Multiple definition errors with Clang when using CPP modules

This bug makes absolutely no sense because there are seemingly unlimited places where you can comment out or uncomment a section and it goes away. The error given is:

error: definition with same mangled name '_ZN6jeaiiiL6digitsE' as another definition

A minimal example is given here on Godbolt. And here as a repo you can download.

On my computer I am using Clang version 22.0.0, but the Godbolt version is 21.1.0 and the same thing happens.

The source looks something like this:

main.cpp:

#include "./StringClass.h"
#include <exception>

import glm_module; // MOVING THE IMPORT HIGHER BEFORE THE INCLUDE MAKES IT COMPILE



struct Foo {
    unsigned int member; // MAKING THIS TYPE INT INSTEAD OF UNSIGNED INT MAKES IT COMPILE
};



void selectPhysicalDevice()
{
    //std::terminate(); // UNCOMMENTING THIS MAKES IT COMPILE


    Foo foo{};
    auto max_samplers = foo.member;

    String str;
    str.append(max_samplers); // COMMENTING THIS OUT MAKES IT COMPILE
    // REPLACING max_samplers WITH AN INTEGER LITERAL, ie., 1, MAKES IT COMPILE


    String str2;
    str2.append(1); // COMMENTING THIS OUT MAKES IT COMPILE

}





int main()
{


}

As you can see it makes absolutely no sense. I tried to compile this on a new version of MSVC and it compiles fine. It's interesting the error goes away when doing import BEFORE the includes on Clang, because I was told on GCC it's the other way around, the imports need to come AFTER the includes.