Fold fusion limitations clarification

[eddiemundo]

In the docs (https://streamly.composewell.com/haddocks/streamly-core-0.2.2/Streamly-Data-Fold.html) it says

Fusion Limitations

Folds support stream fusion for generating loops comparable to the speed of C. However, it has some limitations. For fusion to work, the folds must be inlined, folds must be statically known and not generated dynamically, folds should not be passed recursively.

What does "folds must be inlined" mean? Does that mean we have to use inline pragmas, or something else?

[eddiemundo]

In the docs it does say sometimes you do need to use different inline pragmas in different situations.