Why image sample inside compute shader is invalid?

[jj11hh]

@group(0) @binding(0) var src: texture_2d<f32>;
@group(0) @binding(1) var src_sampler: sampler;
@group(0) @binding(2) var dest: texture_storage_2d<rgba8unorm, read_write>;

const TILE_SIZE :f32 = 256.0;

@compute @workgroup_size(8, 8, 1)
fn init(@builtin(global_invocation_id) invocation_id: vec3<u32>, @builtin(num_workgroups) num_workgroups: vec3<u32>) {
    let location = vec2<i32>(i32(invocation_id.x), i32(invocation_id.y));
    let coord = vec2<f32>( (f32(invocation_id.x) + 0.5) / TILE_SIZE, (f32(invocation_id.y) + 0.5) / TILE_SIZE);
    let color = textureSample(src, src_sampler, coord);
    textureStore(dest, location, color);
}

The shader above just doesn't compile with naga, the error message is below:

�[2m2024-03-09T17:57:14.903161Z�[0m �[35mTRACE�[0m �[2mnaga_oil::compose::error�[0m�[2m:�[0m source offset: 0
�[2m2024-03-09T17:57:14.903353Z�[0m �[31mERROR�[0m �[2mbevy_render::render_resource::pipeline_cache�[0m�[2m:�[0m failed to process shader:
�[0m�[1m�[38;5;9merror�[0m�[1m: failed to build a valid final module: Entry point init at Compute is invalid�[0m
 �[0m�[36m=�[0m Uses operations forbidden at this stage

Is this a designed behavior or just a bug?

[ltxitai]

According to WGSL reference textureSample can only be used in fragment shaders: https://www.w3.org/TR/WGSL/#texturesample
You can use textureLoad in compute shaders: https://www.w3.org/TR/WGSL/#textureload

As for the reasons - I don't know. Probably better to ask over at https://github.com/gpuweb/gpuweb

[jj11hh]

Thanks, after reading the code of naga, I find only textureSampleLevel is allowed in compute shader. The reason may be textureSample will use auto mipmap level which cannot be determined in compute shader.