> token
 val mk_bytes  : lexeme -> Region.t -> token
 val mk_constr : lexeme -> Region.t -> token
-val mk_attr   : lexeme -> Region.t -> (token,  attr_err) result
-val mk_attr2  : lexeme -> Region.t -> (token,  attr_err) result
+val mk_attr   : string -> lexeme -> Region.t -> (token, attr_err) result
 val eof       : Region.t -> token
 
 (* Predicates *)
diff --git a/src/passes/1-parser/pascaligo/LexToken.mll b/src/passes/1-parser/pascaligo/LexToken.mll
index 5a1e47c76..5a7020105 100644
--- a/src/passes/1-parser/pascaligo/LexToken.mll
+++ b/src/passes/1-parser/pascaligo/LexToken.mll
@@ -26,6 +26,11 @@ let rollback buffer =
 
 (* TOKENS *)
 
+type attribute = {
+  header : string;
+  string : lexeme Region.reg
+}
+
 type t =
   (* Literals *)
 
@@ -33,9 +38,10 @@ type t =
 | Bytes  of (lexeme * Hex.t) Region.reg
 | Int    of (lexeme * Z.t) Region.reg
 | Nat    of (lexeme * Z.t) Region.reg
-| Mutez    of (lexeme * Z.t) Region.reg
+| Mutez  of (lexeme * Z.t) Region.reg
 | Ident  of lexeme Region.reg
 | Constr of lexeme Region.reg
+| Attr   of attribute
 
   (* Symbols *)
 
@@ -144,6 +150,9 @@ let proj_token = function
 | Constr Region.{region; value} ->
     region, sprintf "Constr \"%s\"" value
 
+| Attr {header; string={region; value}} ->
+    region, sprintf "Attr (\"%s\",\"%s\")" header value
+
   (* Symbols *)
 
 | SEMI     region -> region, "SEMI"
@@ -217,7 +226,7 @@ let proj_token = function
 
 | C_None  region -> region, "C_None"
 | C_Some  region -> region, "C_Some"
-  
+
   (* Virtual tokens *)
 
 | EOF region -> region, "EOF"
@@ -233,6 +242,7 @@ let to_lexeme = function
 | Mutez i     -> fst i.Region.value
 | Ident id
 | Constr id -> id.Region.value
+| Attr {string; _} -> string.Region.value
 
   (* Symbols *)
 
@@ -312,6 +322,7 @@ let to_lexeme = function
 
 | EOF _ -> ""
 
+(* CONVERSIONS *)
 
 let to_string token ?(offsets=true) mode =
   let region, val_str = proj_token token in
@@ -365,7 +376,7 @@ let keywords = [
 
 let reserved =
   let open SSet in
-  empty |> add "args"
+  empty |> add "arguments"
 
 let constructors = [
   (fun reg -> False  reg);
@@ -489,8 +500,6 @@ let eof region = EOF region
 
 type sym_err = Invalid_symbol
 
-type attr_err = Invalid_attribute
-
 let mk_sym lexeme region =
   match lexeme with
   (* Lexemes in common with all concrete syntaxes *)
@@ -539,10 +548,9 @@ let mk_constr lexeme region =
 
 (* Attributes *)
 
-let mk_attr _lexeme _region = 
-  Error Invalid_attribute
+type attr_err = Invalid_attribute
 
-let mk_attr2 _lexeme _region = 
+let mk_attr _header _string _region =
   Error Invalid_attribute
 
 (* Predicates *)
diff --git a/src/passes/1-parser/pascaligo/LexerMain.ml b/src/passes/1-parser/pascaligo/LexerMain.ml
index 4f1940204..042b0930a 100644
--- a/src/passes/1-parser/pascaligo/LexerMain.ml
+++ b/src/passes/1-parser/pascaligo/LexerMain.ml
@@ -7,3 +7,8 @@ module IO =
   end
 
 module M = LexerUnit.Make (IO) (Lexer.Make (LexToken))
+
+let () =
+  match M.trace () with
+    Stdlib.Ok _ -> ()
+  | Error msg -> Printf.eprintf "\027[31m%s\027[0m%!" msg
diff --git a/src/passes/1-parser/pascaligo/ParToken.mly b/src/passes/1-parser/pascaligo/ParToken.mly
index 11275b76e..61397c7e3 100644
--- a/src/passes/1-parser/pascaligo/ParToken.mly
+++ b/src/passes/1-parser/pascaligo/ParToken.mly
@@ -12,6 +12,7 @@
 %token   <(LexToken.lexeme * Z.t) Region.reg> Mutez  "<mutez>"
 %token           <LexToken.lexeme Region.reg> Ident  "<ident>"
 %token           <LexToken.lexeme Region.reg> Constr "<constr>"
+%token        <LexToken.attribute Region.reg> Attr   "<attr>"
 
   (* Symbols *)
 
diff --git a/src/passes/1-parser/pascaligo/Parser.mly b/src/passes/1-parser/pascaligo/Parser.mly
index 7325cd1df..21e1947bf 100644
--- a/src/passes/1-parser/pascaligo/Parser.mly
+++ b/src/passes/1-parser/pascaligo/Parser.mly
@@ -5,39 +5,40 @@
 
 open Region
 open AST
-
-type statement_attributes_mixed = 
+(*
+type statement_attributes_mixed =
   PInstr of instruction
 | PData  of data_decl
-| PAttributes of attributes
+| PAttr  of attributes
 
 let attributes_to_statement (statement, statements)  =
-  if (List.length statements = 0) then 
-    match statement with 
-    | PInstr i -> Instr i, []
-    | PData d -> Data d, []
-    | PAttributes a -> 
-      let open! SyntaxError in
-      raise (Error (Detached_attributes a))
-  else (
+  match statements with
+    [] ->
+      (match statement with
+       | PInstr i -> Instr i, []
+       | PData d -> Data d, []
+       | PAttr a ->
+          raise (Scoping.Error (Scoping.Detached_attributes a)))
+  | _ -> (
     let statements = (Region.ghost, statement) :: statements in
     let rec inner result = function
-    | (t, PData  (LocalConst const)) :: (_, PAttributes a) :: rest -> 
+    | (t, PData  (LocalConst const)) :: (_, PAttr a) :: rest ->
       inner (result @ [(t, Data (LocalConst {const with value = {const.value with attributes = a}}))]) rest
-    | (t, PData  (LocalFun func)) :: (_, PAttributes a) :: rest ->
-      inner (result @ [(t, Data (LocalFun {func with value = {func.value with attributes = a}}))]) rest  
+    | (t, PData  (LocalFun func)) :: (_, PAttr a) :: rest ->
+      inner (result @ [(t, Data (LocalFun {func with value = {func.value with attributes = a}}))]) rest
     | (t, PData d) :: rest ->
       inner (result @ [(t, Data d)]) rest
     | (t, PInstr i) :: rest ->
       inner (result @ [(t, Instr i)]) rest
-    | (_, PAttributes _) :: rest ->
+    | (_, PAttr _) :: rest ->
       inner result rest
-    | [] -> 
+    | [] ->
       result
-    in 
+    in
     let result = inner [] statements in
     (snd (List.hd result), List.tl result)
   )
+ *)
 
 (* END HEADER *)
 %}
@@ -145,7 +146,7 @@ contract:
 declaration:
   type_decl  {   TypeDecl $1 }
 | const_decl {  ConstDecl $1 }
-| fun_decl  {    FunDecl $1 }
+| fun_decl   {    FunDecl $1 }
 
 (* Type declarations *)
 
@@ -258,7 +259,7 @@ field_decl:
     and value  = {field_name=$1; colon=$2; field_type=$3}
     in {region; value} }
 
