Use of built-in open() causes crash if file named io.py

[lillekemiker]

Crash Report

Running mypy on a file named io.py that uses the built-in open() function causes and internal error to occur.

Traceback

utils/io.py:2: error: INTERNAL ERROR -- Please try using mypy master on Github:
https://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 0.910
Traceback (most recent call last):
  File "/Users/martinkristiansen/.pyenv/versions/tmp-delete/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/__main__.py", line 11, in console_entry
    main(None, sys.stdout, sys.stderr)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/main.py", line 87, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/main.py", line 165, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/build.py", line 179, in build
    result = _build(
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/build.py", line 254, in _build
    graph = dispatch(sources, manager, stdout)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/build.py", line 2697, in dispatch
    process_graph(graph, manager)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/build.py", line 3021, in process_graph
    process_stale_scc(graph, scc, manager)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/build.py", line 3119, in process_stale_scc
    graph[id].type_check_first_pass()
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/build.py", line 2165, in type_check_first_pass
    self.type_checker().check_first_pass()
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checker.py", line 294, in check_first_pass
    self.accept(d)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checker.py", line 401, in accept
    stmt.accept(self)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/nodes.py", line 687, in accept
    return visitor.visit_func_def(self)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checker.py", line 726, in visit_func_def
    self._visit_func_def(defn)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checker.py", line 730, in _visit_func_def
    self.check_func_item(defn, name=defn.name)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checker.py", line 792, in check_func_item
    self.check_func_def(defn, typ, name)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checker.py", line 975, in check_func_def
    self.accept(item.body)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checker.py", line 401, in accept
    stmt.accept(self)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/nodes.py", line 1015, in accept
    return visitor.visit_block(self)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checker.py", line 1975, in visit_block
    self.accept(s)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checker.py", line 401, in accept
    stmt.accept(self)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/nodes.py", line 1268, in accept
    return visitor.visit_with_stmt(self)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checker.py", line 3638, in visit_with_stmt
    exit_ret_type = self.check_with_item(expr, target, s.unanalyzed_type is None)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checker.py", line 3693, in check_with_item
    ctx = echk.accept(expr)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checkexpr.py", line 3911, in accept
    typ = node.accept(self)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/nodes.py", line 1558, in accept
    return visitor.visit_call_expr(self)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checkexpr.py", line 271, in visit_call_expr
    return self.visit_call_expr_inner(e, allow_none_return=allow_none_return)
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checkexpr.py", line 353, in visit_call_expr_inner
    ret_type = self.check_call_expr_with_callee_type(callee_type, e, fullname,
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checkexpr.py", line 858, in check_call_expr_with_callee_type
    return self.check_call(callee_type, e.args, e.arg_kinds, e,
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checkexpr.py", line 921, in check_call
    return self.check_overload_call(callee, args, arg_kinds, arg_names, callable_name,
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checkexpr.py", line 1578, in check_overload_call
    inferred_result = self.infer_overload_return_type(plausible_targets, args, arg_types,
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checkexpr.py", line 1721, in infer_overload_return_type
    ret_type, infer_type = self.check_call(
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checkexpr.py", line 917, in check_call
    return self.check_callable_call(callee, args, arg_kinds, context, arg_names,
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checkexpr.py", line 1029, in check_callable_call
    new_ret_type = self.apply_function_plugin(
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/checkexpr.py", line 729, in apply_function_plugin
    return callback(
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/plugins/default.py", line 126, in open_callback
    return _analyze_open_signature(
  File "/Users/martinkristiansen/.pyenv/versions/3.8.8/envs/tmp-delete/lib/python3.8/site-packages/mypy/plugins/default.py", line 168, in _analyze_open_signature
    assert isinstance(default_return_type, Instance)  # type: ignore
AssertionError: 
utils/io.py:2: : note: use --pdb to drop into pdb

To Reproduce

Minimal working (crashing) example:

def export_file(src: str) -> str:
    with open(src) as f:
        data = f.read()
    return data

Save above to a file named io.py and run mypy on the file.
If the file is named something else, the error goes away.

Your Environment

• Mypy version used: 0.910 and current master (2105532)
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files): None
• Python version used: 3.8.8
• Operating system and version: macOS 11.4

Minimal pyenv virtual environment used:

mypy==0.910
mypy-extensions==0.4.3
toml==0.10.2
typing-extensions==3.10.0.0

[JelleZijlstra]

Shadowing the standard library is often going to cause issues. Mypy shouldn't crash, though.

[lillekemiker]

Just to be clear, the original issue was observed in a repo where the io.py file was placed in a sub-namespace so there was no issue with namespace collisions.

[Michael0x2a]

This no longer repros -- looks like the crash was fixed by #9275, according to git-bisect.