newsemanal crash with dataclasses

[JelleZijlstra]

This file:

from dataclasses import dataclass


@dataclass
class Function:
    function: str
    args: object

    def __init__(self, function: str, *args: object) -> None:
        self.function = function
        self.args = args


Function("x", 1, 2)

Crashes on 0.701 with:

$ mypy --new-semantic-analyzer dataclassinit.py 
dataclassinit.py: error: INTERNAL ERROR -- please report a bug at https://github.com/python/mypy/issues version: 0.701
Traceback (most recent call last):
  File "/home/jelle/ans/venv/bin/mypy", line 10, in <module>
    sys.exit(console_entry())
  File "/home/jelle/ans/venv/lib/python3.6/site-packages/mypy/__main__.py", line 7, in console_entry
    main(None)
  File "mypy/build.py", line 1767, in __mypyc_generator_helper__
  File "mypy/newsemanal/semanal_main.py", line 294, in check_type_arguments
  File "mypy/nodes.py", line 273, in accept
  File "mypy/newsemanal/semanal_typeargs.py", line 27, in visit_mypy_file__NodeVisitor_glue
  File "mypy/newsemanal/semanal_typeargs.py", line 30, in visit_mypy_file
  File "mypy/traverser.py", line 33, in visit_mypy_file
  File "mypy/nodes.py", line 896, in accept
  File "mypy/newsemanal/semanal_typeargs.py", line 39, in visit_class_def__StatementVisitor_glue
  File "mypy/newsemanal/semanal_typeargs.py", line 41, in visit_class_def
  File "mypy/mixedtraverser.py", line 28, in visit_class_def
  File "mypy/traverser.py", line 65, in visit_class_def
  File "mypy/nodes.py", line 961, in accept
  File "mypy/newsemanal/semanal_typeargs.py", line 43, in visit_block__StatementVisitor_glue
  File "mypy/newsemanal/semanal_typeargs.py", line 45, in visit_block
  File "mypy/traverser.py", line 37, in visit_block
  File "mypy/nodes.py", line 641, in accept
  File "mypy/traverser.py", line 51, in visit_func_def__StatementVisitor_glue
  File "mypy/traverser.py", line 52, in visit_func_def
  File "mypy/newsemanal/semanal_typeargs.py", line 33, in visit_func__MixedTraverserVisitor_glue
  File "mypy/newsemanal/semanal_typeargs.py", line 37, in visit_func
  File "mypy/mixedtraverser.py", line 23, in visit_func
  File "mypy/mixedtraverser.py", line 90, in visit_optional_type
  File "mypy/types.py", line 934, in accept
  File "mypy/typetraverser.py", line 48, in visit_callable_type__TypeVisitor_glue
  File "mypy/typetraverser.py", line 52, in visit_callable_type
  File "mypy/types.py", line 625, in accept
  File "mypy/newsemanal/semanal_typeargs.py", line 47, in visit_instance__TypeVisitor_glue
  File "mypy/newsemanal/semanal_typeargs.py", line 51, in visit_instance
AttributeError: attribute 'defn' of 'TypeInfo' undefined
dataclassinit.py: : note: use --pdb to drop into pdb

And on master with:

