AssertionError: Must not defer during final iteration

[mrolle45]

I worked around this by commenting out the offending line 986. I'll leave it in place when not running mypy.
By the way:

• mypy disregarded my "# type: ignore" comment.
• The --show_traceback option didn't work on the command line, and I had to put it in mypy.ini.

D:\Solutions\trunk\Python\Sass>mypy --show_traceback=True solver\opnd_types.py > foo.txt
usage: mypy [-h] [-v] [-V] [more options; see below]
            [-m MODULE] [-p PACKAGE] [-c PROGRAM_TEXT] [files ...]
mypy: error: unrecognized arguments: --show_traceback=True

• mypy disregarded the exclude option in mypy.ini and reported errors on all three of these files.
  exclude = (pickler|profilerstats|solver/debugging)\.py

Crash Report

D:\Solutions\trunk\Python\Sass>mypy solver\opnd_types.py > foo.txt
mypy.ini: [mypy]: Unrecognized option: dummy = 3 [ I put this in to verify it was reading mypy.ini. ]
solver\opnd_types.py:986: 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: 0.931
solver\opnd_types.py:986: : note: use --pdb to drop into pdb

Traceback
This is the contents of the foo.txt written above...

outfile.py:29: error: Cannot assign to a method
outfile.py:32: error: Incompatible types in assignment (expression has type "str", variable has type "None")
outfile.py:37: error: Incompatible types in assignment (expression has type "TextIO", variable has type "None")
outfile.py:39: error: Incompatible types in assignment (expression has type "IO[Any]", variable has type "None")
profilerstats.py:309: error: Need type annotation for "newstats" (hint: "newstats: Dict[<type>, <type>] = ...")
profilerstats.py:429: error: Argument 1 to "print_title" of "Stats" has incompatible type "List[str]"; expected "Tuple[str, str, str, str, str]"
profilerstats.py:429: error: Argument 2 to "print_title" of "Stats" has incompatible type "Tuple[int, ...]"; expected "Tuple[int, int, int, int, int]"
profilerstats.py:448: error: Argument 3 to "print_call_heading" of "Stats" has incompatible type "List[str]"; expected "Tuple[str, str, str]"
profilerstats.py:448: error: Argument 4 to "print_call_heading" of "Stats" has incompatible type "Tuple[int, ...]"; expected "Tuple[int, int, int]"
profilerstats.py:451: error: Argument 4 to "print_call_line" of "Stats" has incompatible type "Tuple[int, ...]"; expected "Tuple[int, int, int]"
profilerstats.py:469: error: Argument 3 to "print_call_heading" of "Stats" has incompatible type "List[str]"; expected "Tuple[str, str, str]"
profilerstats.py:469: error: Argument 4 to "print_call_heading" of "Stats" has incompatible type "Tuple[int, ...]"; expected "Tuple[int, int, int]"
profilerstats.py:472: error: Argument 4 to "print_call_line" of "Stats" has incompatible type "Tuple[int, ...]"; expected "Tuple[int, int, int]"
profilerstats.py:509: error: Argument 1 to "call_items" of "Stats" has incompatible type "Tuple[Any, ...]"; expected "CallStats"
profilerstats.py:563: error: Invalid type comment or annotation
profilerstats.py:563: note: Suggestion: use Tuple[...] instead of Tuple(...)
profilerstats.py:576: error: Name "Mapping" is not defined
profilerstats.py:643: error: "CallStats" has no attribute "items"
profilerstats.py:645: error: "CallStats" has no attribute "items"
profilerstats.py:656: error: Incompatible return value type (got "Dict[Any, Any]", expected "CallStats")
profilerstats.py:842: error: Incompatible types in assignment (expression has type "None", variable has type "str")
solver\debugging.py:45: error: Name "InstrCtx" is not defined
solver\debugging.py:78: error: Need type annotation for "col_nums" (hint: "col_nums: List[<type>] = ...")
solver\debugging.py:89: error: Name "InstrCtx" is not defined
solver\debugging.py:94: error: Need type annotation for "debug_ignore_instr_nums" (hint: "debug_ignore_instr_nums: List[<type>] = ...")
solver\debugging.py:111: error: Missing positional argument "target" in call to "__call__" of "_Db"
solver\debugging.py:154: error: Name "debug_dump_codes_gen_thresh" already defined on line 153
solver\debugging.py:209: error: Cannot resolve name "_DebugBreakParams" (possible cyclic definition)
solver\debugging.py:241: error: Name "InstrTab" is not defined
solver\debugging.py:255: error: Name "OutFile" is not defined
solver\debugging.py:255: error: Name "InstrTab" is not defined
solver\debugging.py:270: error: Name "InstrTab" is not defined
solver\debugging.py:294: error: Name "CodeBits" is not defined
solver\debugging.py:302: error: Skipping analyzing "psutil": module is installed, but missing library stubs or py.typed marker
solver\debugging.py:302: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
solver\debugging.py:330: error: Skipping analyzing "psutil._common": module is installed, but missing library stubs or py.typed marker
