From be9ebc95c0d02da4bcc2af91912176905d223fe4 Mon Sep 17 00:00:00 2001
From: raskad <32105367+raskad@users.noreply.github.com>
Date: Thu, 12 Jan 2023 00:12:29 +0000
Subject: [PATCH] Add regex literal early errors (#2517)

This Pull Request changes the following:

- Parse regex literals via `regress` during parsing to return errors in the regex as early syntax errors.
---
 Cargo.lock                    | 1 +
 boa_parser/Cargo.toml         | 1 +
 boa_parser/src/lexer/regex.rs | 8 ++++++++
 3 files changed, 10 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index 8f3de16a0d0..bef5c59f246 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -300,6 +300,7 @@ dependencies = [
  "fast-float",
  "num-bigint",
  "num-traits",
+ "regress",
  "rustc-hash",
 ]
 
diff --git a/boa_parser/Cargo.toml b/boa_parser/Cargo.toml
index a4d5601ce0c..f08c366de2f 100644
--- a/boa_parser/Cargo.toml
+++ b/boa_parser/Cargo.toml
@@ -21,3 +21,4 @@ fast-float = "0.2.0"
 num-traits = "0.2.15"
 bitflags = "1.3.2"
 num-bigint = "0.4.3"
+regress = "0.4.1"
diff --git a/boa_parser/src/lexer/regex.rs b/boa_parser/src/lexer/regex.rs
index 41d6270dc46..d416b853a4e 100644
--- a/boa_parser/src/lexer/regex.rs
+++ b/boa_parser/src/lexer/regex.rs
@@ -5,6 +5,7 @@ use bitflags::bitflags;
 use boa_ast::Position;
 use boa_interner::{Interner, Sym};
 use boa_profiler::Profiler;
+use regress::Regex;
 use std::{
     io::{self, ErrorKind, Read},
     str::{self, FromStr},
@@ -120,6 +121,13 @@ impl<R> Tokenizer<R> for RegexLiteral {
 
         let flags_str = unsafe { str::from_utf8_unchecked(flags.as_slice()) };
         if let Ok(body_str) = str::from_utf8(body.as_slice()) {
+            if let Err(error) = Regex::with_flags(body_str, flags_str) {
+                return Err(Error::Syntax(
+                    format!("Invalid regular expression literal: {error}").into(),
+                    start_pos,
+                ));
+            }
+
             Ok(Token::new(
                 TokenKind::regular_expression_literal(
                     interner.get_or_intern(body_str),