nopython rewrites don't account for variables that should raise "NameError"

[stuartarchibald]

Reporting a bug

• I have tried using the latest released version of Numba (most recent is
  visible in the change log (https://github.com/numba/numba/blob/main/CHANGE_LOG).
• I have included a self contained code sample to reproduce the problem.
  i.e. it's possible to run as 'python bug.py'.

This:

from numba import njit

@njit('void(float64[::1],)')
def foo(out):
    for i in range(missing_definition1):
        while missing_definition2:
            out[i]

produces:

RuntimeError: liveness info missing for vars: {'i'}

from the nopython rewrites pass. The exception comes from here:

numba/numba/core/analysis.py

Lines 173 to 180 in e7a1e83

	if missing_vars:
	# There are no exit points
	if not cfg.exit_points():
	# We won't be able to verify this
	pass
	else:
	msg = 'liveness info missing for vars: {0}'.format(missing_vars)
	raise RuntimeError(msg)

It looks like that there's something wrong is identified, it's just that a more ICE-like error is raised than a NameError that would be expected by a user.