solver\debugging.py:398: error: Need type annotation for "memo" (hint: "memo: Dict[<type>, <type>] = ...")
metaclasses.py:30: error: Incompatible return value type (got "Tuple[type, ...]", expected "Tuple[type]")
metaclasses.py:50: error: Need type annotation for "_memoized_metaclasses_map" (hint: "_memoized_metaclasses_map: Dict[<type>, <type>] = ...")
cache.py:43: error: Cannot assign to a method
cache.py:57: error: Name "WeakRef" is not defined
cache.py:57: error: Name "_CacheDir" is not defined
cache.py:100: error: Too many arguments for "_IterInKey"
cache.py:106: error: Too many arguments for "_IterInKey"
cache.py:112: error: All conditional function variants must have identical signatures
cache.py:125: error: Incompatible types in assignment (expression has type "Tuple[Tuple[Any, ...]]", variable has type "Tuple[Tuple[Any, ...], Tuple[Any, ...], Tuple[Any, ...]]")
cache.py:131: error: Name "__hash__" already defined on line 128
cache.py:134: error: Argument 1 of "__eq__" is incompatible with supertype "object"; supertype defines the argument type as "object"
cache.py:134: note: This violates the Liskov substitution principle
cache.py:134: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides
cache.py:134: note: It is recommended for "__eq__" to work with arbitrary objects, for example:
cache.py:134: note:     def __eq__(self, other: object) -> bool:
cache.py:134: note:         if not isinstance(other, _Key):
cache.py:134: note:             return NotImplemented
cache.py:134: note:         return <logic to compare two _Key instances>
cache.py:145: error: "_Key" has no attribute "args"
cache.py:147: error: "_Key" has no attribute "kwds"; maybe "nokwds" or "kwords"?
cache.py:158: error: Invalid base class "Callable"
cache.py:195: error: Signature of "update" incompatible with supertype "dict"
cache.py:195: note:      Superclass:
cache.py:195: note:          @overload
cache.py:195: note:          def update(self, Mapping[Any, Any], **kwargs: Any) -> None
cache.py:195: note:          @overload
cache.py:195: note:          def update(self, Iterable[Tuple[Any, Any]], **kwargs: Any) -> None
cache.py:195: note:          @overload
cache.py:195: note:          def update(self, **kwargs: Any) -> None
cache.py:195: note:      Subclass:
cache.py:195: note:          def update(self, key: Any, result: Any, bypass: bool = ...) -> Any
cache.py:195: error: Signature of "update" incompatible with supertype "MutableMapping"
cache.py:195: note:          @overload
cache.py:195: note:          def update(self, Mapping[Any, Any], **kwargs: Any) -> None
cache.py:195: note:          @overload
cache.py:195: note:          def update(self, Iterable[Tuple[Any, Any]], **kwargs: Any) -> None
cache.py:195: note:          @overload
cache.py:195: note:          def update(self, **kwargs: Any) -> None
cache.py:195: note:          def update(self, key: Any, result: Any, bypass: bool = ...) -> Any
cache.py:222: error: Signature of "get" incompatible with supertype "Mapping"
cache.py:222: note:      Superclass:
cache.py:222: note:          @overload
cache.py:222: note:          def get(self, key: Any) -> Optional[Any]
cache.py:222: note:          @overload
cache.py:222: note:          def [_T] get(self, Any, Union[Any, _T]) -> Union[Any, _T]
cache.py:222: note:      Subclass:
cache.py:222: note:          @classmethod
cache.py:222: note:          def get(cls, target: Any, name: Any, enabled: bool) -> Any
cache.py:245: error: Name "self" is not defined
cache.py:330: error: Signature of "__call__" incompatible with supertype "_CacheMgr"
cache.py:330: note:      Superclass:
cache.py:330: note:          def __call__(self, args: Tuple[Any, ...], kwds: Dict[Any, Any] = ..., *, bypass: bool = ..., key_class: type = ...) -> Any
cache.py:330: note:      Subclass:
cache.py:330: note:          def __call__(self, bypass: bool = ..., _key: Any = ...) -> Any
cache.py:423: error: All conditional function variants must have identical signatures
cache.py:426: error: All conditional function variants must have identical signatures
cache.py:428: error: Too many arguments for "get_cache"
cache.py:428: error: Missing positional argument "args" in call to "__call__" of "_CacheMgr"
cache.py:444: error: All conditional function variants must have identical signatures
cache.py:447: error: All conditional function variants must have identical signatures
cache.py:449: error: Too many arguments for "get_cache"
cache.py:466: error: All conditional function variants must have identical signatures
cache.py:469: error: All conditional function variants must have identical signatures
cache.py:471: error: Too many arguments for "get_cache"
cache.py:552: error: Incompatible return value type (got "PropWrapper", expected "Callable[[Any], Any]")
