bug(toml): parse duplicates the character next to reserved escape sequences

[babiabeo]

Describe the bug

According to the TOML spec, escape sequences that are not listed here are reserved:

\b         - backspace       (U+0008)
\t         - tab             (U+0009)
\n         - linefeed        (U+000A)
\f         - form feed       (U+000C)
\r         - carriage return (U+000D)
\"         - quote           (U+0022)
\\         - backslash       (U+005C)
\uXXXX     - unicode         (U+XXXX)
\UXXXXXXXX - unicode         (U+XXXXXXXX)

But when I parse a string that includes a reserved escape sequence, the parser duplicates the character next to it.

Steps to Reproduce

import { parse } from "https://deno.land/std@0.212.0/toml/mod.ts";

parse('a = "a\\0b"'); // { a: "abb" }

Expected behavior

There are 2 cases that I expected:

• Ignores the reserved escape sequence:

parse('a = "a\\0b"'); // { a: "ab" }

• Throws an error as specified in the spec:

All other escape sequences not listed above are reserved; if they are used, TOML should produce an error.

Environment

• OS:
• deno version: 1.39.3
• std version: 0.212.0