### Compilation failed:

error: 3: invalid type
layout(binding=0) sampler2D s;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: 5: 'main' must return: 'vec4', 'float4', or 'half4'
void main() {
^^^^^^^^^^^
error: 6: unknown identifier 'sample'
    float4 a = sample(s, float2(0));
               ^^^^^^
error: 6: unknown identifier 's'
    float4 a = sample(s, float2(0));
                      ^
error: 7: unknown identifier 'sample'
    float4 b = sample(s, float3(0));
               ^^^^^^
error: 7: unknown identifier 's'
    float4 b = sample(s, float3(0));
                      ^
error: 8: unknown identifier 'sk_FragColor'
    sk_FragColor = half4(half2(a.xy), half2(b.xy));
    ^^^^^^^^^^^^
error: 8: unknown identifier 'a'
    sk_FragColor = half4(half2(a.xy), half2(b.xy));
                               ^
error: 8: unknown identifier 'b'
    sk_FragColor = half4(half2(a.xy), half2(b.xy));
                                            ^
9 errors