cache.py:629: error: Variable "mcls" is not valid as a type
cache.py:629: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases
cache.py:629: error: Invalid base class "mcls"
cache.py:652: error: Name "__class__" is not defined
cache.py:671: error: Cannot assign to a method
cache.py:683: error: Cannot assign to a method
cache.py:703: error: All conditional function variants must have identical signatures
cache.py:734: error: Cannot assign to a method
cache.py:734: error: Incompatible types in assignment (expression has type "object", variable has type "Callable[[type, VarArg(Any), KwArg(Any)], Any]")
cache.py:738: error: Cannot assign to a method
cache.py:843: error: Signature of "update" incompatible with supertype "_Missing"
cache.py:843: note:      Superclass:
cache.py:843: note:          def update(self, obj: Any, **kwds: Any) -> Any
cache.py:843: note:      Subclass:
cache.py:843: note:          def update(self, result: Any, **kwds: Any) -> Any
cache.py:854: error: Signature of "update" incompatible with supertype "_Missing"
cache.py:854: note:      Superclass:
cache.py:854: note:          def update(self, obj: Any, **kwds: Any) -> Any
cache.py:854: note:      Subclass:
cache.py:854: note:          def update(self, result: Any) -> Any
cache.py:912: error: Argument 2 to "CombineMeta" has incompatible type "Tuple[type, ...]"; expected "Tuple[type]"
cache.py:933: error: Incompatible return value type (got "type", expected "CacheBase")
cache.py:938: error: <nothing> has no attribute "__mro_entries__"
cache.py:939: error: Incompatible types in assignment (expression has type "None", variable has type "Type[type]")
cache.py:942: error: Invalid statement in NamedTuple definition; expected "field_name: field_type [= default]"
cache.py:948: error: Invalid statement in NamedTuple definition; expected "field_name: field_type [= default]"
cache.py:1010: error: "CachedTupleMeta" has no attribute "_nt_cls"
solver\common.py:12: error: Incompatible import of "Protocol" (imported name has type "typing_extensions._SpecialForm", local name has type "typing._SpecialForm")
solver\common.py:12: error: Incompatible import of "get_type_hints" (imported name has type "Callable[[Callable[..., Any], Optional[Dict[str, Any]], Optional[Dict[str, Any]], bool], Dict[str, Any]]", local name has type "Callable[[Union[object, Callable[..., Any], FunctionType, BuiltinFunctionType, MethodType, Module, WrapperDescriptorType, MethodWrapperType, MethodDescriptorType], Optional[Dict[str, Any]], Optional[Dict[str, Any]]], Dict[str, Any]]")
solver\common.py:12: note: (Skipping most remaining errors due to unresolved imports or missing stubs; fix these first)
solver\common.py:225: error: Dynamic metaclass not supported for "Bits64Cached"
solver\common.py:230: error: Type cannot be declared in assignment to non-self attribute
solver\common.py:250: error: Name "__class__" is not defined
solver\common.py:308: error: Name "num_bits" already defined on line 265
solver\common.py:424: error: Variable "solver.common.SubCode" is not valid as a type
solver\common.py:424: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases
solver\common.py:424: error: Invalid base class "SubCode"
solver\common.py:465: error: Variable "solver.common.SubCode" is not valid as a type
solver\common.py:465: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases
solver\common.py:467: error: Name "InstrTab" is not defined
solver\common.py:467: error: Variable "solver.common.BinCode" is not valid as a type
solver\common.py:467: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases
solver\common.py:485: error: Name "iterable" is not defined
solver\common.py:485: note: Did you forget to import it from "typing"? (Suggestion: "from typing import Iterable")
solver\common.py:538: error: Name "method" is not defined
Deferral trace:
    About 18,000 lines...
pickler.py:233: error: Cannot find implementation or library stub for module named "org.python.core"
pickler.py:1842: error: Cannot find implementation or library stub for module named "_pickle"
Traceback (most recent call last):
  File "D:\Python37\lib\runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "D:\Python37\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "mypy\semanal.py", line 5142, in accept
  File "mypy\nodes.py", line 1246, in accept
  File "mypy\semanal.py", line 3604, in visit_assert_stmt
  File "mypy\nodes.py", line 1713, in accept
  File "mypy\semanal.py", line 3943, in visit_call_expr
  File "mypy\nodes.py", line 1633, in accept
  File "mypy\semanal.py", line 3996, in visit_member_expr
  File "mypy\semanal.py", line 4448, in get_module_symbol
  File "mypy\semanal.py", line 4843, in record_incomplete_ref
  File "mypy\semanal.py", line 4826, in defer
AssertionError: Must not defer during final iteration

