Draft: Solve intermediate variable bug #19399

randolf-scholz · 2025-07-08T11:59:48Z

Looking for feedback, as this was mostly a trial-and-error process.

Removed self.infer_function_type_arguments_using_context. Instead, we now use a function infer_constraints_from_context that only yields the constraints.
Modified infer_function_type_arguments to now include the context.
We compute 2 sets of constraints: the "outer constraints", determined by the context, and the "inner constraints" determined by the callable type. From this, we compute 2 solutions:
- the "outer solution", which only uses the outer constraints.
- the "joint solution", which uses both the outer and inner constraints.
We prefer the "joint solution", unless:
- it failed to solve some variables
- the return type of the outer solution is a (strict) subtype (i.e. more precise) of the return type of the joint solution
- ~~the return type of the outer solution is a union, and any member of that union is a subtype of the joint return type.¹~~
if the outer solution was selected, we essentially fall back to the original code from the master branch, and first apply the outer solution, and then recompute the inner constraints and apply the inner solution.

New Tests

testBinaryOperatorContext mypy-playground
testContextFreeConcatInvariantType mypy-playground
testInContextConcatInvariantType mypy-playground
testLiteralMappingContext: mypy-playground new test based on a failure in pandas-stubs.

Modified Tests

testRecursiveAliasWithRecursiveInstance: improved inference²
testCallerTupleVarArgsAndGenericCalleeVarArg now reveals int | None rather than Literal[1]? | None³
testInferenceAgainstGenericCallableGenericProtocol now reveals F[T | None] rather than def [T] (T|None) -> T|None⁴
testInferenceAgainstGenericParamSpecPopOn now reveals def (U) -> U rather than def [T] (T) -> T⁵

This was needed to fix testLiteralAndGenericWithUnion, because the outer solution was int | Literal["foo"] whereas the joint solution was Literal["foo"]? which got converted into str later. ↩
previously, a=b followed by a=[[b]] made a be inferred as __main__.B followed by builtins.list[Union[__main__.A, typing.Sequence[Union[__main__.A, ...]]]]. Now, it gets more precisely inferred as builtins.list[builtins.list[__main__.B]]. And afterwards, join(a,b) get more precisely inferred as typing.Sequence[typing.Sequence[__main__.B]] rather than typing.Sequence[Union[__main__.A, typing.Sequence[Union[__main__.A, ...]]]] previously. See: https://mypy-play.net/?mypy=latest&python=3.12&gist=619a7fa6c3ec9d75bd1492bf8e68432c. The new result is also more in line with the inference by pyright ↩
same as pyright ↩
same as pyright ↩
same as pyright ↩

mypy/checkexpr.py

randolf-scholz · 2025-07-08T12:04:09Z

mypy/checkexpr.py

+                            lambda i: self.accept(args[i]),
+                        )
+
+                    # ??? QUESTION: Do we need to recompute arg_types and pass1_args here???


It seems to work both with/without recomputing arg_types here, but I am not sure.

randolf-scholz · 2025-07-09T11:24:13Z

mypy/checkexpr.py

+                # HACK: convert "Literal?" constraints to their non-literal versions.
+                inner_constraints: list[Constraint] = []
+                for constraint in _inner_constraints:
+                    target = get_proper_type(constraint.target)
+                    inner_constraints.append(
+                        Constraint(
+                            constraint.original_type_var,
+                            constraint.op,
+                            (
+                                target.copy_modified(last_known_value=None)
+                                if isinstance(target, Instance)
+                                else target
+                            ),
+                        )
+                    )


This hack is needed for testLiteralAndGenericWithUnion and testLiteralMappingContext.

The only purpose is to convert constraints like T ≷ Literal['foo"]? to T ≷ str, which, in these test cases, causes the joint solution to fail due to incompatible constraints like T <: Literal["foo"] and T :> str, hence the longer route of using the outer solution first is used.

randolf-scholz · 2025-07-09T17:32:27Z

This still isn't quite correct; there are persisting issues with considering the outer context,

for example

from typing import TypedDict

class A: ...
class B(A): ...

class OverridesItem[T](TypedDict):
    tp: type[T]

d: dict[str, OverridesItem[A]] = {"foo": OverridesItem(tp=B)}

gives

error: Dict entry 0 has incompatible type "str": "OverridesItem[B]"; expected "str": "OverridesItem[A]"  [dict-item]

with the current version of the PR.

It seems that these issues stem from "solving" variables too eagerly.

In the example above, def [T] (*, tp: type[T`501]) -> TypedDict('tmp_b.OverridesItem', {'tp': type[T`501]}) yields the "solution" T=B, although the constraints only require T :> B, which would allow T=A later on. So possibly the solution should be delayed until the interval (lower, upper) collapses to a single point.

