IntelliJ IDEA shows false error on ternary expression in Java code

Symptoms

IntelliJ IDEA displays a false error or warning on valid Java ternary expressions. The code compiles and runs correctly, but the editor highlights it as an error.

import java.util.Objects;


public class TestInteger {

    public static void main(String[] args) {
        Integer mainstatus = Objects.equals(1, 2)
                ? (
                Objects.equals(new Integer(4), 1) ? 2 : 3
        )
                : Objects.equals(1, 3) ? 0 : 4 + 2;

        System.out.println(mainstatus);
    }

}

Cause

This issue is caused by the third-party Manifold plugin (manifold-ij), which interferes with IntelliJ IDEA's built-in Java code analysis.

Resolution

1. Disable the Manifold plugin:

   • Go to Settings | Plugins | Installed
   • Find manifold-ij and uncheck it
   • Restart IntelliJ IDEA

2. If you need the Manifold plugin functionality, report the issue to the plugin's issue tracker: https://github.com/manifold-systems/manifold/issues

Notes

• Invalidating caches (File | Invalidate Caches) does not resolve this issue since the root cause is the plugin, not corrupted caches.
• The issue was confirmed by examining IDE logs, which revealed the Manifold plugin as the source of the incorrect error highlighting.

Related issue

IDEA-388481