To Reproduce

Here is excerpt from opnd_types.py:

class FieldCategory(IntEnum):
	""" Names used to prefix the capture group name for a field.
	The enum's name is used to get a value of that category for a Body, or the substring of its name.
	The enum's value is used to sort display of multiple FieldGroups in the same Col.
	"""
	bnk = auto()
	num = auto()
	off = auto()

	def __init__(self, num):
		self.cap_name = f'cap_{self.name}'
		self.cap_str = attrgetter(f'type.cap_{self.name}')
		self.val_method: Callable[[OpndBody], FieldCatVal] = methodcaller(f'{self.name}_val')

	def get_val(self, body: Body):
		""" The computed value of the body for this category.
		It is a property of the body whose name depends on the body's type.
		"""
		# The following line crashes mypy!
		assert isinstance(body, bodies.Body)	# type:ignore         [ line 986 with INTERNAL ERROR ]
		return self.val_method(body)
	
from solver import  bodies
	

Excerpt from solver/bodies.py:

from .opnd_types import *
class Body(BodyBase, InstrValCommon):
    ...

(Write what you did to reproduce the crash. Full source code is
appreciated. We also very much appreciate it if you try to narrow the
source down to a small stand-alone example.)

Your Environment

• Mypy version used: 0.931
• Mypy configuration options from mypy.ini (and other config files):```

# Configuration for running mypy on this project.

[mypy]

#exclude = (?x)(
#    ^pickler\.py$
#    | ^profilerstats\.py$
#    | cache\.py$
#    | common\.py$
#    | ^(cubin|grammar)\.py$
#  )
#
exclude = (pickler|profilerstats|solver/debugging)\.py
dummy = 3
show_traceback = True

• Python version used: 3.7
• Operating system and version: Win 10

[AlexWaygood]

Same assertion is hit in #12113, #10140, #10672, #11728 and #12112

[RobertCraigie]

I've also encountered this error. I'm not sure if it's the same cause but here's the changes that triggered the error: https://github.com/RobertCraigie/prisma-client-py/pull/366/files.

For context, that module contains a lot of nested classes and is only really used in a few places, I haven't managed to narrow down the exact line that causes the error yet.

[hauntsaninja]

Thanks for the reports! We've fixed several issues that could lead to this; can anyone still repro an issue on master?