Concept cannot be used as a type

Hello!

So far, I can't reproduce the issue on my side in a default "Hello, World!" project (File | New Project > C++ Executable > Create):

1. What CLion version do you use?
2. On what OS do you use CLion?
3. What compiler do you use in CLion (name and version)?
4. Is the “Use the ReSharper C++ language engine (CLion Nova)” option enabled or disabled in File | Settings | Advanced Settings?
5. Is the issue reproducible in a default "Hello, World!" project (File | New Project > C++ Executable > Create)?

1.

CLion 2024.3.5
Build #CL-243.26053.34, built on March 20, 2025
Licensed to Alexander Kern
Subscription is active until March 10, 2026.
For educational use only.
Runtime version: 21.0.6+8-b631.39 amd64 (JCEF 122.1.9)
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o.
Toolkit: sun.awt.X11.XToolkit
Linux 6.11.0-24-generic
Ubuntu 24.04.2 LTS; glibc: 2.39
.NET Core v8.0.11 x64 (Server GC)
GC: G1 Young Generation, G1 Concurrent GC, G1 Old Generation
Memory: 2048M
Cores: 12
Registry:
 actionSystem.update.actions.warn.dataRules.on.edt=false
 debugger.attach.dialog.enabled=true
 run.processes.with.pty=TRUE
 ide.experimental.ui=true
 ide.slow.operations.assertion=false
 cache.folding.model.on.disk=false
 llm.show.ai.promotion.window.on.start=false
Current Desktop: ubuntu:GNOME
 

2. Ubuntu 24.04

3. gcc 13.3.0

4. Enabled

5. Nope, not reproducible. There it works.

This brings us to the more complicated fact that I use a compilation database, which is compiled externally like this: 

https://www.jetbrains.com/help/clion/ros2-tutorial.html

Could you please invalidate all the caches (https://www.jetbrains.com/help/clion/invalidate-caches.html, please select all the options)? Does the issue happen after that?

Anna Falevskaya Unfortunately, this did not resolve it. Cleared all caches, deleted all build files, rebuild freshly, still linter issues.

Laxnpander, in this case, I kindly ask you to provide a simple project with which the issue can be reproduced to clion-support at jetbrains.com.