numba: Operation "element in set" never returns

Bug: After a series of add and remove operations on a set in nopython mode the operation “in set” does not return and gets stuck at 100% CPU load.

Isolated code example:

import numba as nb

@ nb.njit()
def problem():

    # init
    openSet = set()

    openSet.add((0, 0))
    openSet.add((1, 0))
    openSet.add((2, 0))
    openSet.add((3, 0))
    openSet.add((4, 0))
    openSet.add((5, 0))
    openSet.add((6, 0))
    openSet.add((7, 0))
    openSet.add((8, 0))

    openSet.remove((2, 0))
    openSet.add((2, 1))
    openSet.remove((2, 1))
    openSet.remove((4, 0))
    openSet.add((5, 1))
    openSet.add((4, 1))
    openSet.remove((7, 0))
    openSet.add((8, 1))
    openSet.add((7, 1))
    openSet.add((6, 1))
    openSet.remove((8, 0))
    openSet.remove((1, 0))
    openSet.remove((0, 0))
    openSet.remove((5, 0))
    openSet.remove((6, 0))
    openSet.remove((3, 0))
    openSet.remove((7, 1))
    openSet.add((8, 2))
    openSet.add((7, 2))
    openSet.add((6, 2))
    openSet.remove((8, 1))
    openSet.remove((6, 1))
    openSet.add((5, 2))
    openSet.remove((4, 1))
    openSet.add((4, 2))
    openSet.remove((5, 1))
    openSet.remove((6, 2))
    openSet.add((7, 3))
    openSet.add((6, 3))
    openSet.add((5, 3))
    openSet.remove((7, 2))
    openSet.add((8, 3))
    openSet.remove((8, 2))
    openSet.remove((4, 2))
    openSet.add((4, 3))
    openSet.add((3, 3))
    openSet.remove((5, 2))
    openSet.remove((7, 3))
    openSet.add((8, 4))
    openSet.add((7, 4))
    print('About to check (6,4) in openSet')
    return (6, 4) in openSet


if __name__ == "__main__":
    print(problem())
    print('DONE')

The code gets stuck with numba 0.52.0 with Python 3.8.5 on Ubuntu 20.04.1 LTS x86_64.

However, @esc on gitter.im also confirmed that the issue persists on OSX.

Isolated code example: https://github.com/icezyclon/astart-pathfinding/blob/main/isolated.py Original code example (from A* search): https://github.com/icezyclon/astart-pathfinding/blob/main/problem.py