Crash on recursive namedtuple with Callable attribute

[JelleZijlstra]

To illustrate the bug with a more "realistic" example, here is the top of an Order class to demonstrate the Strategy pattern, where a concrete strategy is named a promotion, and it must be a callable that accepts an Order argument:

@dataclass
class Order:  # the Context
    customer: Customer
    cart: Sequence[LineItem]
    promotion: Optional[Callable[['Order'], float]] = None  # the Strategy

Mypy 0.910 accepts the code above, but crashes with the code below:

class Order(NamedTuple):
    customer: Customer
    cart: Sequence[LineItem]
    promotion: Optional[Callable[['Order'], float]] = None  # the Strategy

I put # type: ignore instead of # the Strategy on that line, but it did not help: Mypy still crashed.

The error:

$ mypy strategy_namedtuple.py 
Deferral trace:
    strategy_namedtuple:49
    strategy_namedtuple:49
    strategy_namedtuple:-1
    ... repeat those 3 lines many times ...
strategy_namedtuple.py: error: INTERNAL ERROR: maximum semantic analysis iteration count reached
strategy_namedtuple.py:71: error: Cannot resolve name "Order" (possible cyclic definition)
strategy_namedtuple.py:76: error: Cannot resolve name "Order" (possible cyclic definition)
strategy_namedtuple.py:85: error: Cannot resolve name "Order" (possible cyclic definition)
strategy_namedtuple.py: 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/luciano/flupy/.py310b3/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/__main__.py", line 11, in console_entry
    main(None, sys.stdout, sys.stderr)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/main.py", line 87, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/main.py", line 165, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/build.py", line 179, in build
    result = _build(
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/build.py", line 254, in _build
    graph = dispatch(sources, manager, stdout)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/build.py", line 2697, in dispatch
    process_graph(graph, manager)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/build.py", line 3021, in process_graph
    process_stale_scc(graph, scc, manager)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/build.py", line 3113, in process_stale_scc
    mypy.semanal_main.semantic_analysis_for_scc(graph, scc, manager.errors)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/semanal_main.py", line 84, in semantic_analysis_for_scc
    check_type_arguments(graph, scc, errors)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/semanal_main.py", line 358, in check_type_arguments
    with state.wrap_context():
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/contextlib.py", line 151, in __exit__
    self.gen.throw(type, value, traceback)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/build.py", line 1955, in wrap_context
    yield
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/semanal_main.py", line 360, in check_type_arguments
    state.tree.accept(analyzer)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/nodes.py", line 305, in accept
    return visitor.visit_mypy_file(self)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/semanal_typeargs.py", line 39, in visit_mypy_file
    super().visit_mypy_file(o)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/traverser.py", line 37, in visit_mypy_file
    d.accept(self)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/nodes.py", line 950, in accept
    return visitor.visit_class_def(self)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/semanal_typeargs.py", line 50, in visit_class_def
    super().visit_class_def(defn)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/mixedtraverser.py", line 28, in visit_class_def
    super().visit_class_def(o)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/traverser.py", line 73, in visit_class_def
    o.defs.accept(self)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/nodes.py", line 1015, in accept
    return visitor.visit_block(self)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/semanal_typeargs.py", line 54, in visit_block
    super().visit_block(o)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/traverser.py", line 41, in visit_block
    s.accept(self)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/nodes.py", line 687, in accept
    return visitor.visit_func_def(self)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/traverser.py", line 56, in visit_func_def
    self.visit_func(o)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/semanal_typeargs.py", line 46, in visit_func
    super().visit_func(defn)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/mixedtraverser.py", line 23, in visit_func
    self.visit_optional_type(o.type)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/mixedtraverser.py", line 91, in visit_optional_type
    t.accept(self)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/types.py", line 1156, in accept
    return visitor.visit_callable_type(self)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/typetraverser.py", line 52, in visit_callable_type
    t.fallback.accept(self)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/types.py", line 846, in accept
    return visitor.visit_instance(self)
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/semanal_typeargs.py", line 70, in visit_instance
    for (i, arg), tvar in zip(enumerate(t.args), info.defn.type_vars):
  File "/Users/luciano/flupy/.py310b3/lib/python3.10/site-packages/mypy/nodes.py", line 2705, in __getattribute__
    raise AssertionError(object.__getattribute__(self, 'msg'))
AssertionError: fallback can't be filled out until semanal
strategy_namedtuple.py: : note: use --pdb to drop into pdb

Originally posted by @ramalho in #9397 (comment)

[JelleZijlstra]

@ramalho I tried a full version of your example in the playground:

from typing import Optional, Callable, Sequence, NamedTuple

class LineItem:
    pass

class Customer:
    pass

class Order(NamedTuple):
    customer: Customer
    cart: Sequence[LineItem]
    promotion: Optional[Callable[['Order'], float]] = None  # the Strategy

But I get no crash, only the expected Cannot resolve name "Order" (possible cyclic definition). Can you provide a self-contained sample that reproduces the crash?

[JelleZijlstra]

There is another crash on recursive namedtuples (#8695), but the stack trace is different than the one @ramalho posted, so it might be a different underlying issue.

[ilevkivskyi]

This now works on master with --enable-recursive-aliases.