-  
+
 fun_expr:
   "function" parameters ":" type_expr "is" expr {
     let stop   = expr_to_region $6 in
@@ -290,7 +291,7 @@ open_fun_decl:
                     block_with   = Some ($7, $8);
                     return       = $9;
                     terminator   = None;
-                    attributes   = {value = []; region = Region.ghost}}
+                    attributes   = None}
     in {region; value} }
 | "function" fun_name parameters ":" type_expr "is" expr {
     Scoping.check_reserved_name $2;
@@ -305,14 +306,16 @@ open_fun_decl:
                     block_with   = None;
                     return       = $7;
                     terminator   = None;
-                    attributes   = {value = []; region = Region.ghost}}
+                    attributes   = None}
     in {region; value} }
 
 fun_decl:
-  open_fun_decl semi_attributes {
-    let attributes, terminator = $2 in
-    {$1 with value = {$1.value with terminator = terminator; attributes = attributes}}
-  }
+  open_fun_decl maybe_attributes? {
+    match $2 with
+      None -> $1
+    | Some (terminator, attributes) ->
+       let value = {$1.value with terminator; attributes}
+       in {$1 with value} }
 
 parameters:
   par(nsepseq(param_decl,";")) {
@@ -350,7 +353,7 @@ block:
      let statements, terminator = $2 in
      let region = cover $1 $3
      and value  = {opening    = Begin $1;
-                   statements = attributes_to_statement statements;
+                   statements (*= attributes_to_statement statements*);
                    terminator;
                    closing    = End $3}
      in {region; value}
@@ -359,15 +362,15 @@ block:
      let statements, terminator = $3 in
      let region = cover $1 $4
      and value  = {opening    = Block ($1,$2);
-                   statements = attributes_to_statement statements;
+                   statements (*= attributes_to_statement statements*);
                    terminator;
                    closing    = Block $4}
      in {region; value} }
 
 statement:
-  instruction     { PInstr $1 }
-| open_data_decl  { PData  $1 }
-| attributes      { PAttributes $1 }
+  instruction     { (*P*)Instr $1 }
+| open_data_decl  { (*P*)Data  $1 }
+                  (*| attributes      { PAttr  $1 }*)
 
 open_data_decl:
   open_const_decl { LocalConst $1 }
@@ -385,10 +388,9 @@ open_const_decl:
                   equal;
                   init;
                   terminator = None;
-                  attributes = {value = []; region = Region.ghost}}
+                  attributes = None}
     in {region; value} }
 
-
 open_var_decl:
   "var" unqualified_decl(":=") {
     let name, colon, var_type, assign, init, stop = $2 in
@@ -399,8 +401,7 @@ open_var_decl:
                   var_type;
                   assign;
                   init;
-                  terminator = None;
-                  }
+                  terminator=None}
     in {region; value} }
 
 unqualified_decl(OP):
@@ -409,23 +410,20 @@ unqualified_decl(OP):
     let region = expr_to_region $5
     in $1, $2, $3, $4, $5, region }
 
-attributes: 
-  "attributes" "[" nsepseq(String,";") "]" {
-    let region = cover $1 $4 in
-    let value = (Utils.nsepseq_to_list $3) in
-    {region; value}
-  }
+attributes:
+  ne_injection("attributes","<string>") { $1 }
 
-semi_attributes: 
-   /* empty */ { {value = []; region = Region.ghost}, None }
-  | ";" { {value = []; region = Region.ghost}, Some $1 }
-  | ";" attributes ";" { $2, Some $1 }
+maybe_attributes:
+  ";"                { Some $1, None    }
+| ";" attributes ";" { Some $1, Some $2 }
 
 const_decl:
-  open_const_decl semi_attributes {
-    let attributes, terminator = $2 in
-    {$1 with value = {$1.value with terminator = terminator; attributes = attributes }} 
-  }
+  open_const_decl maybe_attributes? {
+    match $2 with
+      None -> $1
+    | Some (terminator, attributes) ->
+       let value = {$1.value with terminator; attributes}
+       in {$1 with value} }
 
 instruction:
   conditional  {        Cond $1 }
@@ -589,7 +587,7 @@ clause_block:
     let statements, terminator = $2 in
     let region = cover $1 $3 in
     let value  = {lbrace = $1;
-                  inside = attributes_to_statement statements, terminator;
+                  inside = (*attributes_to_statement*) statements, terminator;
                   rbrace = $3} in
     ShortBlock {value; region} }
 
diff --git a/src/passes/1-parser/pascaligo/ParserLog.ml b/src/passes/1-parser/pascaligo/ParserLog.ml
index 4a186980e..bacb39a4f 100644
--- a/src/passes/1-parser/pascaligo/ParserLog.ml
+++ b/src/passes/1-parser/pascaligo/ParserLog.ml
@@ -114,12 +114,10 @@ let rec print_tokens state ast =
   Utils.nseq_iter (print_decl state) decl;
   print_token state eof "EOF"
 
-and print_attributes state attributes = 
-  let attributes = List.fold_left (fun all a -> all ^ a.value ^ ";") "" attributes.value in
-  let line =
-    sprintf "attributes[%s]"
-            attributes
-  in Buffer.add_string state#buffer line
+and print_attributes state = function
+  None -> ()
+| Some attr ->
+    print_ne_injection state "attributes" print_string attr
 
 and print_decl state = function
   TypeDecl  decl -> print_type_decl  state decl
@@ -607,7 +605,7 @@ and print_field_assign state {value; _} =
   print_token state equal "=";
   print_expr  state field_expr
 
-and print_update_expr state {value; _} = 
+and print_update_expr state {value; _} =
   let {record; kwd_with; updates} = value in
   print_path state record;
   print_token state kwd_with "with";
@@ -850,19 +848,23 @@ and pp_declaration state = function
     pp_fun_decl state value
 
 and pp_fun_decl state decl =
+  let arity =
+    match decl.attributes with
+      None -> 5
+    | Some _ -> 6 in
   let () =
-    let state = state#pad 5 0 in
+    let state = state#pad arity 0 in
     pp_ident state decl.fun_name in
   let () =
-    let state = state#pad 5 1 in
+    let state = state#pad arity 1 in
     pp_node state "<parameters>";
     pp_parameters state decl.param in
   let () =
-    let state = state#pad 5 2 in
+    let state = state#pad arity 2 in
     pp_node state "<return type>";
     pp_type_expr (state#pad 1 0) decl.ret_type in
   let () =
-    let state = state#pad 5 3 in
+    let state = state#pad arity 3 in
     pp_node state "<body>";
     let statements =
       match decl.block_with with
@@ -870,15 +872,35 @@ and pp_fun_decl state decl =
       | None -> Instr (Skip Region.ghost), [] in
     pp_statements state statements in
   let () =
-    let state = state#pad 5 4 in
+    let state = state#pad arity 4 in
     pp_node state "<return>";
-    pp_expr (state#pad 1 0) decl.return
+    pp_expr (state#pad 1 0) decl.return in
+  let () =
+    match decl.attributes with
+      None -> ()
+    | Some attr ->
+       let state = state#pad arity 5 in
+       pp_node state "<attributes>";
+       pp_attributes (state#pad 1 0) attr
   in ()
 
