AttributeError: 'ASTConverter' object has no attribute 'visit_TypeAlias' and Python 3.12.0rc1

[ChrisGojlo]

Crash Report

mypy crashes when a non-generic type alias is used
https://peps.python.org/pep-0695/#generic-type-alias

Traceback

mypy --show-traceback scratchpad.py                                               
scratchpad.py: error: INTERNAL ERROR -- Please try using mypy master on GitHub:
https://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 1.7.0+dev.d440490270b643b2be333b5b27b154813f016ab6
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.12/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/__main__.py", line 15, in console_entry
    main()
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/main.py", line 99, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/main.py", line 178, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/build.py", line 189, in build
    result = _build(
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/build.py", line 262, in _build
    graph = dispatch(sources, manager, stdout)
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/build.py", line 2885, in dispatch
    graph = load_graph(sources, manager)
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/build.py", line 3071, in load_graph
    st = State(
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/build.py", line 1994, in __init__
    self.parse_file()
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/build.py", line 2134, in parse_file
    with self.wrap_context():
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/contextlib.py", line 155, in __exit__
    self.gen.throw(value)
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/build.py", line 2063, in wrap_context
    yield
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/build.py", line 2170, in parse_file
    self.tree = manager.parse_file(
                ^^^^^^^^^^^^^^^^^^^
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/build.py", line 835, in parse_file
    tree = parse(source, path, id, self.errors, options=options)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/parse.py", line 22, in parse
    return mypy.fastparse.parse(source, fnam=fnam, module=module, errors=errors, options=options)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/fastparse.py", line 228, in parse
    ).visit(ast)
      ^^^^^^^^^^
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/fastparse.py", line 397, in visit
    return visitor(node)
           ^^^^^^^^^^^^^
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/fastparse.py", line 856, in visit_Module
    body = self.fix_function_overloads(self.translate_stmt_list(mod.body, ismodule=True))
                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/fastparse.py", line 471, in translate_stmt_list
    node = self.visit(stmt)
           ^^^^^^^^^^^^^^^^
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/site-packages/mypy/fastparse.py", line 395, in visit
    visitor = getattr(self, method)
              ^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'ASTConverter' object has no attribute 'visit_TypeAlias'

To Reproduce

scratchpad.py

type A = str
def myf(arg1: A):
    return arg1

x = myf("hello")
print(x)

Your Environment

• Mypy version used: 1.7.0+dev.d440490270b643b2be333b5b27b154813f016ab6
• Mypy command-line flags: --show-traceback
• Mypy configuration options from mypy.ini (and other config files):None
• Python version used: 3.12.0rc1
• Operating system and version: macOS 13.5.1 (22G90)

[hauntsaninja]

mypy doesn't yet support PEP 695. I'll make this have a better error in the meantime though. Closing as duplicate of #15238

[dibrinsofor]

I still encounter this, was this ever addressed?

[hauntsaninja]

you're almost certainly on some ancient mypy version. maybe spend a minute to look at the issue before posting?