…iantType

github-actions · 2025-07-24T15:07:20Z

Diff from mypy_primer, showing the effect of this PR on open source code:

colour (https://github.com/colour-science/colour)
+ colour/utilities/array.py:2428: error: Argument 1 to "__call__" of "_FloatOp" has incompatible type "floating[_16Bit]"; expected "integer[_32Bit] | floating[_32Bit]"  [arg-type]
+ colour/utilities/array.py:2428: error: Argument 1 to "__call__" of "_FloatOp" has incompatible type "floating[_32Bit]"; expected "integer[_16Bit] | floating[_16Bit]"  [arg-type]
+ colour/utilities/array.py:2428: note: Both left and right operands are unions

static-frame (https://github.com/static-frame/static-frame)
+ static_frame/core/store.py:181: error: Argument 1 to "extend" of "list" has incompatible type "Sequence[TLabel]"; expected "Iterable[str]"  [arg-type]
+ static_frame/core/store.py:181: error: Argument 1 to "extend" of "list" has incompatible type "Sequence[TLabel]"; expected "Iterable[tuple[str, ...]]"  [arg-type]
+ static_frame/core/store.py:183: error: Argument 1 to "extend" of "list" has incompatible type "range"; expected "Iterable[str]"  [arg-type]
+ static_frame/core/store.py:183: note: Following member(s) of "range" have conflicts:
+ static_frame/core/store.py:183: note:     Expected:
+ static_frame/core/store.py:183: note:         def __iter__(self) -> Iterator[str]
+ static_frame/core/store.py:183: note:     Got:
+ static_frame/core/store.py:183: note:         def __iter__(self) -> Iterator[int]
+ static_frame/core/store.py:183: error: Argument 1 to "extend" of "list" has incompatible type "range"; expected "Iterable[tuple[str, ...]]"  [arg-type]
+ static_frame/core/store.py:183: note: Following member(s) of "range" have conflicts:
+ static_frame/core/store.py:183: note:     Expected:
+ static_frame/core/store.py:183: note:         def __iter__(self) -> Iterator[tuple[str, ...]]
+ static_frame/core/store.py:183: note:     Got:
+ static_frame/core/store.py:183: note:         def __iter__(self) -> Iterator[int]

pandas (https://github.com/pandas-dev/pandas)
+ pandas/core/arrays/datetimelike.py:2405: error: Unused "type: ignore" comment  [unused-ignore]
+ pandas/io/formats/csvs.py:141: error: List item 0 has incompatible type "Hashable"; expected "str"  [list-item]
+ pandas/tests/series/accessors/test_dt_accessor.py:441: error: Unused "type: ignore" comment  [unused-ignore]
+ pandas/tests/scalar/timestamp/test_timestamp.py:124: error: Unused "type: ignore" comment  [unused-ignore]
+ pandas/tests/indexes/datetimes/test_scalar_compat.py:141: error: Unused "type: ignore" comment  [unused-ignore]
+ pandas/tests/dtypes/test_missing.py:806: error: Unused "type: ignore" comment  [unused-ignore]
+ pandas/tests/dtypes/test_missing.py:828: error: Unused "type: ignore" comment  [unused-ignore]
+ pandas/conftest.py:1664: error: Unused "type: ignore" comment  [unused-ignore]

artigraph (https://github.com/artigraph/artigraph)
+ src/arti/graphs/__init__.py:181: error: Unused "type: ignore" comment  [unused-ignore]

steam.py (https://github.com/Gobot1234/steam.py)
+ steam/abc.py:552: error: Value of type variable "AppT" of "FavouriteBadge" cannot be "PartialApp[str | None] | tuple[str, int]"  [type-var]
- steam/state.py:1453: error: Argument 2 to "pop" of "dict" has incompatible type "None"; expected "ClanInvite | GroupInvite"  [arg-type]
+ steam/state.py:1453: error: Incompatible types in assignment (expression has type "ClanInvite | GroupInvite | None", variable has type "ClanInvite | GroupInvite")  [assignment]

zulip (https://github.com/zulip/zulip)
+ zproject/config.py:38: error: Argument "fallback" to "get" of "RawConfigParser" has incompatible type "str | None"; expected "None"  [arg-type]

jax (https://github.com/google/jax)
+ jax/_src/numpy/lax_numpy.py:2225: error: Unsupported operand types for - ("Sequence[int | Any]" and "int")  [operator]
+ jax/_src/numpy/lax_numpy.py:2225: note: Left operand is of type "Sequence[int | Any] | int | Any"