+and pp_attributes state {value; _} =
+  pp_ne_injection pp_string state value
+
 and pp_const_decl state decl =
-  pp_ident (state#pad 3 0) decl.name;
-  pp_type_expr (state#pad 3 1) decl.const_type;
-  pp_expr (state#pad 3 2) decl.init
+  let arity =
+    match decl.attributes with
+      None -> 3
+    | Some _ -> 4 in
+  pp_ident (state#pad arity 0) decl.name;
+  pp_type_expr (state#pad arity 1) decl.const_type;
+  pp_expr (state#pad arity 2) decl.init;
+  match decl.attributes with
+    None -> ()
+  | Some attr ->
+      let state = state#pad arity 3 in
+      pp_node state "<attributes>";
+      pp_attributes (state#pad 1 0) attr
 
 and pp_type_expr state = function
   TProd cartesian ->
diff --git a/src/passes/1-parser/pascaligo/Scoping.mli b/src/passes/1-parser/pascaligo/Scoping.mli
index 71f8c1244..b62ef7dd2 100644
--- a/src/passes/1-parser/pascaligo/Scoping.mli
+++ b/src/passes/1-parser/pascaligo/Scoping.mli
@@ -6,6 +6,7 @@ type t =
 | Duplicate_variant   of AST.variable
 | Non_linear_pattern  of AST.variable
 | Duplicate_field     of AST.variable
+| Detached_attributes of AST.attributes
 
 type error = t
 
diff --git a/src/passes/1-parser/shared/EvalOpt.ml b/src/passes/1-parser/shared/EvalOpt.ml
index 924a51e08..30277f72f 100644
--- a/src/passes/1-parser/shared/EvalOpt.ml
+++ b/src/passes/1-parser/shared/EvalOpt.ml
@@ -47,9 +47,9 @@ let help language extension () =
   printf "where <input>%s is the %s source file (default: stdin),\n" extension language;
   print "and each <option> (if any) is one of the following:";
   print "  -I <paths>             Library paths (colon-separated)";
-  print "  -c, --copy             Print lexemes of tokens and markup (lexer)";
-  print "  -t, --tokens           Print tokens (lexer)";
-  print "  -u, --units            Print tokens and markup (lexer)";
+  print "  -t, --tokens           Print tokens";
+  print "  -u, --units            Print lexical units";
+  print "  -c, --copy             Print lexemes and markup";
   print "  -q, --quiet            No output, except errors (default)";
   print "      --columns          Columns for source locations";
   print "      --bytes            Bytes for source locations";
diff --git a/src/passes/1-parser/shared/Lexer.mli b/src/passes/1-parser/shared/Lexer.mli
index d01c5387f..1d338d719 100644
--- a/src/passes/1-parser/shared/Lexer.mli
+++ b/src/passes/1-parser/shared/Lexer.mli
@@ -77,8 +77,7 @@ module type TOKEN =
     val mk_string : lexeme -> Region.t -> token
     val mk_bytes  : lexeme -> Region.t -> token
     val mk_constr : lexeme -> Region.t -> token
-    val mk_attr   : lexeme -> Region.t -> (token,  attr_err) result
-    val mk_attr2  : lexeme -> Region.t -> (token,  attr_err) result
+    val mk_attr   : string -> lexeme -> Region.t -> (token, attr_err) result
     val eof       : Region.t -> token
 
     (* Predicates *)
diff --git a/src/passes/1-parser/shared/Lexer.mll b/src/passes/1-parser/shared/Lexer.mll
index ce8c454fb..5b4a335e9 100644
--- a/src/passes/1-parser/shared/Lexer.mll
+++ b/src/passes/1-parser/shared/Lexer.mll
@@ -119,8 +119,7 @@ module type TOKEN =
     val mk_string : lexeme -> Region.t -> token
     val mk_bytes  : lexeme -> Region.t -> token
     val mk_constr : lexeme -> Region.t -> token
-    val mk_attr   : lexeme -> Region.t -> (token,  attr_err) result
-    val mk_attr2  : lexeme -> Region.t -> (token,  attr_err) result
+    val mk_attr   : string -> lexeme -> Region.t -> (token, attr_err) result
     val eof       : Region.t -> token
 
     (* Predicates *)
@@ -178,8 +177,9 @@ module type S =
 
     exception Error of error Region.reg
 
-    val format_error : ?offsets:bool -> [`Byte | `Point] ->
-                       error Region.reg -> file:bool -> string
+    val format_error :
+      ?offsets:bool -> [`Byte | `Point] ->
+      error Region.reg -> file:bool -> string
   end
 
 (* The functorised interface
@@ -436,15 +436,15 @@ module Make (Token: TOKEN) : (S with module Token = Token) =
          Hint: Check the LIGO syntax you use.\n"
     | Invalid_natural ->
         "Invalid natural."
-    | Invalid_attribute -> 
+    | Invalid_attribute ->
         "Invalid attribute."
 
     exception Error of error Region.reg
 
     let format_error ?(offsets=true) mode Region.{region; value} ~file =
-      let  msg = error_to_string value in
-      let  reg = region#to_string ~file ~offsets mode in
-      sprintf "\027[31mLexical error %s:\n%s\027[0m%!" reg msg
+      let msg = error_to_string value
+      and reg = region#to_string ~file ~offsets mode
+      in sprintf "Lexical error %s:\n%s" reg msg
 
     let fail region value = raise (Error Region.{region; value})
 
@@ -506,7 +506,7 @@ module Make (Token: TOKEN) : (S with module Token = Token) =
           let num         = Z.of_string (integral ^ fractional)
           and den         = Z.of_string ("1" ^ String.make (len-index-1) '0')
           and million     = Q.of_string "1000000" in
-          let mutez         = Q.make num den |> Q.mul million in
+          let mutez       = Q.make num den |> Q.mul million in
           let should_be_1 = Q.den mutez in
           if Z.equal Z.one should_be_1 then Some (Q.num mutez) else None
       | exception Not_found -> assert false
@@ -531,22 +531,14 @@ module Make (Token: TOKEN) : (S with module Token = Token) =
         Ok token -> token, state
       | Error Token.Reserved_name -> fail region (Reserved_name lexeme)
 
-    let mk_attr state buffer attr = 
+    let mk_attr header attr state buffer =
       let region, _, state = sync state buffer in
-      match Token.mk_attr attr region with
-        Ok token -> 
-        token, state
-      | Error Token.Invalid_attribute -> 
-        fail region Invalid_attribute
+      match Token.mk_attr header attr region with
+        Ok token ->
+          token, state
+      | Error Token.Invalid_attribute ->
+          fail region Invalid_attribute
 
-    let mk_attr2 state buffer attr = 
-      let region, _, state = sync state buffer in
-      match Token.mk_attr2 attr region with
-        Ok token -> 
-        token, state
-      | Error Token.Invalid_attribute -> 
-        fail region Invalid_attribute
-    
     let mk_constr state buffer =
       let region, lexeme, state = sync state buffer
       in Token.mk_constr lexeme region, state
@@ -560,7 +552,7 @@ module Make (Token: TOKEN) : (S with module Token = Token) =
     let mk_eof state buffer =
       let region, _, state = sync state buffer
       in Token.eof region, state
-    
+
 
 (* END HEADER *)
 }
@@ -580,6 +572,7 @@ let capital    = ['A'-'Z']
 let letter     = small | capital
 let ident      = small (letter | '_' | digit)*
 let constr     = capital (letter | '_' | digit)*
+let attr       = ident | constr
 let hexa_digit = digit | ['A'-'F']
 let byte       = hexa_digit hexa_digit
 let byte_seq   = byte | byte (byte | '_')* byte
@@ -587,8 +580,8 @@ let bytes      = "0x" (byte_seq? as seq)
 let esc        = "\\n" | "\\\"" | "\\\\" | "\\b"
                | "\\r" | "\\t" | "\\x" byte
 let pascaligo_sym = "=/=" | '#' | ":="
-let cameligo_sym = "<>" | "::" | "||" | "&&" | "[@"
-let reasonligo_sym = '!' | "=>" | "!=" | "==" | "++" | "..." | "||" | "&&" | "[@"
+let cameligo_sym = "<>" | "::" | "||" | "&&"
+let reasonligo_sym = '!' | "=>" | "!=" | "==" | "++" | "..." | "||" | "&&"
 
 let symbol =
   ';' | ',' | '(' | ')'| '[' | ']' | '{' | '}'
@@ -614,21 +607,24 @@ rule init state = parse
 | _        { rollback lexbuf; scan state lexbuf  }
 