$ mypy --new-semantic-analyzer dataclassinit.py 
dataclassinit.py: error: INTERNAL ERROR -- please report a bug at https://github.com/python/mypy/issues version: 0.710+dev.aec4f2affc50664ce618acc2d74b34bd0961818d
Traceback (most recent call last):
  File "/home/jelle/repos/mypy/.venv/bin/mypy", line 11, in <module>
    load_entry_point('mypy', 'console_scripts', 'mypy')()
  File "/home/jelle/repos/mypy/mypy/__main__.py", line 7, in console_entry
    main(None)
  File "/home/jelle/repos/mypy/mypy/main.py", line 85, in main
    res = build.build(sources, options, None, flush_errors, fscache)
  File "/home/jelle/repos/mypy/mypy/build.py", line 163, in build
    result = _build(sources, options, alt_lib_path, flush_errors, fscache)
  File "/home/jelle/repos/mypy/mypy/build.py", line 219, in _build
    graph = dispatch(sources, manager)
  File "/home/jelle/repos/mypy/mypy/build.py", line 2462, in dispatch
    process_graph(graph, manager)
  File "/home/jelle/repos/mypy/mypy/build.py", line 2765, in process_graph
    process_stale_scc(graph, scc, manager)
  File "/home/jelle/repos/mypy/mypy/build.py", line 2863, in process_stale_scc
    semantic_analysis_for_scc(graph, scc, manager.errors)
  File "/home/jelle/repos/mypy/mypy/newsemanal/semanal_main.py", line 79, in semantic_analysis_for_scc
    check_type_arguments(graph, scc, errors)
  File "/home/jelle/repos/mypy/mypy/newsemanal/semanal_main.py", line 307, in check_type_arguments
    state.tree.accept(analyzer)
  File "/home/jelle/ans/venv/lib/python3.6/contextlib.py", line 99, in __exit__
    self.gen.throw(type, value, traceback)
  File "/home/jelle/repos/mypy/mypy/build.py", line 1768, in wrap_context
    yield
  File "/home/jelle/repos/mypy/mypy/newsemanal/semanal_main.py", line 307, in check_type_arguments
    state.tree.accept(analyzer)
  File "/home/jelle/repos/mypy/mypy/nodes.py", line 275, in accept
    return visitor.visit_mypy_file(self)
  File "/home/jelle/repos/mypy/mypy/newsemanal/semanal_typeargs.py", line 33, in visit_mypy_file
    super().visit_mypy_file(o)
  File "/home/jelle/repos/mypy/mypy/traverser.py", line 33, in visit_mypy_file
    d.accept(self)
  File "/home/jelle/repos/mypy/mypy/nodes.py", line 901, in accept
    return visitor.visit_class_def(self)
  File "/home/jelle/repos/mypy/mypy/newsemanal/semanal_typeargs.py", line 44, in visit_class_def
    super().visit_class_def(defn)
  File "/home/jelle/repos/mypy/mypy/mixedtraverser.py", line 28, in visit_class_def
    super().visit_class_def(o)
  File "/home/jelle/repos/mypy/mypy/traverser.py", line 65, in visit_class_def
    o.defs.accept(self)
  File "/home/jelle/repos/mypy/mypy/nodes.py", line 966, in accept
    return visitor.visit_block(self)
  File "/home/jelle/repos/mypy/mypy/newsemanal/semanal_typeargs.py", line 48, in visit_block
    super().visit_block(o)
  File "/home/jelle/repos/mypy/mypy/traverser.py", line 37, in visit_block
    s.accept(self)
  File "/home/jelle/repos/mypy/mypy/nodes.py", line 643, in accept
    return visitor.visit_func_def(self)
  File "/home/jelle/repos/mypy/mypy/traverser.py", line 52, in visit_func_def
    self.visit_func(o)
  File "/home/jelle/repos/mypy/mypy/newsemanal/semanal_typeargs.py", line 40, in visit_func
    super().visit_func(defn)
  File "/home/jelle/repos/mypy/mypy/mixedtraverser.py", line 23, in visit_func
    self.visit_optional_type(o.type)
  File "/home/jelle/repos/mypy/mypy/mixedtraverser.py", line 91, in visit_optional_type
    t.accept(self)
  File "/home/jelle/repos/mypy/mypy/types.py", line 939, in accept
    return visitor.visit_callable_type(self)
  File "/home/jelle/repos/mypy/mypy/typetraverser.py", line 52, in visit_callable_type
    t.fallback.accept(self)
  File "/home/jelle/repos/mypy/mypy/types.py", line 630, in accept
    return visitor.visit_instance(self)
  File "/home/jelle/repos/mypy/mypy/newsemanal/semanal_typeargs.py", line 54, in visit_instance
    for (i, arg), tvar in zip(enumerate(t.args), info.defn.type_vars):
  File "/home/jelle/repos/mypy/mypy/nodes.py", line 2588, in __getattribute__
    raise AssertionError(object.__getattribute__(self, 'msg'))
AssertionError: fallback can't be filled out until semanal
dataclassinit.py: : note: use --pdb to drop into pdb

[ilevkivskyi]

This is essentially a duplicate of #6454. The cause is the duplicate definitions of __init__ (one user defined and one generated). The best fix for now is probably to just use the -redefinition hack (the first bullet point in Jukka's comment). Note that there is also another test case that crashes because of this [case testNewNamedTupleIllegalNames].

Maybe we can move this to the original issue and close this one? Or maybe vice-versa?

[JelleZijlstra]

Thanks! Let's just close this and I'll leave a comment on the original issue.