internal error when inferring type of callable resulting from untyped ternary expression #9234
Description
Consider the following example:
import random
from typing import Union, Callable
class Wrapper:
def __init__(self, x):
self.x = x
def main() -> Union[Wrapper, int]:
wrap = Wrapper if random.random() < 0.5 else lambda x: x
return wrap(2)
Running mypy (from the master branch in the repo) on it crashes with the following stack trace:
mypytest.py:18: error: INTERNAL ERROR -- Please try using mypy master on Github:
https://mypy.rtfd.io/en/latest/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 0.790+dev.cc46692020ef6b672b761512095fbba281fdefc7
Traceback (most recent call last):
File "/home/edo/miniconda3/envs/abm2/bin/mypy", line 8, in <module>
sys.exit(console_entry())
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/__main__.py", line 8, in console_entry
main(None, sys.stdout, sys.stderr)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/main.py", line 89, in main
res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/build.py", line 180, in build
result = _build(
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/build.py", line 252, in _build
graph = dispatch(sources, manager, stdout)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/build.py", line 2626, in dispatch
process_graph(graph, manager)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/build.py", line 2949, in process_graph
process_stale_scc(graph, scc, manager)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/build.py", line 3047, in process_stale_scc
graph[id].type_check_first_pass()
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/build.py", line 2107, in type_check_first_pass
self.type_checker().check_first_pass()
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checker.py", line 294, in check_first_pass
self.accept(d)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checker.py", line 401, in accept
stmt.accept(self)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/nodes.py", line 677, in accept
return visitor.visit_func_def(self)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checker.py", line 726, in visit_func_def
self._visit_func_def(defn)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checker.py", line 730, in _visit_func_def
self.check_func_item(defn, name=defn.name)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checker.py", line 792, in check_func_item
self.check_func_def(defn, typ, name)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checker.py", line 975, in check_func_def
self.accept(item.body)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checker.py", line 401, in accept
stmt.accept(self)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/nodes.py", line 1005, in accept
return visitor.visit_block(self)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checker.py", line 1973, in visit_block
self.accept(s)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checker.py", line 401, in accept
stmt.accept(self)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/nodes.py", line 1141, in accept
return visitor.visit_return_stmt(self)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checker.py", line 3156, in visit_return_stmt
self.check_return_stmt(s)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checker.py", line 3188, in check_return_stmt
typ = get_proper_type(self.expr_checker.accept(
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checkexpr.py", line 3768, in accept
typ = node.accept(self)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/nodes.py", line 1545, in accept
return visitor.visit_call_expr(self)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checkexpr.py", line 263, in visit_call_expr
return self.visit_call_expr_inner(e, allow_none_return=allow_none_return)
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checkexpr.py", line 340, in visit_call_expr_inner
ret_type = self.check_call_expr_with_callee_type(callee_type, e, fullname,
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checkexpr.py", line 817, in check_call_expr_with_callee_type
return self.check_call(callee_type, e.args, e.arg_kinds, e,
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checkexpr.py", line 876, in check_call
return self.check_callable_call(callee, args, arg_kinds, context, arg_names,
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/checkexpr.py", line 941, in check_callable_call
if (callee.is_type_obj() and callee.type_object().is_abstract
File "/home/edo/miniconda3/envs/abm2/lib/python3.8/site-packages/mypy/types.py", line 1094, in type_object
assert isinstance(ret, Instance)
AssertionError:
mypytest.py:18: : note: use --pdb to drop into pdb
Where ret is Any and callee in the frame above is def (x: Any) -> Any.
The error can be prevented either by assigning the lambda to a variable
identity = lambda x: x
wrap = Wrapper if random.random() < 0.5 else identity
where in this case no issues are reported, or the wrapper:
class Wrapper:
def __init__(self, x: int) -> None:
self.x = x
def main() -> Union[Wrapper, int]:
wrap = Wrapper if random.random() < 0.5 else lambda x: x
but in this case two errors are reported (line 12 is wrap = and line 14 is return
mypytest.py:12: error: Incompatible return value type (got "int", expected "Wrapper")
mypytest.py:14: error: Incompatible return value type (got "object", expected "Union[Wrapper, int]")
these erros do not occur when both fixes are applied.
expected behavior: no errors reported in all three cases, or at least no crash.