Closed
Description
While writing an iterable file-like class class MyFileLike(object) I was having trouble getting the Iterable protocol to be implicitly recognized. So I decided to add an explicit Iterable parent:
from typing import Iterator, Iterable
class MyFileLike(object, Iterable[str]):
def readlines(self) -> Iterator[str]:
return iter(["one", "two", "three"])
__iter__ = readlines
m = MyFileLike()
it = iter(m)
for l in it: print(l)That snippet crashes mypy:
Traceback (most recent call last):
File "/home/machinalis/.virtualenvs/mypy-django/bin/mypy", line 6, in <module>
exec(compile(open(__file__).read(), __file__, 'exec'))
File "/home/machinalis/oss/mypy/scripts/mypy", line 6, in <module>
main(__file__)
File "/home/machinalis/oss/mypy/mypy/main.py", line 38, in main
res = type_check_only(sources, bin_dir, options)
File "/home/machinalis/oss/mypy/mypy/main.py", line 79, in type_check_only
options=options)
File "/home/machinalis/oss/mypy/mypy/build.py", line 180, in build
dispatch(sources, manager)
File "/home/machinalis/oss/mypy/mypy/build.py", line 1335, in dispatch
process_graph(graph, manager)
File "/home/machinalis/oss/mypy/mypy/build.py", line 1478, in process_graph
process_stale_scc(graph, scc)
File "/home/machinalis/oss/mypy/mypy/build.py", line 1551, in process_stale_scc
graph[id].semantic_analysis()
File "/home/machinalis/oss/mypy/mypy/build.py", line 1300, in semantic_analysis
self.manager.semantic_analyzer.visit_file(self.tree, self.xpath)
File "/home/machinalis/oss/mypy/mypy/semanal.py", line 244, in visit_file
self.accept(d)
File "/home/machinalis/oss/mypy/mypy/semanal.py", line 2462, in accept
node.accept(self)
File "/home/machinalis/oss/mypy/mypy/nodes.py", line 664, in accept
return visitor.visit_class_def(self)
File "/home/machinalis/oss/mypy/mypy/semanal.py", line 572, in visit_class_def
defn.defs.accept(self)
File "/home/machinalis/oss/mypy/mypy/nodes.py", line 727, in accept
return visitor.visit_block(self)
File "/home/machinalis/oss/mypy/mypy/semanal.py", line 1028, in visit_block
self.accept(s)
File "/home/machinalis/oss/mypy/mypy/semanal.py", line 2462, in accept
node.accept(self)
File "/home/machinalis/oss/mypy/mypy/nodes.py", line 765, in accept
return visitor.visit_assignment_stmt(self)
File "/home/machinalis/oss/mypy/mypy/semanal.py", line 1060, in visit_assignment_stmt
s.rvalue.accept(self)
File "/home/machinalis/oss/mypy/mypy/nodes.py", line 1116, in accept
return visitor.visit_name_expr(self)
File "/home/machinalis/oss/mypy/mypy/semanal.py", line 1906, in visit_name_expr
n = self.lookup(expr.name, expr)
File "/home/machinalis/oss/mypy/mypy/semanal.py", line 2250, in lookup
return self.type[name]
File "/home/machinalis/oss/mypy/mypy/nodes.py", line 1864, in __getitem__
raise KeyError(name)
KeyError: 'readlines'
*** INTERNAL ERROR ***
myiter.py:7: error: Internal error -- please report a bug at https://github.com/python/mypy/issues
NOTE: you can use "mypy --pdb ..." to drop into the debugger when this happens.
The crash goes away if I remove the object reference and only inherit from Iterable[str].