Throwing compilation errors

Using the error intrinsic, you can cause a compilation error with a message:

if (gi_quality == only_ao) {
// ..
} else if (gi_quality == high) {
  // ..
} else {
  error("Unimplemented gi quality");
}

Compiler output:

[ERROR] ../../../prog/gameLibs/render/shaders/debugGbuffer.dshl(41,9): "Unimplemented gi quality"