Description

CodeQL's Swift analysis fails with an internal error during GitHub code scanning (default setup) on a public Swift/SwiftPM macOS project:

CodeQL encountered an unexpected internal error with the following message:
Assertion failed: found != SwiftMangler::preloadedExtensionOrFilePrivateValueIndexes.end(). declaration not found within parent
Some or all of the Swift analysis may have failed.

Environment

• GitHub code scanning default setup, language: swift
• GitHub-hosted macOS runner
• Occurred ~2026-07-20, reproducible across scans

Reproduction

Public repo that triggers it: https://github.com/inequitas/performancemonitor — a Swift Package Manager macOS menu-bar app (SwiftUI/AppKit), Swift 5.10 tools, no third-party dependencies. The codebase uses fileprivate/private declarations and extensions extensively, which — given the assertion name (preloadedExtensionOrFilePrivateValueIndexes) — may be related.

Impact

Swift analysis fails/is incomplete, so code scanning produces no reliable Swift results; we've had to disable CodeQL for the repo.

Happy to help narrow down a minimal repro if useful.