bug: Decorated property not supported

[thomedes]

When running mypy on a file with the following content:

class Foo:
    @property
    def bar(self):
        return 'baz'

    def bar(self):
        return 'baz'

It will crash with following traceback:

non-method-property.py:6: error: Decorated property not supported
non-method-property.py:2: error: INTERNAL ERROR -- please report a bug at https://github.com/python/mypy/issues version: 0.680+dev.2ef066fa651ac048d220c751a4f7554b949a2c13
Traceback (most recent call last):
  File "/usr/local/bin/mypy", line 11, in <module>
    load_entry_point('mypy==0.680+dev.2ef066fa651ac048d220c751a4f7554b949a2c13', 'console_scripts', 'mypy')()
  File "/usr/local/lib/python3.6/dist-packages/mypy/__main__.py", line 7, in console_entry
    main(None)
  File "/usr/local/lib/python3.6/dist-packages/mypy/main.py", line 91, in main
    res = build.build(sources, options, None, flush_errors, fscache)
  File "/usr/local/lib/python3.6/dist-packages/mypy/build.py", line 162, in build
    result = _build(sources, options, alt_lib_path, flush_errors, fscache)
  File "/usr/local/lib/python3.6/dist-packages/mypy/build.py", line 217, in _build
    graph = dispatch(sources, manager)
  File "/usr/local/lib/python3.6/dist-packages/mypy/build.py", line 2388, in dispatch
    process_graph(graph, manager)
  File "/usr/local/lib/python3.6/dist-packages/mypy/build.py", line 2693, in process_graph
    process_stale_scc(graph, scc, manager)
  File "/usr/local/lib/python3.6/dist-packages/mypy/build.py", line 2800, in process_stale_scc
    graph[id].type_check_first_pass()
  File "/usr/local/lib/python3.6/dist-packages/mypy/build.py", line 1947, in type_check_first_pass
    self.type_checker().check_first_pass()
  File "/usr/local/lib/python3.6/dist-packages/mypy/checker.py", line 282, in check_first_pass
    self.accept(d)
  File "/usr/local/lib/python3.6/dist-packages/mypy/checker.py", line 393, in accept
    stmt.accept(self)
  File "/usr/local/lib/python3.6/dist-packages/mypy/nodes.py", line 846, in accept
    return visitor.visit_class_def(self)
  File "/usr/local/lib/python3.6/dist-packages/mypy/checker.py", line 1535, in visit_class_def
    self.accept(defn.defs)
  File "/usr/local/lib/python3.6/dist-packages/mypy/checker.py", line 393, in accept
    stmt.accept(self)
  File "/usr/local/lib/python3.6/dist-packages/mypy/nodes.py", line 911, in accept
    return visitor.visit_block(self)
  File "/usr/local/lib/python3.6/dist-packages/mypy/checker.py", line 1701, in visit_block
    self.accept(s)
  File "/usr/local/lib/python3.6/dist-packages/mypy/checker.py", line 393, in accept
    stmt.accept(self)
  File "/usr/local/lib/python3.6/dist-packages/mypy/nodes.py", line 454, in accept
    return visitor.visit_overloaded_func_def(self)
  File "/usr/local/lib/python3.6/dist-packages/mypy/checker.py", line 426, in visit_overloaded_func_def
    self._visit_overloaded_func_def(defn)
  File "/usr/local/lib/python3.6/dist-packages/mypy/checker.py", line 441, in _visit_overloaded_func_def
    assert isinstance(fdef, Decorator)
AssertionError: 
non-method-property.py:2: : note: use --pdb to drop into pdb

I expected mypy to simply signal an error about reusing a method/property name.

Happening on both Ubuntu 18.04.1 LTS's apt install version and on latest version installed from GitHub. Python 3.6.7

[tirkarthi]

Related : #5561 and #1362

[ilevkivskyi]

Yes, we should just report an error instead of crashing.

[TH3CHARLie]

This crash no more occurs in master. Output:

test.py:2: error: Single overload definition, multiple required
test.py:6: error: Unexpected definition for property "bar"

[JelleZijlstra]

Seems like this issue can be closed then? Those errors look correct.

[TH3CHARLie]

Seems like this issue can be closed then? Those errors look correct.

I think it's OK to do so.

[frispete]

Yes, we should just report an error instead of crashing.

Hmm, so it is an error to use decorators with mypy?

The offending code for my case:

@functools.total_ordering
class ClassName:
    def __init__(self):
        """whatever"""

    @property
    @functools.lru_cache()
    def method(self):
         """expensive operation, that should show as property"""

[JelleZijlstra]

@frispete mypy supports decorators in general, but there may be specific patterns that aren't supported. This issue is about a specific problem that led to a crash (not just a mypy error), which is fixed; if you have a different problem involving decorators, feel free to open a new issue.