Add file extraction in error output

main.ml

@@ -31,11 +31,13 @@ let process source_code_file no_typing =
         localisation l1 source_code_file;
         localisation l2 source_code_file;
         eprintf "Typing error: %s@." s;
+        extract_in_file source_code_file l1 l2;
         exit 1
     | Compiler.Error ((l1,l2),s) ->
         localisation l1 source_code_file;
         localisation l2 source_code_file;
         eprintf "Compilation error: %s@." s;
+        extract_in_file source_code_file l1 l2;
         exit 1
 
 let _ =

utils.ml

@@ -21,5 +21,20 @@ let localisation pos file =
   let c = pos.pos_cnum - pos.pos_bol + 1 in
     eprintf "File \"%s\", line %d, characters %d-%d:\n" file l (c-1) c
 
+let extract_in_file file pos1 pos2 =
+  let current_line = ref "" in
+  let l1 = pos1.pos_lnum in
+  let l2 = pos2.pos_lnum in
+  try
+    let ic = open_in file in
+      eprintf "---- view in file ----\n";
+      for i=0 to (l2-1) do
+        current_line := input_line ic;
+        if i >= (l1-1) && i <= (l2-1) then eprintf "%s\n" !current_line
+      done;
+      eprintf "----\n";
+      close_in ic;
+  with exc -> ()
+
 let counter_from n =
   let r = ref (n-1) in fun () -> incr r; !r