From 92dbba6c5d4b0d5e7f2e9d6efb09fc733ee83184 Mon Sep 17 00:00:00 2001
From: Addison Crump <me@addisoncrump.info>
Date: Tue, 8 Mar 2022 18:17:15 +0000
Subject: [PATCH] Prevent breaks without loop or switch from causing panics
 (#1860)

This PR changes the following:

- Replaces a panic with a syntax error when a break is used outside of a loop or switch
- Adds a test for that
---
 boa_engine/src/bytecompiler.rs |  6 +++++-
 boa_engine/src/tests.rs        | 14 ++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/boa_engine/src/bytecompiler.rs b/boa_engine/src/bytecompiler.rs
index ad709525e5..3dd8cac706 100644
--- a/boa_engine/src/bytecompiler.rs
+++ b/boa_engine/src/bytecompiler.rs
@@ -1596,7 +1596,11 @@ impl<'b> ByteCompiler<'b> {
                 } else {
                     self.jump_info
                         .last_mut()
-                        .expect("no jump information found")
+                        .ok_or_else(|| {
+                            self.context.construct_syntax_error(
+                                "unlabeled break must be inside loop or switch",
+                            )
+                        })?
                         .breaks
                         .push(label);
                 }
diff --git a/boa_engine/src/tests.rs b/boa_engine/src/tests.rs
index a8ee0730b3..5500d3d34e 100644
--- a/boa_engine/src/tests.rs
+++ b/boa_engine/src/tests.rs
@@ -442,6 +442,20 @@ fn test_invalid_break_target() {
     assert!(Context::default().eval(src).is_err());
 }
 
+#[test]
+fn test_invalid_break() {
+    let mut context = Context::default();
+    let src = r#"
+        break;
+        "#;
+
+    let string = forward(&mut context, src);
+    assert_eq!(
+        string,
+        "Uncaught \"SyntaxError\": \"unlabeled break must be inside loop or switch\""
+    );
+}
+
 #[test]
 fn test_invalid_continue_target() {
     let mut context = Context::default();