PP1006

Internal slot $Name modified in a nested context. This is not yet supported.

This error would typically only occur in an optimized function when an internal slot, as specified by the JavaScript spec, gets mutated in a conditional context.

This error indicates that you have hit a limitation in Prepack. Try to rearrange your code to overcome the limitation, or feel free to file an issue on GitHub with a feature request that a particular named internal slot should be supported.