Support decimal codes in string literals

lib/lexer.mll

@@ -170,7 +170,7 @@ rule read =
     { let v = decimal_code c d u in
       if v > 255 then
         raise (SyntaxError
-          (Printf.sprintf "illegal escape sequence \\%c%c%c" c d u))
+          (Printf.sprintf "Illegal escape sequence \\%c%c%c" c d u))
       else
         U8 (Char.chr v) }
   | "'" '\\' 'x'
@@ -216,6 +216,14 @@ and read_string buf =
   | '\\' 'r'  { Buffer.add_char buf '\r'; read_string buf lexbuf }
   | '\\' 't'  { Buffer.add_char buf '\t'; read_string buf lexbuf }
   | '\\' '"'  { Buffer.add_char buf '"'; read_string buf lexbuf }
+  | '\\' (['0'-'9'] as c) (['0'-'9'] as d) (['0'-'9']  as u)
+    { let v = decimal_code c d u in
+        if v > 255 then
+          raise (SyntaxError (Printf.sprintf
+              "Illegal backslash escape in string: '\\%c%c%c'" c d u))
+        else
+          Buffer.add_char buf (Char.chr v);
+          read_string buf lexbuf }
   | [^ '"' '\\' '\n' '\r']+
     { Buffer.add_string buf (Lexing.lexeme lexbuf);
       read_string buf lexbuf

test/typing.ml

@@ -65,6 +65,10 @@ let test_const_i32 () = test "i32" "let a = 123i32\na"
 let test_const_neg_i32 () = test "i32" "let a = -123i32\na"
 let test_const_f32 () = test "f32" "let a = 1.0f32\na"
 let test_const_neg_f32 () = test "f32" "let a = -1.0f32\na"
+
+let test_const_string_ansi () =
+  test "string/t" "let s = \"\\027[2K\ram idling: \"\ns"
+
 let test_hint_int () = test "int" "let a : int = 1\na"
 let test_func_id () = test "('a) -> 'a" "fun (a): copy(a)"
 let test_func_id_hint () = test "(int) -> int" "fun (a : int): a"
@@ -1426,6 +1430,7 @@ let () =
           case "-i32" test_const_neg_i32;
           case "f32" test_const_f32;
           case "-f32" test_const_neg_f32;
+          case "string ansi" test_const_string_ansi;
         ] );
       ("hints", [ case "int" test_hint_int ]);
       ( "funcs",