Bad global type in WGSL causes create_shader_module to panic, not return an error

[jimblandy]

If you call wgpu_core::Global::create_shader_module with WGSL that has a var<uniform> of type mat2x2<f32>, and an entry point that uses it, the module passes Naga validation, but wgpu_core::validation::Interface::new panics.

To reproduce:

use anyhow::Result; // anyhow = "1"
use futures_executor::block_on; // futures-executor = "0.3"

fn main() -> Result<()> {
    let instance = wgpu::Instance::new(wgpu::Backends::VULKAN);

    let (device, queue) = block_on(async {
        let adapter = instance.request_adapter(&wgpu::RequestAdapterOptions::default())
            .await
            .expect("request_adapter returned None");
        adapter.request_device(&wgpu::DeviceDescriptor {
            label: Some("play-wgpu device"),
            features: wgpu::Features::default(),
            limits: wgpu::Limits::default(),
        },
                               None).await
    })?;

    let module = device.create_shader_module(&wgpu::ShaderModuleDescriptor {
        label: Some("play-wgpu shader module"),
        source: wgpu::ShaderSource::Wgsl("
            @group(0) @binding(0) var<uniform> xform: mat2x2<f32>;
            @stage(compute) @workgroup_size(32) fn main() { let use_it = xform; }
        ".into())
    });

    drop((module, queue));

    Ok(())
}

Because xform has an unexpected type for a global, there is no entry created for it in Interface::new's resource_mapping table, and then trying to push the EntryPoint::resources entry for main's use of xform panics.

[jimblandy]

I think I know what happened here:

• The WebGPU committee recently made a change to WGSL to allow non-struct globals:
  Store type for buffer does not have to be structure gpuweb/gpuweb#2401
• And this change was implemented in Naga:
  Allow non-structure buffer types naga#1682
• But clearly wgpu_core::validation::Interface::new didn't get the memo, because it still expects only a limited set of types.