 and scan state = parse
-  nl              { scan (push_newline state lexbuf) lexbuf }
-| ' '+            { scan (push_space   state lexbuf) lexbuf }
-| '\t'+           { scan (push_tabs    state lexbuf) lexbuf }
-| ident           { mk_ident       state lexbuf |> enqueue   }
-| constr          { mk_constr      state lexbuf |> enqueue   }
-| bytes           { (mk_bytes seq) state lexbuf |> enqueue   }
-| natural 'n'     { mk_nat         state lexbuf |> enqueue   }
-| natural "mutez" { mk_mutez       state lexbuf |> enqueue   }
-| natural "tz"    { mk_tz          state lexbuf |> enqueue   }
-| decimal "tz"    { mk_tz_decimal  state lexbuf |> enqueue   }
-| natural         { mk_int         state lexbuf |> enqueue   }
-| symbol          { mk_sym         state lexbuf |> enqueue   }
-| eof             { mk_eof         state lexbuf |> enqueue   }
-| "[@"  (ident|constr as attr) "]"  { mk_attr state lexbuf attr |> enqueue } 
-| "[@@" (ident|constr as attr) "]"  { mk_attr2 state lexbuf attr |> enqueue } 
+  nl                     { scan (push_newline state lexbuf) lexbuf }
+| ' '+                   { scan (push_space   state lexbuf) lexbuf }
+| '\t'+                  { scan (push_tabs state lexbuf) lexbuf    }
+| ident                  { mk_ident        state lexbuf |> enqueue  }
+| constr                 { mk_constr       state lexbuf |> enqueue  }
+| bytes                  { mk_bytes seq    state lexbuf |> enqueue  }
+| natural 'n'            { mk_nat          state lexbuf |> enqueue  }
+| natural "mutez"        { mk_mutez        state lexbuf |> enqueue  }
+| natural "tz"
+| natural "tez"          { mk_tz           state lexbuf |> enqueue  }
+| decimal "tz"
+| decimal "tez"          { mk_tz_decimal   state lexbuf |> enqueue  }
+| natural                { mk_int          state lexbuf |> enqueue  }
+| symbol                 { mk_sym          state lexbuf |> enqueue  }
+| eof                    { mk_eof          state lexbuf |> enqueue  }
+| "[@"  (attr as a) "]"  { mk_attr "[@"  a state lexbuf |> enqueue  }
+| "[@@" (attr as a) "]"  { mk_attr "[@@" a state lexbuf |> enqueue  }
+
 | '"'  { let opening, _, state = sync state lexbuf in
          let thread = {opening; len=1; acc=['"']} in
          scan_string thread state lexbuf |> mk_string |> enqueue }
@@ -677,8 +673,7 @@ and scan state = parse
     and file         = Filename.basename file in
     let pos          = state.pos#set ~file ~line ~offset:0 in
     let state        = {state with pos} in
-    scan state lexbuf
-  }
+    scan state lexbuf }
 
   (* Some special errors
 
diff --git a/src/passes/1-parser/shared/LexerLog.ml b/src/passes/1-parser/shared/LexerLog.ml
index ce5172045..3497f80fc 100644
--- a/src/passes/1-parser/shared/LexerLog.ml
+++ b/src/passes/1-parser/shared/LexerLog.ml
@@ -1,7 +1,5 @@
 (** Embedding the LIGO lexer in a debug module *)
 
-let sprintf = Printf.sprintf
-
 module type S =
   sig
     module Lexer : Lexer.S
@@ -15,12 +13,12 @@ module type S =
 
     val trace :
       ?offsets:bool -> [`Byte | `Point] ->
-      file_path option -> EvalOpt.command -> unit
+      file_path option -> EvalOpt.command ->
+      (unit, string) Stdlib.result
   end
 
 module Make (Lexer: Lexer.S) : (S with module Lexer = Lexer) =
   struct
-
     module Lexer = Lexer
     module Token = Lexer.Token
 
@@ -49,28 +47,29 @@ module Make (Lexer: Lexer.S) : (S with module Lexer = Lexer) =
 
     type file_path = string
 
-    let trace ?(offsets=true) mode file_path_opt command : unit =
+    let trace ?(offsets=true) mode file_path_opt command :
+          (unit, string) Stdlib.result =
       try
         let Lexer.{read; buffer; close; _} =
-          Lexer.open_token_stream file_path_opt
-        and cout = stdout in
-        let log = output_token ~offsets mode command cout
-        and close_all () = close (); close_out cout in
+          Lexer.open_token_stream file_path_opt in
+        let log = output_token ~offsets mode command stdout
+        and close_all () = close (); close_out stdout in
         let rec iter () =
           match read ~log buffer with
             token ->
-              if Token.is_eof token then close_all ()
+              if   Token.is_eof token
+              then Stdlib.Ok ()
               else iter ()
-          | exception Lexer.Error e ->
+          | exception Lexer.Error error ->
               let file =
                 match file_path_opt with
                   None | Some "-" -> false
-                  |         Some _  -> true in
+                |         Some _  -> true in
               let msg =
-                Lexer.format_error ~offsets mode e ~file
-              in prerr_string msg;
-                 close_all ()
-        in iter ()
-      with Sys_error msg -> Utils.highlight (sprintf "%s\n" msg)
+                Lexer.format_error ~offsets mode ~file error
+              in Stdlib.Error msg in
+          let result = iter ()
+          in (close_all (); result)
+      with Sys_error msg -> Stdlib.Error msg
 
   end
diff --git a/src/passes/1-parser/shared/LexerLog.mli b/src/passes/1-parser/shared/LexerLog.mli
index b0735c5fe..611e22cfa 100644
--- a/src/passes/1-parser/shared/LexerLog.mli
+++ b/src/passes/1-parser/shared/LexerLog.mli
@@ -11,7 +11,8 @@ module type S =
 
     val trace :
       ?offsets:bool -> [`Byte | `Point] ->
-      file_path option -> EvalOpt.command -> unit
+      file_path option -> EvalOpt.command ->
+      (unit, string) Stdlib.result
   end
 
 module Make (Lexer: Lexer.S) : S with module Lexer = Lexer
diff --git a/src/passes/1-parser/shared/LexerUnit.ml b/src/passes/1-parser/shared/LexerUnit.ml
index 8094bdddd..70aadaf5f 100644
--- a/src/passes/1-parser/shared/LexerUnit.ml
+++ b/src/passes/1-parser/shared/LexerUnit.ml
@@ -1,21 +1,20 @@
 (* Functor to build a standalone LIGO lexer *)
 
-module type S =
+module type IO =
   sig
     val ext : string              (* LIGO file extension *)
     val options : EvalOpt.options (* CLI options *)
   end
 
-module Make (IO: S) (Lexer: Lexer.S) =
+module Make (IO: IO) (Lexer: Lexer.S) =
   struct
     open Printf
+    module SSet = Utils.String.Set
+
     (* Error printing and exception tracing *)
 
     let () = Printexc.record_backtrace true
 
-    let external_ text =
-      Utils.highlight (sprintf "External error: %s" text); exit 1
-
     (*  Preprocessing the input source and opening the input channels *)
 
