gfx-rs/wgpu · error

not implemented

Error message

not implemented

What it means

Panic in naga's SPIR-V backend: Load::from_image_expr hit an image with ImageClass::External, which the Vulkan writer has no SPIR-V counterpart for (external images are Metal-only). The faulty input is a module using an external image while targeting SPIR-V.

Source

Thrown at naga/src/back/spv/image.rs:121

    type_id: Word,

    /// The id of the image being accessed.
    image_id: Word,
}

impl Load {
    fn from_image_expr(
        ctx: &mut BlockContext<'_>,
        image_id: Word,
        image_class: crate::ImageClass,
        result_type_id: Word,
    ) -> Result<Load, Error> {
        let opcode = match image_class {
            crate::ImageClass::Storage { .. } => spirv::Op::ImageRead,
            crate::ImageClass::Depth { .. } | crate::ImageClass::Sampled { .. } => {
                spirv::Op::ImageFetch
            }
            crate::ImageClass::External => unimplemented!(),
        };

        // `OpImageRead` and `OpImageFetch` instructions produce vec4<f32>
        // values. Most of the time, we can just use `result_type_id` for
        // this. The exception is that `Expression::ImageLoad` from a depth
        // image produces a scalar `f32`, so in that case we need to find
        // the right SPIR-V type for the access instruction here.
        let type_id = match image_class {
            crate::ImageClass::Depth { .. } => ctx.get_numeric_type_id(NumericType::Vector {
                size: crate::VectorSize::Quad,
                scalar: crate::Scalar::F32,
            }),
            _ => result_type_id,
        };

        Ok(Load {
            opcode,
            type_id,

View on GitHub (pinned to 3e11ff59bf)

Solutions

1. Do not use external textures/images when compiling shaders to SPIR-V
2. Target MSL when external images are required

When it happens

Trigger: Thrown at naga/src/back/spv/image.rs:121 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of gfx-rs/wgpu@3e11ff59bf (2026-09-03). Data as JSON: /api/errors/1d013042f782e4a2. Report an issue: GitHub.