MyPy fails on Python 3.14 PEP 750 template string (tstring, t-string), e.g. t'{42}' #19329
Description
Crash Report
MyPy (PyPI version and latest master from GitHub) fails on Python 3.14 PEP 750 template strings, e.g. t'{42}'.
I guess this is work in progress, while MyPy catches up with CPython. An error message like "MyPy doesn't support template strings yet" would be user friendlier. Therefore, and as requested ("Please report a bug"), creating this issue.
Traceback
(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
To Reproduce
Run mypy x.py with x.py containing f'{42}'.
Your Environment
- Mypy version used: GitHub master 1.17.0+dev
- Mypy command-line flags: None
- Mypy configuration options from
mypy.ini(and other config files): None - Python version used: 3.14.0b3 in virtual environment
.venv - Operating system and version: Windows 11