The type system error is fixed in #5945.

However the code your provide contains an invalid use of pointers. Taking an address of a structured buffer element is not something we can support, and will result in invalid SPIRV. Slang currently only support pointers to memory in PhysicalStorageBuffer space, but structured buffers are in StorageBuffer address space, so forming a pointer to such elements shouldn't be allowed, and we need to add diagnostics to prevent user from doing so.

To pass a reference to an Atomic<T> object to a different function, you can use __ref parameter direction:

module "test_module";

public void atomicFunc(__ref Atomic<int> ptr) {
    ptr.add(1);
}

import "test_module";

RWStructuredBuffer<Atomic<int>> input0;

[shader("compute")]
[numthreads(1,1,1)]
void computeMain(uint3 workGroup : SV_GroupID)
{
    atomicFunc(input0[0]);
}

Thank you for the quick response.

This invalid pointer usage was introduced when looking for a minimal reproducible example from my original source code (in which I use PhysicalStorageBuffer), I apologize for that.

Usage of __ref is more straightforward in any case, I didn't know about it. Is it documented anywhere?

This is not yet documented because it hasn't been tested in user code enough, and the way we support it today on spirv is still via inlining. We will document it for public use once we can generate real pointer code in SPIRV with future extensions and confirm it is stable enough. Before that it will continue to be internal/experimental feature.