     (* Path for CPP inclusions (#include) *)
@@ -29,7 +28,7 @@ module Make (IO: S) (Lexer: Lexer.S) =
     let prefix =
       match IO.options#input with
         None | Some "-" -> "temp"
-        | Some file ->  Filename.(file |> basename |> remove_extension)
+      | Some file ->  Filename.(file |> basename |> remove_extension)
 
     let suffix = ".pp" ^ IO.ext
 
@@ -42,24 +41,68 @@ module Make (IO: S) (Lexer: Lexer.S) =
     let cpp_cmd =
       match IO.options#input with
         None | Some "-" ->
-           sprintf "cpp -traditional-cpp%s - > %s"
-                          lib_path pp_input
-        | Some file ->
-           sprintf "cpp -traditional-cpp%s %s > %s"
-                          lib_path file pp_input
-
-    let () =
-      if Utils.String.Set.mem "cpp" IO.options#verbose
-      then eprintf "%s\n%!" cpp_cmd;
-      if Sys.command cpp_cmd <> 0 then
-        external_ (sprintf "the command \"%s\" failed." cpp_cmd)
+          sprintf "cpp -traditional-cpp%s - > %s"
+                  lib_path pp_input
+      | Some file ->
+          sprintf "cpp -traditional-cpp%s %s > %s"
+                  lib_path file pp_input
 
     (* Running the lexer on the input file *)
 
+    let scan () : (Lexer.token list, string) Stdlib.result =
+      (* Preprocessing the input *)
+
+      if SSet.mem "cpp" IO.options#verbose
+      then eprintf "%s\n%!" cpp_cmd
+      else ();
+
+      if Sys.command cpp_cmd <> 0 then
+        let msg =
+          sprintf "External error: the command \"%s\" failed." cpp_cmd
+        in Stdlib.Error msg
+      else
+        try
+          let Lexer.{read; buffer; close; _} =
+            Lexer.open_token_stream (Some pp_input) in
+          let close_all () = close (); close_out stdout in
+          let rec read_tokens tokens =
+            match read ~log:(fun _ _ -> ()) buffer with
+              token ->
+                if   Lexer.Token.is_eof token
+                then Stdlib.Ok (List.rev tokens)
+                else read_tokens (token::tokens)
+            | exception Lexer.Error error ->
+                let file =
+                  match IO.options#input with
+                    None | Some "-" -> false
+                  |         Some _  -> true in
+                let msg =
+                  Lexer.format_error ~offsets:IO.options#offsets
+                                     IO.options#mode ~file error
+                in Stdlib.Error msg in
+          let result = read_tokens []
+          in close_all (); result
+        with Sys_error msg -> close_out stdout; Stdlib.Error msg
+
+    (* Tracing the lexing (effectful) *)
+
     module Log = LexerLog.Make (Lexer)
 
-    let () = Log.trace ~offsets:IO.options#offsets
-                       IO.options#mode (Some pp_input)
-                       IO.options#cmd
+    let trace () : (unit, string) Stdlib.result =
+      (* Preprocessing the input *)
+
+      if SSet.mem "cpp" IO.options#verbose
+      then eprintf "%s\n%!" cpp_cmd
+      else ();
+
+      if Sys.command cpp_cmd <> 0 then
+        let msg =
+          sprintf "External error: the command \"%s\" failed." cpp_cmd
+        in Stdlib.Error msg
+      else
+        Log.trace ~offsets:IO.options#offsets
+                  IO.options#mode
+                  (Some pp_input)
+                  IO.options#cmd
 
   end
diff --git a/src/passes/1-parser/shared/LexerUnit.mli b/src/passes/1-parser/shared/LexerUnit.mli
new file mode 100644
index 000000000..11dff93ee
--- /dev/null
+++ b/src/passes/1-parser/shared/LexerUnit.mli
@@ -0,0 +1,13 @@
+(* Functor to build a standalone LIGO lexer *)
+
+module type IO =
+  sig
+    val ext : string              (* LIGO file extension *)
+    val options : EvalOpt.options (* CLI options *)
+  end
+
+module Make (IO: IO) (Lexer: Lexer.S) :
+  sig
+    val scan  : unit -> (Lexer.token list, string) Stdlib.result
+    val trace : unit -> (unit, string) Stdlib.result
+  end
diff --git a/src/passes/1-parser/shared/Memo.ml b/src/passes/1-parser/shared/Memo.ml
new file mode 100644
index 000000000..e375ac31e
--- /dev/null
+++ b/src/passes/1-parser/shared/Memo.ml
@@ -0,0 +1,163 @@
+module Region = Simple_utils.Region
+
+type macro = {
+  origin  : Region.t; (* Not ghost   *)
+  current : Region.t  (* Maybe ghost *)
+}
+
+type location =
+  Loc  of Region.t (* Not ghost *)
+| Link of macro
+
+(* Regions must not be ghosts and strings must not be empty. *)
+
+type valid_lexeme   = string Region.reg (* Not ghost, not empty.    *)
+type invalid_lexeme = string Region.reg (* Not ghost, empty if EOF. *)
+
+type phase =
+  Lexer
+| Parser  of valid_lexeme option * invalid_lexeme
+| Scoping
+
+type error = <
+  location : location;
+  message  : string;   (* Sentence ending with a period *)
+  hint     : string;   (* Suggestion to solve the issue *)
+  help     : string    (* Off-program help *)
+>
+
+type invalid_error = Ghost_region
+
+let check_loc = function
+  Loc reg ->
+    if reg#is_ghost then
+      Stdlib.Error Ghost_region
+    else Ok ()
+| Link {origin; _} ->
+    if origin#is_ghost then
+      Stdlib.Error Ghost_region
+    else Ok ()
+
+let make_error ~location ~message ~hint ~help =
+  match check_loc location with
+    Stdlib.Ok () ->
+      Ok (object
+            method location = location
+            method message  = message
+            method hint     = hint
+            method help     = help
+          end)
+  | Error _ as e -> e
+
+type warning = <
+  location : location;
+  message  : string;   (* Sentence ending with a period *)
+  hint     : string;   (* Idem *)
+>
+
+type invalid_warning = invalid_error
+
+let make_warning ~location ~message ~hint =
+  match check_loc location with
+    Stdlib.Ok () ->
+      Ok (object
+            method location = location
+            method message  = message
+            method hint     = hint
+            method help     = help
+          end)
+  | Error _ as e -> e
+
+type kind =
+  Error    of error   (* Failure of an external invariant *)
+| Internal of string  (* Failure of an internal invariant *)
+| External of string  (* Failure of an external process   *)
+| Warning  of warning
+| Info     of (unit -> string)  (* Log *)
+
+type entry = <
+  phase : phase;
+  kind  : kind
+>
+
+type invalid_entry =
+  Ghost_lexeme
+| Empty_lexeme
+
+let check_phase = function
+  Parser (Some valid_lexeme, invalid_lexeme) ->
+    let open Region in
+    if  valid_lexeme.region#is_ghost
+    ||  invalid_lexeme.region#is_ghost
+    then Stdlib.Error Ghost_lexeme
+    else if valid_lexeme.value = ""
+    then Stdlib.Error Empty_lexeme
+    else Ok ()
+| Parser (None, invalid_lexeme) ->
+    if   invalid_lexeme.region#is_ghost
+    then Stdlib.Error Ghost_lexeme
+    else Ok ()
+| Lexer
+| Scoping -> Ok ()
+
+let make_entry ~phase ~kind =
+  match check_phase phase with
+    Stdlib.Error _ as e -> e
+  | Ok () -> Ok (object
+                  method phase = phase
+                  method kind  = kind
+                end)
+
+type memo = <
+  mode    : [`Byte | `Point]; (* Bytes vs UTF-8 *)
+  offsets : bool;             (* [true] for horizontal offsets *)
+  log     : entry FQueue.t
+>
+
+type t = memo
+
+let empty_memo ~mode ~offsets : memo =
+  object
+    method mode          = mode
+    method offsets       = offsets
+    method log           = FQueue.empty
+    method enqueue entry = {< log = FQueue.enq entry log >}
+    method dequeue       =
+      match FQueue.deq log with
+                     None -> None
+      | Some (log, entry) -> Some ({< log=log >}, entry)
+  end
+
+let sprintf = Printf.sprintf
+
+let string_of_entry ~(file:bool) entry : string =
+  let reg = entry#region#to_string
+              ~file
+              ~offsets:entry#offsets
+              error#mode in
+  let string =
+    match error#phase with
+      Parser (None, invalid_lexeme) ->
+       (match invalid_lexeme.Region.value with
+              "" -> sprintf "Parse error %s" reg (* EOF *)
+        | lexeme -> sprintf "Parse error %s, before \"%s\""
+                           reg lexeme)
+    | Parser (Some valid_lexeme, invalid_lexeme) ->
+       let string =
+         sprintf "Parse error %s, after \"%s\""
+                 reg valid_lexeme.Region.value in
+       (match invalid_lexeme.Region.value with
+              "" -> string (* EOF *)
+        | lexeme -> sprintf "%s and before \"%s\"" string lexeme)
+    | Lexer ->
+        sprintf "Lexical error %s" reg
+    | Scoping ->
+       sprintf "Scoping error %s" reg in
+  let string =
+    string
+    ^ (if error#message = "" then "."
+       else ":\n" ^ error#message) ^ "\n" in
+  let string =
+    string ^ (if error#hint = "" then ""
+              else sprintf "Hint: %s\n" error#hint)
+  in string
diff --git a/src/passes/1-parser/shared/Memo.mli b/src/passes/1-parser/shared/Memo.mli
new file mode 100644
index 000000000..6e89378cd
--- /dev/null
+++ b/src/passes/1-parser/shared/Memo.mli
@@ -0,0 +1,120 @@
+(* This module defines compilation memos. *)
+
+(* Locations *)
+
+module Region = Simple_utils.Region
+
+type macro = private <
+  origin  : Region.t; (* Not ghost   *)
+  current : Region.t  (* Maybe ghost *)
+>
+
+type location = private
+  Loc  of Region.t (* Not ghost *)
+| Link of macro
+
+type invalid_loc = Ghost_region
+
+val make_loc :
+  Region.t -> (location, invalid_loc) Stdlib.result
+
+val make_link :
+  origin:Region.t ->
+  current:Region.t ->
+  (location, invalid_loc) Stdlib.result
+
+type 'a located = <
+  value    : 'a;
+  location : location
+>
+
+val make_located : value:'a -> location:location -> 'a located
+
+(* Lexemes *)
+
+type lexeme = string location (* Not ghost, empty => EOF *)
+
+type window = <
+  valid_lexeme   : lexeme option;
+  invalid_lexeme : lexeme
+>
+
+val make_window : ?valid:lexeme -> invalid:lexeme -> window
+
+(* Compilation phases *)
+
+type phase =
+  Lexer
+| Parser  of window
+| Scoping
+
+(* Messages *)
+
+type message = private string
+
+type invalid_message = Empty_message
+
+val make_message : string -> (message, invalid_error) Stdlib.result
+val string_of_message : message -> string
+
+(* Errors *)
+
+type error = <
+  location : location;
+  message  : message;  (* Non-empty string (ending with a period)      *)
+  hint     : string;   (* Suggestion to solve the issue (may be empty) *)
+  help     : string    (* Off-program help (may be empty)              *)
+>
+
+val make_error :
+  location:location ->
+  message:message ->
+  hint:string ->
+  help:string ->
+  error
+
+(* Warnings *)
+
+type warning = <
+  location : location;
+  message  : message;  (* Non-empty string (ending with a period) *)
+  hint     : string;   (* May empty *)
+>
+
+val make_warning :
+  location:location ->
+  message:message ->
+  hint:string ->
+  warning
+
+(* Kinds of entries *)
+
+type kind =
+  Error    of error   (* Failure of an external invariant             *)
+| Internal of message (* Failure of an internal invariant (non-empty) *)
+| External of message (* Failure of an external process (non-empty)   *)
+| Warning  of warning
+| Info     of (unit -> message)  (* Log (not-empty) *)
+
+type entry = private <
+  phase : phase;
+  kind  : kind
+>
+
+val make_entry : phase:phase -> kind:kind -> entry
+
+val string_of_entry : file:bool -> entry -> string
+
+(* Memos *)
+
+type memo = <
+  mode    : [`Byte | `Point]; (* Bytes vs UTF-8 *)
+  offsets : bool;             (* [true] for horizontal offsets *)
+  log     : entry FQueue.t;
+  enqueue : entry -> memo;
+  dequeue : (memo * entry) option
+>
+
+type t = memo
+
+val empty_memo : mode:[`Byte | `Point] -> offsets:bool -> memo
diff --git a/src/passes/1-parser/shared/ParserAPI.ml b/src/passes/1-parser/shared/ParserAPI.ml
index c55649c0b..50cb6d748 100644
--- a/src/passes/1-parser/shared/ParserAPI.ml
+++ b/src/passes/1-parser/shared/ParserAPI.ml
@@ -90,11 +90,16 @@ module Make (Lexer: Lexer.S)
 
