### Compilation failed:

error: 2: unknown identifier 'sk_SampleMaskIn'
    return half4(sk_SampleMaskIn);
                 ^^^^^^^^^^^^^^^
error: 6: unknown identifier 'sk_SampleMask'
    sk_SampleMask = 0;
    ^^^^^^^^^^^^^
error: 10: unknown identifier 'sk_SampleMask'
    sk_SampleMask = sk_SampleMaskIn;
    ^^^^^^^^^^^^^
error: 10: unknown identifier 'sk_SampleMaskIn'
    sk_SampleMask = sk_SampleMaskIn;
                    ^^^^^^^^^^^^^^^
error: 13: 'main' must return: 'vec4', 'float4', or 'half4'
void main() {
^^^^^^^^^^^
error: 16: unknown identifier 'sk_SampleMask'
    sk_SampleMask = 0xFFFFFFFF;
    ^^^^^^^^^^^^^
error: 17: unknown identifier 'sk_FragColor'
    sk_FragColor = samplemaskin_as_color() / 256.0;
    ^^^^^^^^^^^^
7 errors