From c4fe4159c173c5cd03227f1ca4404068974f984d Mon Sep 17 00:00:00 2001
From: Tyson Smith <tyson.w.smith@gmail.com>
Date: Thu, 30 Apr 2026 17:06:05 -0700
Subject: [PATCH] feat(FTB): support AssertedCast error messages

---
 FTB/AssertionHelper.py                      |  4 ++++
 FTB/tests/fixtures/assert_asserted_cast.txt |  1 +
 FTB/tests/test_AssertionHelper.py           | 14 ++++++++++++++
 3 files changed, 19 insertions(+)
 create mode 100644 FTB/tests/fixtures/assert_asserted_cast.txt

diff --git a/FTB/AssertionHelper.py b/FTB/AssertionHelper.py
index df5e260e2..3876a796f 100644
--- a/FTB/AssertionHelper.py
+++ b/FTB/AssertionHelper.py
@@ -83,6 +83,10 @@ def getAssertion(output: list[str]) -> str | list[str] | None:
             endRegex = RE_V8_END
             lastLine = [line]
             haveFatalAssertion = True
+        elif line.startswith("AssertedCast error:"):
+            # Firefox AssertedCast error (mozilla/Casting.h)
+            lastLine = line
+            haveFatalAssertion = True
         elif "Assertion" in line and "failed" in line:
             # Firefox ANGLE assertion
             lastLine = line
diff --git a/FTB/tests/fixtures/assert_asserted_cast.txt b/FTB/tests/fixtures/assert_asserted_cast.txt
new file mode 100644
index 000000000..c79194160
--- /dev/null
+++ b/FTB/tests/fixtures/assert_asserted_cast.txt
@@ -0,0 +1 @@
+AssertedCast error: Cannot cast -32769 from int32_t to uint32_t: out of range
diff --git a/FTB/tests/test_AssertionHelper.py b/FTB/tests/test_AssertionHelper.py
index d4883f6ec..17e144ad2 100644
--- a/FTB/tests/test_AssertionHelper.py
+++ b/FTB/tests/test_AssertionHelper.py
@@ -266,6 +266,20 @@ def test_AssertionHelperTestCPPUnhandledException():
     _check_regex_matches(err, sanitizedMsg)
 
 
+def test_AssertionHelperTestAssertedCast():
+    err = (FIXTURE_PATH / "assert_asserted_cast.txt").read_text().splitlines()
+
+    sanitizedMsg = AssertionHelper.getSanitizedAssertionPattern(
+        AssertionHelper.getAssertion(err)
+    )
+    expectedMsg = (
+        r"AssertedCast error: Cannot cast -[0-9]{2,} from int[0-9]{2,}_t to "
+        r"uint[0-9]{2,}_t: out of range"
+    )
+    assert sanitizedMsg == expectedMsg
+    _check_regex_matches(err, sanitizedMsg)
+
+
 def test_AssertionHelperTestRustPanic01():
     err = (FIXTURE_PATH / "assert_rust_panic1.txt").read_text().splitlines()
     sanitizedMsg = AssertionHelper.getSanitizedAssertionPattern(