     module Incr = Parser.Incremental
 
-    let incr_contract Lexer.{read; buffer; get_win; close; _} : Parser.ast =
+    let incr_contract memo Lexer.{read; buffer; get_win; close; _} =
       let supplier = I.lexer_lexbuf_to_supplier read buffer
       and failure  = failure get_win in
       let parser   = Incr.contract buffer.Lexing.lex_curr_p in
-      let ast      = I.loop_handle success failure supplier parser
+      let ast      =
+        try I.loop_handle success failure supplier parser with
+          Point (message, valid_opt, invalid) ->
+          let error = Memo. (* TODO *)
+          in Stdlib.Error ()
+
       in close (); ast
 
     let mono_contract = Parser.contract
@@ -117,22 +122,17 @@ module Make (Lexer: Lexer.S)
       let trailer =
         match valid_opt with
           None ->
-          if Lexer.Token.is_eof invalid then ""
-          else let invalid_lexeme = Lexer.Token.to_lexeme invalid in
-               Printf.sprintf ", before \"%s\"" invalid_lexeme
+            if Lexer.Token.is_eof invalid then ""
+            else let invalid_lexeme = Lexer.Token.to_lexeme invalid in
+                 Printf.sprintf ", before \"%s\"" invalid_lexeme
         | Some valid ->
-           let valid_lexeme = Lexer.Token.to_lexeme valid in
-           let s = Printf.sprintf ", after \"%s\"" valid_lexeme in
-           if Lexer.Token.is_eof invalid then s
-           else
-             let invalid_lexeme = Lexer.Token.to_lexeme invalid in
-             Printf.sprintf "%s and before \"%s\"" s invalid_lexeme in
+            let valid_lexeme = Lexer.Token.to_lexeme valid in
+            let s = Printf.sprintf ", after \"%s\"" valid_lexeme in
+            if Lexer.Token.is_eof invalid then s
+            else
+              let invalid_lexeme = Lexer.Token.to_lexeme invalid in
+              Printf.sprintf "%s and before \"%s\"" s invalid_lexeme in
       let header = header ^ trailer in
       header ^ (if msg = "" then ".\n" else ":\n" ^ msg)
 
