Stubgen crashes on dataclass field

[KapJI]

Crash Report

When running stubgen on home assistant codebase on the latest master, it crashes with the following error.

Traceback

Traceback (most recent call last):
  File ".venv/bin/stubgen", line 10, in <module>
    sys.exit(main())
             ~~~~^^
  File ".venv/lib/python3.13/site-packages/mypy/stubgen.py", line 1984, in main
    generate_stubs(options)
    ~~~~~~~~~~~~~~^^^^^^^^^
  File ".venv/lib/python3.13/site-packages/mypy/stubgen.py", line 1787, in generate_stubs
    generate_stub_for_py_module(
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~^
        mod,
        ^^^^
    ...<7 lines>...
        all_modules=all_module_names,
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File ".venv/lib/python3.13/site-packages/mypy/stubgen.py", line 1757, in generate_stub_for_py_module
    mod.ast.accept(gen)
    ~~~~~~~~~~~~~~^^^^^
  File ".venv/lib/python3.13/site-packages/mypy/nodes.py", line 361, in accept
    return visitor.visit_mypy_file(self)
           ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File ".venv/lib/python3.13/site-packages/mypy/stubgen.py", line 504, in visit_mypy_file
    super().visit_mypy_file(o)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^
  File ".venv/lib/python3.13/site-packages/mypy/traverser.py", line 119, in visit_mypy_file
    d.accept(self)
    ~~~~~~~~^^^^^^
  File ".venv/lib/python3.13/site-packages/mypy/nodes.py", line 1200, in accept
    return visitor.visit_class_def(self)
           ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File ".venv/lib/python3.13/site-packages/mypy/stubgen.py", line 811, in visit_class_def
    super().visit_class_def(o)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^
  File ".venv/lib/python3.13/site-packages/mypy/traverser.py", line 155, in visit_class_def
    o.defs.accept(self)
    ~~~~~~~~~~~~~^^^^^^
  File ".venv/lib/python3.13/site-packages/mypy/nodes.py", line 1281, in accept
    return visitor.visit_block(self)
           ~~~~~~~~~~~~~~~~~~~^^^^^^
  File ".venv/lib/python3.13/site-packages/mypy/stubgen.py", line 906, in visit_block
    super().visit_block(o)
    ~~~~~~~~~~~~~~~~~~~^^^
  File ".venv/lib/python3.13/site-packages/mypy/traverser.py", line 123, in visit_block
    s.accept(self)
    ~~~~~~~~^^^^^^
  File ".venv/lib/python3.13/site-packages/mypy/nodes.py", line 1368, in accept
    return visitor.visit_assignment_stmt(self)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File ".venv/lib/python3.13/site-packages/mypy/stubgen.py", line 943, in visit_assignment_stmt
    init = self.get_init(item.name, o.rvalue, annotation)
  File ".venv/lib/python3.13/site-packages/mypy/stubgen.py", line 1254, in get_init
    initializer = self.get_assign_initializer(rvalue)
  File ".venv/lib/python3.13/site-packages/mypy/stubgen.py", line 1275, in get_assign_initializer
    return f" = {rvalue.accept(p)}"
                 ~~~~~~~~~~~~~^^^
  File ".venv/lib/python3.13/site-packages/mypy/nodes.py", line 1990, in accept
    return visitor.visit_call_expr(self)
           ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File ".venv/lib/python3.13/site-packages/mypy/stubgen.py", line 296, in visit_call_expr
    args.append(f"{name}={arg.accept(self)}")
                          ~~~~~~~~~~^^^^^^
  File ".venv/lib/python3.13/site-packages/mypy/nodes.py", line 2071, in accept
    return visitor.visit_unary_expr(self)
           ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File ".venv/lib/python3.13/site-packages/mypy/visitor.py", line 527, in visit_unary_expr
    raise NotImplementedError()
NotImplementedError

To Reproduce

from dataclasses import dataclass, field

@dataclass
class ClassName:
    field_name: float = field(default=-1, init=False)

Your Environment

• Mypy version used: 67b70ce00ee9f2da1c49e75a044aad7ab7c137ff
• Mypy command-line flags: stubgen test.py
• Mypy configuration options from mypy.ini (and other config files):
• Python version used: 3.13.2
• Operating system and version: Linux, MacOS

[KapJI]

cc @cdce8p In case you are interested.

[sterliakov]

This is just a simple visitor method missing, will fix today. There are other missing methods (dicts/lists/tuples are handled, while sets are not, for example), let's try to add a few more.