CrossHair dies on arguments with PEP604 Unions (e.g. "int|str")

[pschanely]

We expect a counterexample of "hi" here, but get an error instead.

There may be some related issues around these unions; note that typing_inspect does not yet understand them: https://github.com/ilevkivskyi/typing_inspect/pull/83

(ch_310) phillips-air:~ pschanely$ python -V
Python 3.10.0
(ch_310) phillips-air:~ pschanely$ cat foo.py
from typing import Union

def either(thing: (int|str)) -> (int|str):
    '''
    post: __return__ != "hi"
    '''
    return thing
(ch_310) phillips-air:~ pschanely$ crosshair check foo.py
Traceback (most recent call last):
  File "/Users/pschanely/miniconda3/envs/ch_310/bin/crosshair", line 33, in <module>
    sys.exit(load_entry_point('crosshair-tool', 'console_scripts', 'crosshair')())
  File "/Users/pschanely/proj/CrossHair/crosshair/main.py", line 658, in main
    sys.exit(unwalled_main(cmd_args))
  File "/Users/pschanely/proj/CrossHair/crosshair/main.py", line 608, in unwalled_main
    return check(args, options, sys.stdout, sys.stderr)
  File "/Users/pschanely/proj/CrossHair/crosshair/main.py", line 581, in check
    for message in run_checkables(analyze_any(entity, options)):
  File "/Users/pschanely/proj/CrossHair/crosshair/core.py", line 708, in run_checkables
    collector.extend(checkable.analyze())
  File "/Users/pschanely/proj/CrossHair/crosshair/core.py", line 639, in analyze
    analysis = analyze_calltree(options, conditions)
  File "/Users/pschanely/proj/CrossHair/crosshair/core.py", line 980, in analyze_calltree
    call_analysis = attempt_call(
  File "/Users/pschanely/proj/CrossHair/crosshair/core.py", line 1188, in attempt_call
    bound_args = gen_args(conditions.sig) if bound_args is None else bound_args
  File "/Users/pschanely/proj/CrossHair/crosshair/core.py", line 586, in gen_args
    value = proxy_for_type(param.annotation, smt_name, allow_subtypes)
  File "/Users/pschanely/proj/CrossHair/crosshair/core.py", line 549, in proxy_for_type
    return proxy_for_class(typ, varname)
  File "/Users/pschanely/proj/CrossHair/crosshair/core.py", line 388, in proxy_for_class
    data_members = get_type_hints(typ)
  File "/Users/pschanely/miniconda3/envs/ch_310/lib/python3.10/typing.py", line 1827, in get_type_hints
    raise TypeError('{!r} is not a module, class, method, '
TypeError: int | str is not a module, class, method, or function.