from dataclasses import dataclass, field

@dataclass(frozen=True)
class Demo:
    @property
    def c(self) -> int:
        return self.a + self.b

    a:int
    b:int
    
    c:int = field(init=False, default = c )
    

dataclass_mypy.py:13: error: Name 'c' already defined on line 6
dataclass_mypy.py:4: error: INTERNAL ERROR -- Please try using mypy master on Github:
https://mypy.rtfd.io/en/latest/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 0.740
Traceback (most recent call last):
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\runpy.py", line 192, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "C:\Users\HL167RR\AppData\Local\Programs\Python\Python38-32\Scripts\mypy.exe\__main__.py", line 9, in <module>
    sys.exit(console_entry())
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\__main__.py", line 8, in console_entry
    main(None, sys.stdout, sys.stderr)
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\main.py", line 88, in main
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\build.py", line 164, in build
    result = _build(sources, options, alt_lib_path, flush_errors, fscache, stdout, stderr)
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\build.py", line 229, in _build
    graph = dispatch(sources, manager, stdout)
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\build.py", line 2566, in dispatch
    process_graph(graph, manager)
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\build.py", line 2875, in process_graph
    process_stale_scc(graph, scc, manager)
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\build.py", line 2968, in process_stale_scc
    mypy.semanal_main.semantic_analysis_for_scc(graph, scc, manager.errors)
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\semanal_main.py", line 77, in semantic_analysis_for_scc
    process_top_levels(graph, scc, patches)
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\semanal_main.py", line 198, in process_top_levels
    deferred, incomplete, progress = semantic_analyze_target(next_id, state,
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\semanal_main.py", line 325, in semantic_analyze_target
    analyzer.refresh_partial(refresh_node,
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\semanal.py", line 378, in refresh_partial
    self.refresh_top_level(node)
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\semanal.py", line 389, in refresh_top_level
    self.accept(d)
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\semanal.py", line 4626, in accept
    node.accept(self)
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\nodes.py", line 927, in accept
    return visitor.visit_class_def(self)
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\semanal.py", line 1022, in visit_class_def
    self.analyze_class(defn)
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\semanal.py", line 1093, in analyze_class
    self.analyze_class_body_common(defn)
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\semanal.py", line 1102, in analyze_class_body_common
    self.apply_class_plugin_hooks(defn)
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\semanal.py", line 1148, in apply_class_plugin_hooks
    hook(ClassDefContext(defn, decorator, self))
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\plugins\dataclasses.py", line 367, in dataclass_class_maker_callback
    transformer.transform()
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\plugins\dataclasses.py", line 79, in transform
    attributes = self.collect_attributes()
  File "c:\users\hl167rr\appdata\local\programs\python\python38-32\lib\site-packages\mypy\plugins\dataclasses.py", line 240, in collect_attributes
    assert isinstance(node, Var)
AssertionError:
dataclass_mypy.py:4: : note: use --pdb to drop into pdb