scikit-learn (https://github.com/scikit-learn/scikit-learn)
- sklearn/linear_model/tests/test_ridge.py:744: error: Unsupported operand types for + ("list[None]" and "list[ABCMeta]")  [operator]

prefect (https://github.com/PrefectHQ/prefect)
- src/prefect/utilities/callables.py:579: error: Incompatible types in assignment (expression has type "list[None]", variable has type "list[Optional[expr]]")  [assignment]
- src/prefect/utilities/callables.py:579: note: "list" is invariant -- see https://mypy.readthedocs.io/en/stable/common_issues.html#variance
- src/prefect/utilities/callables.py:579: note: Consider using "Sequence" instead, which is covariant
- src/prefect/utilities/callables.py:581: error: Unsupported operand types for + ("list[None]" and "list[Optional[expr]]")  [operator]
+ src/prefect/client/orchestration/__init__.py:1088: error: Function does not return a value (it only ever returns None)  [func-returns-value]

operator (https://github.com/canonical/operator)
- ops/model.py:2937: error: Argument 2 to "_list_recursive" of "Container" has incompatible type "str | Path"; expected "Path"  [arg-type]
- ops/model.py:3020: error: Argument 2 to "_list_recursive" of "Container" has incompatible type "str | Path"; expected "Path"  [arg-type]
- ops/_private/harness.py:4003: error: Argument 3 to "_notice_matches" of "_TestingPebbleClient" has incompatible type "set[NoticeType | str] | None"; expected "set[str] | None"  [arg-type]

Expression (https://github.com/cognitedata/Expression)
+ expression/collections/block.py:271: error: Incompatible return value type (got "int", expected "_TSourceSum | Literal[0]")  [return-value]
+ expression/collections/block.py:271: error: Argument 1 to "sum" has incompatible type "tuple[_TSourceSum | Literal[0], ...]"; expected "Iterable[bool]"  [arg-type]
+ expression/collections/block.py:934: error: Incompatible return value type (got "int", expected "_TSourceSum | Literal[0]")  [return-value]
+ expression/collections/block.py:934: error: Argument 1 to "sum" has incompatible type "Block[_TSourceSum | Literal[0]]"; expected "Iterable[bool]"  [arg-type]

discord.py (https://github.com/Rapptz/discord.py)
- discord/ext/commands/bot.py:1316: error: Argument 1 to "find" has incompatible type "Callable[[str], bool]"; expected "Callable[[list[str] | str], Any]"  [arg-type]

pydantic (https://github.com/pydantic/pydantic)
- pydantic/aliases.py:29: error: Incompatible types in assignment (expression has type "list[str]", variable has type "list[int | str]")  [assignment]
- pydantic/aliases.py:29: note: "list" is invariant -- see https://mypy.readthedocs.io/en/stable/common_issues.html#variance
- pydantic/aliases.py:29: note: Consider using "Sequence" instead, which is covariant
- pydantic/aliases.py:29: error: Argument 1 to "list" has incompatible type "tuple[str | int, ...]"; expected "Iterable[str]"  [arg-type]

hydra-zen (https://github.com/mit-ll-responsible-ai/hydra-zen)
- src/hydra_zen/wrapper/_implementations.py:1756: error: Unsupported operand types for + ("list[None]" and "list[str]")  [operator]

xarray (https://github.com/pydata/xarray)
+ xarray/core/dataset.py: note: In member "drop_dims" of class "Dataset":
+ xarray/core/dataset.py:6107: error: Argument 1 to "set" has incompatible type "Frozen[Hashable, int]"; expected "Iterable[str | None]"  [arg-type]
+ xarray/core/dataset.py:6107: note: Left operand is of type "set[str] | set[Hashable]"
+ xarray/core/dataset.py: note: At top level:
+ xarray/core/dataarray.py: note: In function "_infer_coords_and_dims":
+ xarray/core/dataarray.py:163: error: No overload variant of "__setitem__" of "list" matches argument types "int", "Hashable"  [call-overload]
+ xarray/core/dataarray.py:163: note: Possible overload variants:
+ xarray/core/dataarray.py:163: note:     def __setitem__(self, SupportsIndex, str, /) -> None
+ xarray/core/dataarray.py:163: note:     def __setitem__(self, slice[Any, Any, Any], Iterable[str], /) -> None
+ xarray/core/dataarray.py:186: error: Incompatible types in assignment (expression has type "Hashable", variable has type "str")  [assignment]
+ xarray/core/dataarray.py: note: At top level:
+ xarray/tests/test_dataarray.py:423: error: Unused "type: ignore" comment  [unused-ignore]

