(playground314) > py -V
Python 3.14.0b3

(playground314) > more x.py
t'{42}'

(playground314) > mypy x.py --show-traceback
x.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: 1.17.0+dev.16e99de5376464beaa2cf086c1cd3dc5d26a791a
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "<dir>\.venv\Scripts\mypy.exe\__main__.py", line 10, in <module>
    sys.exit(console_entry())
  File "<dir>\.venv\Lib\site-packages\mypy\__main__.py", line 15, in console_entry
    main()
  File "<dir>\.venv\Lib\site-packages\mypy\main.py", line 127, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
  File "<dir>\.venv\Lib\site-packages\mypy\main.py", line 211, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "<dir>\.venv\Lib\site-packages\mypy\build.py", line 191, in build
    result = _build(
  File "<dir>\.venv\Lib\site-packages\mypy\build.py", line 267, in _build
    graph = dispatch(sources, manager, stdout)
  File "<dir>\.venv\Lib\site-packages\mypy\build.py", line 2886, in dispatch
    graph = load_graph(sources, manager)
  File "<dir>\.venv\Lib\site-packages\mypy\build.py", line 3072, in load_graph
    st = State(
  File "<dir>\.venv\Lib\site-packages\mypy\build.py", line 1993, in __init__
    self.parse_file(temporary=temporary)
  File "<dir>\.venv\Lib\site-packages\mypy\build.py", line 2133, in parse_file
    with self.wrap_context():
  File "C:\Program Files\Python314\Lib\contextlib.py", line 162, in __exit__
    self.gen.throw(value)
  File "<dir>\.venv\Lib\site-packages\mypy\build.py", line 2062, in wrap_context
    yield
  File "<dir>\.venv\Lib\site-packages\mypy\build.py", line 2171, in parse_file
    self.tree = manager.parse_file(
                ~~~~~~~~~~~~~~~~~~^
        self.id,
        ^^^^^^^^
    ...<3 lines>...
        options=self.options,
        ^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "<dir>\.venv\Lib\site-packages\mypy\build.py", line 840, in parse_file
    tree = parse(source, path, id, self.errors, options=options)
  File "<dir>\.venv\Lib\site-packages\mypy\parse.py", line 27, in parse
    tree = mypy.fastparse.parse(source, fnam=fnam, module=module, errors=errors, options=options)
  File "<dir>\.venv\Lib\site-packages\mypy\fastparse.py", line 241, in parse
    ).visit(ast)
      ~~~~~^^^^^
  File "<dir>\.venv\Lib\site-packages\mypy\fastparse.py", line 435, in visit
    return visitor(node)
  File "<dir>\.venv\Lib\site-packages\mypy\fastparse.py", line 894, in visit_Module
    body = self.fix_function_overloads(self.translate_stmt_list(mod.body, ismodule=True))
                                       ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<dir>\.venv\Lib\site-packages\mypy\fastparse.py", line 509, in translate_stmt_list
    node = self.visit(stmt)
  File "<dir>\.venv\Lib\site-packages\mypy\fastparse.py", line 435, in visit
    return visitor(node)
  File "<dir>\.venv\Lib\site-packages\mypy\fastparse.py", line 1459, in visit_Expr
    value = self.visit(n.value)
  File "<dir>\.venv\Lib\site-packages\mypy\fastparse.py", line 432, in visit
    visitor = getattr(self, method)
AttributeError: 'ASTConverter' object has no attribute 'visit_TemplateStr'
x.py: : note: use --pdb to drop into pdb