-    let short_error ?(offsets=true) mode msg (invalid_region: Region.t) =
-      let () = assert (not (invalid_region#is_ghost)) in
-      let header =
-        "Parse error " ^ invalid_region#to_string ~offsets mode in
-      header ^ (if msg = "" then ".\n" else ":\n" ^ msg)
   end
diff --git a/src/passes/1-parser/shared/ParserAPI.mli b/src/passes/1-parser/shared/ParserAPI.mli
index 9a3bca76e..cbd26e317 100644
--- a/src/passes/1-parser/shared/ParserAPI.mli
+++ b/src/passes/1-parser/shared/ParserAPI.mli
@@ -2,6 +2,9 @@
 
 module Region = Simple_utils.Region
 
+(* The signature generated by Menhir with additional type definitions
+   for [ast] and [expr]. *)
+
 module type PARSER =
   sig
     (* The type of tokens. *)
@@ -44,30 +47,24 @@ module Make (Lexer: Lexer.S)
             (Parser: PARSER with type token = Lexer.Token.token)
             (ParErr: sig val message : int -> string end) :
   sig
-    (* Monolithic and incremental APIs of Menhir for parsing *)
+    (* The monolithic API of Menhir with memos *)
 
     val mono_contract :
-      (Lexing.lexbuf -> Lexer.token) -> Lexing.lexbuf -> Parser.ast
-    val incr_contract :
-      Lexer.instance -> Parser.ast
+      (Lexing.lexbuf -> Lexer.token) ->
+      Lexing.lexbuf ->
+      (Parser.ast, string) Stdlib.result
 
     val mono_expr :
-      (Lexing.lexbuf -> Lexer.token) -> Lexing.lexbuf -> Parser.expr
+      (Lexing.lexbuf -> Lexer.token) ->
+      Lexing.lexbuf ->
+      (Parser.expr, string) Stdlib.result
+
+    (* Incremental API of Menhir with memos *)
+
+    val incr_contract :
+      Lexer.instance -> (Parser.ast, string) Stdlib.result
+
     val incr_expr :
-      Lexer.instance -> Parser.expr
-
-    (* Error handling *)
-
-    type message = string
-    type valid   = Parser.token
-    type invalid = Parser.token
-    type error   = message * valid option * invalid
-
-    exception Point of error
-
-    val format_error :
-      ?offsets:bool -> [`Byte | `Point] -> error -> string
-
-    val short_error :
-      ?offsets:bool -> [`Byte | `Point] -> message -> Region.t -> string
+      Lexer.instance ->
+      (Parser.expr, string) Stdlib.result
   end
diff --git a/src/passes/1-parser/shared/ParserUnit.ml b/src/passes/1-parser/shared/ParserUnit.ml
index adedad6f6..2aaae54ee 100644
--- a/src/passes/1-parser/shared/ParserUnit.ml
+++ b/src/passes/1-parser/shared/ParserUnit.ml
@@ -88,7 +88,6 @@ module Make (Lexer: Lexer.S)
     module Front = ParserAPI.Make (Lexer)(Parser)(ParErr)
 
     let format_error = Front.format_error
-    let short_error  = Front.short_error
 
     (* Parsing an expression *)
 
@@ -96,25 +95,28 @@ module Make (Lexer: Lexer.S)
           (AST.expr, string) Stdlib.result =
       let close_all () =
         lexer_inst.Lexer.close (); close_out stdout in
+      let lexbuf = lexer_inst.Lexer.buffer in
       let expr =
-        if IO.options#mono then
-          Front.mono_expr tokeniser lexer_inst.Lexer.buffer
-        else
-          Front.incr_expr lexer_inst in
+        try
+          if IO.options#mono then
+            Front.mono_expr tokeniser lexbuf
+          else
+            Front.incr_expr lexer_inst
+        with exn -> close_all (); raise exn in
       let () =
-        if SSet.mem "ast-tokens" IO.options#verbose
-        then begin
-               Buffer.clear output;
-               ParserLog.print_expr state expr;
-               Buffer.output_buffer stdout output
-             end in
+        if SSet.mem "ast-tokens" IO.options#verbose then
+          begin
+            Buffer.clear output;
+            ParserLog.print_expr state expr;
+            Buffer.output_buffer stdout output
+          end in
       let () =
-        if SSet.mem "ast" IO.options#verbose
-        then begin
-               Buffer.clear output;
-               ParserLog.pp_expr state expr;
-               Buffer.output_buffer stdout output
-             end
+        if SSet.mem "ast" IO.options#verbose then
+          begin
+            Buffer.clear output;
+            ParserLog.pp_expr state expr;
+            Buffer.output_buffer stdout output
+          end
       in close_all (); Ok expr
 
     (* Parsing a contract *)
@@ -123,27 +125,28 @@ module Make (Lexer: Lexer.S)
         : (AST.t, string) Stdlib.result =
       let close_all () =
         lexer_inst.Lexer.close (); close_out stdout in
+      let lexbuf = lexer_inst.Lexer.buffer in
       let ast =
         try
           if IO.options#mono then
-            Front.mono_contract tokeniser lexer_inst.Lexer.buffer
+            Front.mono_contract tokeniser lexbuf
           else
             Front.incr_contract lexer_inst
         with exn -> close_all (); raise exn in
       let () =
-        if SSet.mem "ast" IO.options#verbose
-        then begin
-               Buffer.clear output;
-               ParserLog.pp_ast state ast;
-               Buffer.output_buffer stdout output
-             end in
+        if SSet.mem "ast-tokens" IO.options#verbose then
+          begin
+            Buffer.clear output;
+            ParserLog.print_tokens state ast;
+            Buffer.output_buffer stdout output
+          end in
       let () =
-        if SSet.mem "ast-tokens" IO.options#verbose
-        then begin
-               Buffer.clear output;
-               ParserLog.print_tokens state ast;
-               Buffer.output_buffer stdout output
-             end
+        if SSet.mem "ast" IO.options#verbose then
+          begin
+            Buffer.clear output;
+            ParserLog.pp_ast state ast;
+            Buffer.output_buffer stdout output
+          end
       in close_all (); Ok ast
 
     (* Wrapper for the parsers above *)
@@ -157,7 +160,7 @@ module Make (Lexer: Lexer.S)
 
       if Sys.command cpp_cmd <> 0 then
         let msg =
-          sprintf "External error: the command \"%s\" failed." cpp_cmd
+          sprintf "External error: \"%s\" failed." cpp_cmd
         in Stdlib.Error msg
       else
         (* Instantiating the lexer *)
diff --git a/src/passes/1-parser/shared/ParserUnit.mli b/src/passes/1-parser/shared/ParserUnit.mli
index ef5b8c4b5..59e665273 100644
--- a/src/passes/1-parser/shared/ParserUnit.mli
+++ b/src/passes/1-parser/shared/ParserUnit.mli
@@ -46,9 +46,6 @@ module Make (Lexer: Lexer.S)
     val format_error :
       ?offsets:bool -> [`Byte | `Point] -> error -> string
 
-    val short_error :
-      ?offsets:bool -> [`Byte | `Point] -> message -> Region.t -> string
-
     (* Parsers *)
 
     val parse :
diff --git a/vendors/ligo-utils/simple-utils/pos.ml b/vendors/ligo-utils/simple-utils/pos.ml
index d489da57f..4c4677bd8 100644
--- a/vendors/ligo-utils/simple-utils/pos.ml
+++ b/vendors/ligo-utils/simple-utils/pos.ml
@@ -23,9 +23,10 @@ type t = <
 
   is_ghost : bool;
 
-  to_string : ?offsets:bool -> [`Byte | `Point] -> string;
-  compact   : ?offsets:bool -> [`Byte | `Point] -> string;
-  anonymous : ?offsets:bool -> [`Byte | `Point] -> string
+  to_string :
+    ?file:bool -> ?offsets:bool -> [`Byte | `Point] -> string;
+  compact :
+    ?file:bool -> ?offsets:bool -> [`Byte | `Point] -> string;
 >
 
 type pos = t
@@ -55,14 +56,15 @@ let make ~byte ~point_num ~point_bol =
     method set_offset offset =
       {< byte = Lexing.{byte with pos_cnum = byte.pos_bol + offset} >}
 
-    method set ~file ~line ~offset =
-      let pos = self#set_file file in
+    method set ?file ~line ~offset =
+      let pos =
+        match file with
+          None -> self
+        | Some name -> self#set_file name in
       let pos = pos#set_line line in
       let pos = pos#set_offset offset
       in pos
 
