PP0014

for of loops over unknown collections are not yet supported

The collection value that the for of loop is iterating over is an unknown value. In general, analyzing the loop body to determine the effects the loop has on the heap is very complicated and makes the rest of the analysis lose precision. Therefore this is not yet supported.

To work around this limitation, consider changing the environment model so that the collection value expression is known to Prepack. Alternatively, the entire loop can be placed inside a __residual section (but only if the loop has no effect on the heap visible to Prepack).