Sebastian Graf authored Sep 10, 2021 and Marge Bot committed Sep 11, 2021

Judging from the Assumption, we should never call `roundingMode#` on a negative
number. Yet the strange "dummy" conversion from `IN` to `IP` and the following
recursive call where making the function recursive.

Replacing the call by a panic makes `roundingMode#` non-recursive, so that we
may be able to inline it.

Fixes #20352.

It seems we trigger #19414 on some jobs, hence

Metric Decrease:
    T12545