### Compilation failed:

error: 11: index -1 out of range for 'float3x3'
    float3 undefined = indexMatrix(-1) + indexMatrix(3);
                                   ^^
error: 11: index 3 out of range for 'float3x3'
    float3 undefined = indexMatrix(-1) + indexMatrix(3);
                                                     ^
2 errors