-    (* The string must not contain '\n'. See [new_line]. *)
-
     method shift_bytes len =
       {< byte = Lexing.{byte with pos_cnum = byte.pos_cnum + len};
          point_num = point_num + len >}
@@ -77,11 +79,13 @@ let make ~byte ~point_num ~point_bol =
                           pos_bol  = byte.pos_cnum};
          point_bol = point_num >}
 
+    (* The string must not contain '\n'. See [add_line]. *)
+
     method new_line string =
       let len = String.length string
       in (self#shift_bytes len)#add_nl
 
-    method is_ghost = byte = Lexing.dummy_pos
+    method is_ghost = (byte = Lexing.dummy_pos)
 
     method file = byte.Lexing.pos_fname
 
@@ -99,24 +103,30 @@ let make ~byte ~point_num ~point_bol =
 
     method byte_offset = byte.Lexing.pos_cnum
 
-    method to_string ?(offsets=true) mode =
-      let offset = self#offset mode in
-      let horizontal, value =
-        if offsets then "character", offset else "column", offset + 1
-      in sprintf "File \"%s\", line %i, %s %i"
-           self#file self#line horizontal value
-
-    method compact ?(offsets=true) mode =
+    method to_string ?(file=true) ?(offsets=true) mode =
       if self#is_ghost then "ghost"
       else
         let offset = self#offset mode in
-        sprintf "%s:%i:%i"
-          self#file self#line (if offsets then offset else offset + 1)
+        let horizontal, value =
+          if offsets then
+            "character", offset
+          else "column", offset + 1 in
+        if file && self#file <> "" then
+          sprintf "File \"%s\", line %i, %s %i"
+                  self#file self#line horizontal value
+        else sprintf "Line %i, %s %i"
+                     self#line horizontal value
 
-    method anonymous ?(offsets=true) mode =
-      if   self#is_ghost then "ghost"
-      else sprintf "%i:%i" self#line
-             (if offsets then self#offset mode else self#column mode)
+    method compact ?(file=true) ?(offsets=true) mode =
+      if self#is_ghost then "ghost"
+      else
+        let horizontal =
+          if offsets then self#offset mode
+          else self#column mode in
+        if file && self#file <> "" then
+          sprintf "%s:%i:%i" self#file self#line horizontal
+        else
+          sprintf "%i:%i" self#line horizontal
 end
 
 let from_byte byte =
@@ -126,7 +136,9 @@ let from_byte byte =
 
 let ghost = make ~byte:Lexing.dummy_pos ~point_num:(-1) ~point_bol:(-1)
 
-let min = make ~byte:Lexing.dummy_pos ~point_num:0 ~point_bol:0
+let min file =
+  let pos = make ~byte:Lexing.dummy_pos ~point_num:0 ~point_bol:0
+  in pos#set_file file
 
 (* Comparisons *)
 
diff --git a/vendors/ligo-utils/simple-utils/pos.mli b/vendors/ligo-utils/simple-utils/pos.mli
index dbeb3eeab..376cb3202 100644
--- a/vendors/ligo-utils/simple-utils/pos.mli
+++ b/vendors/ligo-utils/simple-utils/pos.mli
@@ -58,23 +58,36 @@
      {li The call [pos#byte_offset] is the offset of the position
          [pos] since the begininng of the file, counted in bytes.}}
  *)
-type t = <
+
+type invalid_pos = [
+  `Invalid_line
+| `Invalid_offset
+]
+
+type invalid_line   = `Invalid_line
+type invalid_offset = `Invalid_offset
+type invalid_nl     = `Invalid_newline
+
+type t = private <
   (* Payload *)
 
   byte       : Lexing.position;
-  point_num  : int;
-  point_bol  : int;
-  file       : string;
-  line       : int;
+  point_num  : int;    (* point_num >= point_bol *)
+  point_bol  : int;    (* point_bol >= 0         *)
+  file       : string; (* May be empty           *)
+  line       : int;    (* line > 0               *)
 
   (* Setters *)
 
   set_file   : string -> t;
-  set_line   : int -> t;
-  set_offset : int -> t;
-  set        : file:string -> line:int -> offset:int -> t;
+  set_line   : int -> (t, invalid_line) Stdlib.result;
+  set_offset : int -> (t, invalid_offset) Stdlib.result;
 
-  new_line : string -> t;
+  set : ?file:string -> line:int -> offset:int ->
+        (t, invalid_pos) Stdlib.result;
+
+  (* String must be "\n" or "\c\r" *)
+  new_line : string -> (t, invalid_newline) Stdlib.result
   add_nl   : t;
 
   shift_bytes     : int -> t;
@@ -93,9 +106,10 @@ type t = <
 
   (* Conversions to [string] *)
 
-  to_string : ?offsets:bool -> [`Byte | `Point] -> string;
-  compact   : ?offsets:bool -> [`Byte | `Point] -> string;
-  anonymous : ?offsets:bool -> [`Byte | `Point] -> string
+  to_string :
+    ?file:bool -> ?offsets:bool -> [`Byte | `Point] -> string;
+  compact :
+    ?file:bool -> ?offsets:bool -> [`Byte | `Point] -> string;
 >
 
 (** A shorthand after an [open Pos].
@@ -104,18 +118,22 @@ type pos = t
 
 (** {1 Constructors} *)
 
-val make      : byte:Lexing.position -> point_num:int -> point_bol:int -> t
-val from_byte : Lexing.position -> t
+val make :
+  byte:Lexing.position -> point_num:int -> point_bol:int ->
+  (t, invalid_pos) Stdlin.result
+
+val from_byte :
+  Lexing.position -> (t, invalid_pos) Stdlib.result
 
 (** {1 Special positions} *)
 
-(** The value [ghost] is the same as {! Lexing.dummy_pos}.
+(** The value [ghost] based on the same as {! Lexing.dummy_pos}.
  *)
 val ghost : t
 
-(** Lexing convention: line [1], offsets to [0] and file to [""].
+(** Lexing convention: line [1], offset to [0].
  *)
-val min : t
+val min : file:string -> t
 
 (** {1 Comparisons} *)
 
diff --git a/vendors/ligo-utils/simple-utils/region.ml b/vendors/ligo-utils/simple-utils/region.ml
index c19a1a776..21e47a605 100644
--- a/vendors/ligo-utils/simple-utils/region.ml
+++ b/vendors/ligo-utils/simple-utils/region.ml
@@ -101,8 +101,8 @@ let make ~(start: Pos.t) ~(stop: Pos.t) =
         if start#is_ghost || stop#is_ghost then "ghost"
         else
           let prefix    = if file then start#file ^ ":" else ""
-          and start_str = start#anonymous ~offsets mode
-          and stop_str  = stop#anonymous ~offsets mode in
+          and start_str = start#compact ~file:false ~offsets mode
+          and stop_str  = stop#compact ~file:false ~offsets mode in
           if start#file = stop#file then
             if start#line = stop#line then
               sprintf "%s%s-%i" prefix start_str
diff --git a/vendors/ligo-utils/simple-utils/region.mli b/vendors/ligo-utils/simple-utils/region.mli
index a2f77c057..f9e1d5a53 100644
--- a/vendors/ligo-utils/simple-utils/region.mli
+++ b/vendors/ligo-utils/simple-utils/region.mli
@@ -54,9 +54,9 @@
 
       {li The method [compact] has the same signature as and calling
           convention as [to_string], except that the resulting string
-          is more compact.}}
+          is shorter (usually for debugging or tracing).}}
  *)
-type t = <
+type t = private <
   start : Pos.t;
   stop  : Pos.t;
 
@@ -86,9 +86,9 @@ type t = <
  *)
 type region = t
 
-(** The type ['a reg] enables the concept of something of type ['a] to
+(** The type ['a reg] enables the concept of some value of type ['a] to
     be related to a region in a source file.
- *)
+*)
 type 'a reg = {region: t; value: 'a}
 
 (* {1 Constructors} *)