spark (https://github.com/apache/spark)
+ python/pyspark/ml/util.py:1166: error: Unused "type: ignore" comment  [unused-ignore]
+ python/pyspark/ml/classification.py:3976: error: Unused "type: ignore" comment  [unused-ignore]

sympy (https://github.com/sympy/sympy)
+ sympy/core/add.py:384: error: Unused "type: ignore" comment  [unused-ignore]

antidote (https://github.com/Finistere/antidote)
+ tests/lib/interface/test_custom.py:434: error: Unused "type: ignore" comment  [unused-ignore]
+ tests/lib/interface/test_custom.py:437: error: Unused "type: ignore" comment  [unused-ignore]
+ tests/lib/interface/test_custom.py:440: error: Unused "type: ignore" comment  [unused-ignore]
+ tests/lib/interface/test_custom.py:443: error: Unused "type: ignore" comment  [unused-ignore]
+ tests/lib/interface/test_custom.py:446: error: Unused "type: ignore" comment  [unused-ignore]
+ tests/lib/interface/test_custom.py:449: error: Unused "type: ignore" comment  [unused-ignore]

core (https://github.com/home-assistant/core)
+ homeassistant/helpers/service.py:986: error: Argument 1 to "HassJob" has incompatible type "Callable[[ServiceCall], Coroutine[Any, Any, ServiceResponse | EntityServiceResponse] | ServiceResponse | EntityServiceResponse | None]"; expected "Callable[[VarArg([ServiceCall] | [ServiceCall]), KwArg([ServiceCall] | [ServiceCall])], Coroutine[Any, Any, ServiceResponse | EntityServiceResponse] | JsonObjectType | EntityServiceResponse | JsonObjectType | EntityServiceResponse | None]"  [arg-type]
+ homeassistant/components/motioneye/media_source.py:96: error: Unused "type: ignore" comment  [unused-ignore]

scipy-stubs (https://github.com/scipy/scipy-stubs)
+ tests/sparse/test_construct.pyi:245: error: Expression is of type "coo_array[_ScalarT, tuple[int, int]]", not "coo_array[float64, tuple[int, int]]"  [assert-type]
+ tests/sparse/test_construct.pyi:246: error: Expression is of type "csc_array[_ScalarT]", not "csc_array[float64]"  [assert-type]
+ tests/sparse/test_construct.pyi:247: error: Expression is of type "csr_array[_ScalarT, tuple[int, int]]", not "csr_array[float64, tuple[int, int]]"  [assert-type]
+ tests/sparse/test_construct.pyi:248: error: Expression is of type "coo_array[_ScalarT, tuple[int, int]]", not "coo_array[complex128, tuple[int, int]]"  [assert-type]
+ tests/sparse/test_construct.pyi:249: error: Expression is of type "coo_array[_ScalarT, tuple[int, int]]", not "coo_array[complex128, tuple[int, int]]"  [assert-type]
+ tests/sparse/test_construct.pyi:250: error: Expression is of type "coo_array[_ScalarT, tuple[int, int]]", not "coo_array[complex128, tuple[int, int]]"  [assert-type]

randolf-scholz commented Jul 8, 2025

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randolf-scholz commented Jul 8, 2025

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randolf-scholz mentioned this pull request Jul 8, 2025

[CI]: mypy-primer(0) timeout due to long checking of colour #19403

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randolf-scholz commented Jul 9, 2025

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randolf-scholz mentioned this pull request Jul 9, 2025

Unsupported operand types for + ("list[None]" and "list[str]") #19413

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randolf-scholz added 18 commits July 23, 2025 10:19

inital commit

174e1d3

11 failures remain

d753d38

3 test remain

29d5d49

1 check remaining

43eaa3f

checks pass

cfba9a1

some simplifications

c7f73a8

revert fixture modification

fc42098

simplify

a464408

Simplified away early inner_solution computation

af7a962

added testLiteralMappingContext

869a980

replace one hack with another

20de89f

fixed use get_proper_type before isinstance check

9ae652e

added testContextFreeConcatInvariantType and testInContextConcatInvar…

24d8c7b

…iantType

Added test "testTypedDictWideContext".

66f6e7b

updated testBinaryOperatorContext

1db896c

rebased master

451e5cd

ignore joint when no inner constraints

2e62e5f

fix TypedDict with wide context bug

ba9aa63

randolf-scholz force-pushed the solve_intermediate_variable_bug branch from 3e40ab7 to ba9aa63 Compare July 24, 2025 14:09

randolf-scholz mentioned this pull request Aug 1, 2025

meet_types gives unexpected results when meeting literal and Instance #19560

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