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Forward References under attrs classes extending Generic breaks mypy #5864
Description
System information:
$ python3 --version
Python 3.7.0
$ mypy --version
mypy 0.650+dev.0b61e5476520c6e2b8d0136fab645cb3414e412f
Minimal[-ish] example:
# mypy_break.py
import typing
from typing import Generic, Mapping, Union
import attr
T = typing.TypeVar('T', str, int)
@attr.s
class Klass(Generic[T], object):
modified = attr.ib(type=Mapping[T, 'UnionAlias'])
UnionAlias = Union[str, int]$ mypy mypy_break.py --show-traceback
mypy_break.py:7: error: INTERNAL ERROR -- please report a bug at https://github.com/python/mypy/issues version: 0.650+dev.0b61e5476520c6e2b8d0136fab645cb3414e412f
Traceback (most recent call last):
File "/usr/local/bin/mypy", line 11, in <module>
sys.exit(console_entry())
File "/usr/local/lib/python3.7/site-packages/mypy/__main__.py", line 7, in console_entry
main(None)
File "/usr/local/lib/python3.7/site-packages/mypy/main.py", line 92, in main
res = build.build(sources, options, None, flush_errors, fscache)
File "/usr/local/lib/python3.7/site-packages/mypy/build.py", line 155, in build
result = _build(sources, options, alt_lib_path, flush_errors, fscache)
File "/usr/local/lib/python3.7/site-packages/mypy/build.py", line 204, in _build
graph = dispatch(sources, manager)
File "/usr/local/lib/python3.7/site-packages/mypy/build.py", line 2172, in dispatch
process_graph(graph, manager)
File "/usr/local/lib/python3.7/site-packages/mypy/build.py", line 2469, in process_graph
process_stale_scc(graph, scc, manager)
File "/usr/local/lib/python3.7/site-packages/mypy/build.py", line 2592, in process_stale_scc
graph[id].type_check_first_pass()
File "/usr/local/lib/python3.7/site-packages/mypy/build.py", line 1730, in type_check_first_pass
self.type_checker().check_first_pass()
File "/usr/local/lib/python3.7/site-packages/mypy/checker.py", line 282, in check_first_pass
self.accept(d)
File "/usr/local/lib/python3.7/site-packages/mypy/checker.py", line 393, in accept
stmt.accept(self)
File "/usr/local/lib/python3.7/site-packages/mypy/nodes.py", line 845, in accept
return visitor.visit_class_def(self)
File "/usr/local/lib/python3.7/site-packages/mypy/checker.py", line 1536, in visit_class_def
self.accept(defn.defs)
File "/usr/local/lib/python3.7/site-packages/mypy/checker.py", line 393, in accept
stmt.accept(self)
File "/usr/local/lib/python3.7/site-packages/mypy/nodes.py", line 910, in accept
return visitor.visit_block(self)
File "/usr/local/lib/python3.7/site-packages/mypy/checker.py", line 1688, in visit_block
self.accept(s)
File "/usr/local/lib/python3.7/site-packages/mypy/checker.py", line 393, in accept
stmt.accept(self)
File "/usr/local/lib/python3.7/site-packages/mypy/nodes.py", line 608, in accept
return visitor.visit_func_def(self)
File "/usr/local/lib/python3.7/site-packages/mypy/checker.py", line 704, in visit_func_def
self._visit_func_def(defn)
File "/usr/local/lib/python3.7/site-packages/mypy/checker.py", line 708, in _visit_func_def
self.check_func_item(defn, name=defn.name())
File "/usr/local/lib/python3.7/site-packages/mypy/checker.py", line 770, in check_func_item
self.check_func_def(defn, typ, name)
File "/usr/local/lib/python3.7/site-packages/mypy/checker.py", line 787, in check_func_def
for item, typ in self.expand_typevars(defn, typ):
File "/usr/local/lib/python3.7/site-packages/mypy/checker.py", line 1280, in expand_typevars
result.append((expand_func(defn, mapping), expanded))
File "/usr/local/lib/python3.7/site-packages/mypy/checker.py", line 3931, in expand_func
ret = defn.accept(visitor)
File "/usr/local/lib/python3.7/site-packages/mypy/nodes.py", line 608, in accept
return visitor.visit_func_def(self)
File "/usr/local/lib/python3.7/site-packages/mypy/treetransform.py", line 106, in visit_func_def
[self.copy_argument(arg) for arg in node.arguments],
File "/usr/local/lib/python3.7/site-packages/mypy/treetransform.py", line 106, in <listcomp>
[self.copy_argument(arg) for arg in node.arguments],
File "/usr/local/lib/python3.7/site-packages/mypy/treetransform.py", line 80, in copy_argument
self.visit_var(argument.variable),
File "/usr/local/lib/python3.7/site-packages/mypy/treetransform.py", line 199, in visit_var
new = Var(node.name(), self.optional_type(node.type))
File "/usr/local/lib/python3.7/site-packages/mypy/treetransform.py", line 584, in optional_type
return self.type(type)
File "/usr/local/lib/python3.7/site-packages/mypy/checker.py", line 3942, in type
return expand_type(type, self.map)
File "/usr/local/lib/python3.7/site-packages/mypy/expandtype.py", line 16, in expand_type
return typ.accept(ExpandTypeVisitor(env))
File "/usr/local/lib/python3.7/site-packages/mypy/types.py", line 524, in accept
return visitor.visit_instance(self)
File "/usr/local/lib/python3.7/site-packages/mypy/expandtype.py", line 83, in visit_instance
args = self.expand_types(t.args)
File "/usr/local/lib/python3.7/site-packages/mypy/expandtype.py", line 132, in expand_types
a.append(t.accept(self))
File "/usr/local/lib/python3.7/site-packages/mypy/types.py", line 1532, in accept
return visitor.visit_forwardref_type(self)
File "/usr/local/lib/python3.7/site-packages/mypy/type_visitor.py", line 101, in visit_forwardref_type
raise RuntimeError('Internal error: unresolved forward reference')
RuntimeError: Internal error: unresolved forward reference
mypy_break.py:7: : note: use --pdb to drop into pdb
Activity
[-]Mapping[TypeVar, Union] under attrs breaks mypy[/-][+]Forward References under attrs classes extending Generic breaks mypy[/+]ilevkivskyi commentedon Nov 2, 2018
Any of these two should solve the problem:
modified, instead of passing the type astype=...Ideally, this should be supported, but at least mypy should not crash.
@euresti might help with this.
97littleleaf11 commentedon Oct 11, 2021
This issue cannot be reproduced in latest branch. It seems fine to close it.