struct <fun>Output conflicts with fn <fun> on Metal

[Jengamon]

Description
Naga fails to rename a shader variable named "vsOutput", causing failures in shaders that use the name.

Repro steps
(at least, this works on latest MacOS, and does not repro on WASM)
(taken from https://webgpufundamentals.org/webgpu/lessons/webgpu-inter-stage-variables.html)

struct VertexOutput {
    @builtin(position) position: vec4f,
    @location(0) color: vec4f,
};

@vertex fn vs(
    @builtin(vertex_index) vertexIndex : u32
) -> VertexOutput {
    var pos = array(
        vec2f( 0.0,  0.5), // top center
        vec2f(-0.5, -0.5), // bottom left
        vec2f( 0.5, -0.5)  // bottom right
    );
    var color = array<vec4f, 3>(
        vec4f(1, 0, 0, 1), // red
        vec4f(0, 1, 0, 1), // green
        vec4f(0, 0, 1, 1), // blue
    );

    var vsOutput: VertexOutput;
    vsOutput.position = vec4f(pos[vertexIndex], 0.0, 1.0);
    vsOutput.color = color[vertexIndex];
    return vsOutput;
}

@fragment fn fs(fsInput: VertexOutput) -> @location(0) vec4f {
    return fsInput.color;
}

1. setup a program using the above shader
2. attempt to run the program and observe the crash

Expected vs observed behavior
Expected for the shader to compile and run.

Observed an error due to invalid types in shader.

Extra materials
cwfitzgerald told me to make this issue so here I am.

Platform
OS: MacOS 15.0.1
wgpu: 22.1.0

[Jengamon]

After a bit more investigation, I've found that the actual thing problematic variable name is <function name>Output, and vsOutput is only problematic inside a function named vs (vsyOutput is problematic in function vsy, etc.)

[ErichDonGubler]

Literally just barely solved this in #6438. 🙌🏻😤

Also, welcome the community! Thanks for taking the time to file. 🙂