According to WebGPU's steps for createSampler, a GPUSampler's [[isFiltering]] internal slot should be true if GPUSamplerDescriptor's mipMapFilter member is "linear". I believe wgpu_core::resource::Sampler::filtering is the wgpu-core analog of [[isFiltering]], but the code to initialize it reads:

            filtering: desc.min_filter == wgt::FilterMode::Linear
                || desc.mag_filter == wgt::FilterMode::Linear,

I think this should also consider desc.mipmap_filter.