Usage of Buffer and RWBuffer yields invalid WGSL code with no errors

[aleino-nv]

From discord issue 'Oddity With Buffers When Targeting Wgsl in 2025.3.2'.

The following code

Buffer<float> InputTyped;
RWBuffer<float> OutputTyped;

[numthreads(64, 1, 1)]
void Main(uint3 DTid : SV_DispatchThreadID)
{
    OutputTyped[DTid.x] = InputTyped[DTid.x];
}

Compiling with .\slangc .\test.slang -target wgsl -entry Main -stage compute -o test.txt produces invalid WGSL without any errors:

@compute
@workgroup_size(64, 1, 1)
fn Main(@builtin(global_invocation_id) DTid_0 : vec3<u32>)
{
}

[aleino-nv]

gpuweb/gpuweb#162

https://www.w3.org/TR/WGSL/#resource-interface

@csyonghe We should be emitting an error when Buffer and RWBuffer is used when targeting WGSL, right? As far as I can tell, WebGPU doesn't support either of these use-cases.

[csyonghe]

I agree. Using Buffer on wgsl should be an error.

[aleino-nv]

I agree. Using Buffer on wgsl should be an error.

@csyonghe Can we (should we?) use the capability system to raise this error?
(I've only seen examples where we use the capability system to constrain use of functions, rather than types, so I'm not sure how this would look. Any examples?)

[csyonghe]

Yes, this is exactly what the capability system is supposed to do. However we only implemented capability check in function calls and not on the type itself. For now let’s just mark the capability requirement on the Buffer type, and once the capability system is fully checking use sites of types we will get the error.