naga panic during translation

panic_shader.frag

#version 450 core

vec3 i_resolution;
vec4 i_mouse;
float i_time;
float i_time_delta;
int i_frame;

// Shadertoy compatibility, see we can use the same code copied from shadertoy website

#define iTime i_time
#define iResolution i_resolution
#define iTimeDelta i_time_delta
#define iMouse i_mouse
#define iFrame i_frame

#define mainImage shader_main
// step 1: a funciton with an inout input and some other return value
float fn(inout float a) {
    a += 0.1;
    return 0.2;
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    // step 2: first variable that is vec2/vec3 (float works)
    vec2 cd = vec2(0.3, 0.4);
    
    // step 3: second variable is assigned to the return value, using first variable as args.
    float e = fn(cd.x);
    
    // Output to screen
    fragColor = vec4(e);
}

layout(location = 0) in vec2 uv;

struct ShadertoyInput {
    vec4 mouse;
    vec3 resolution;
    float time;
    float time_delta;
    int frame;
};

layout(binding = 0) uniform ShadertoyInput input;
out vec4 FragColor;
void main(){

    i_time = input.time;
    i_resolution = input.resolution;
    i_time_delta = input.time_delta;
    i_mouse = input.mouse;
    i_frame = input.frame;


    vec2 uv = vec2(uv.x, 1.0 - uv.y);
    vec2 frag_coord = uv * i_resolution.xy;

    shader_main(FragColor, frag_coord);

}