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Aug 4, 2025
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Remove --new-type-inference flag #19570

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10 changes: 0 additions & 10 deletions mypy/main.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1092,10 +1092,6 @@ def add_invertible_flag(
internals_group.add_argument(
"--old-type-inference", action="store_true", help=argparse.SUPPRESS
)
# Deprecated reverse variant of the above.
internals_group.add_argument(
"--new-type-inference", action="store_true", help=argparse.SUPPRESS
)
internals_group.add_argument(
"--disable-expression-cache", action="store_true", help=argparse.SUPPRESS
)
Expand Down Expand Up @@ -1487,12 +1483,6 @@ def set_strict_flags() -> None:
if options.logical_deps:
options.cache_fine_grained = True

if options.new_type_inference:
print(
"Warning: --new-type-inference flag is deprecated;"
" new type inference algorithm is already enabled by default"
)

if options.strict_concatenate and not strict_option_set:
print("Warning: --strict-concatenate is deprecated; use --extra-checks instead")

Expand Down
4 changes: 1 addition & 3 deletions mypy/options.py
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Original file line number Diff line number Diff line change
Expand Up @@ -391,10 +391,8 @@ def __init__(self) -> None:
# skip most errors after this many messages have been reported.
# -1 means unlimited.
self.many_errors_threshold = defaults.MANY_ERRORS_THRESHOLD
# Disable new experimental type inference algorithm.
# Disable new type inference algorithm.
self.old_type_inference = False
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Do we still need this one? There are only a couple of use sites remaining, maybe just axe them here?

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Yeah, no, I think we may keep it for a while more (just in case), since it is not a no-op, unlike --new-type-inference.

# Deprecated reverse version of the above, do not use.
self.new_type_inference = False
# Disable expression cache (for debugging).
self.disable_expression_cache = False
# Export line-level, limited, fine-grained dependency information in cache data
Expand Down
35 changes: 0 additions & 35 deletions test-data/unit/check-generics.test
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Original file line number Diff line number Diff line change
Expand Up @@ -2750,7 +2750,6 @@ reveal_type(func(1)) # N: Revealed type is "builtins.int"
[builtins fixtures/tuple.pyi]

[case testGenericLambdaGenericMethodNoCrash]
# flags: --new-type-inference
from typing import TypeVar, Union, Callable, Generic

S = TypeVar("S")
Expand Down Expand Up @@ -2789,7 +2788,6 @@ reveal_type(dict2) # N: Revealed type is "builtins.dict[Any, __main__.B]"
-- ------------------------------------------------------------------

[case testInferenceAgainstGenericCallable]
# flags: --new-type-inference
from typing import TypeVar, Callable, List

X = TypeVar('X')
Expand All @@ -2807,7 +2805,6 @@ reveal_type(bar(id)) # N: Revealed type is "builtins.list[builtins.int]"
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericCallableNoLeak]
# flags: --new-type-inference
from typing import TypeVar, Callable

T = TypeVar('T')
Expand All @@ -2823,7 +2820,6 @@ reveal_type(f(tpl)) # N: Revealed type is "Any"
[out]

[case testInferenceAgainstGenericCallableChain]
# flags: --new-type-inference
from typing import TypeVar, Callable, List

X = TypeVar('X')
Expand All @@ -2836,7 +2832,6 @@ reveal_type(chain(id, id)) # N: Revealed type is "def (builtins.int) -> builtin
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericCallableGeneric]
# flags: --new-type-inference
from typing import TypeVar, Callable, List

S = TypeVar('S')
Expand All @@ -2857,7 +2852,6 @@ reveal_type(same(42)) # N: Revealed type is "builtins.list[builtins.int]"
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericCallableGenericReverse]
# flags: --new-type-inference
from typing import TypeVar, Callable, List

S = TypeVar('S')
Expand All @@ -2878,7 +2872,6 @@ reveal_type(same([42])) # N: Revealed type is "builtins.int"
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericCallableGenericArg]
# flags: --new-type-inference
from typing import TypeVar, Callable, List

S = TypeVar('S')
Expand All @@ -2899,7 +2892,6 @@ reveal_type(single(42)) # N: Revealed type is "builtins.list[builtins.int]"
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericCallableGenericChain]
# flags: --new-type-inference
from typing import TypeVar, Callable, List

S = TypeVar('S')
Expand All @@ -2913,7 +2905,6 @@ reveal_type(comb(id, id)) # N: Revealed type is "def [T] (T`1) -> T`1"
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericCallableGenericNonLinear]
# flags: --new-type-inference
from typing import TypeVar, Callable, List

S = TypeVar('S')
Expand All @@ -2934,7 +2925,6 @@ reveal_type(mix([id, id, id])) # N: Revealed type is "def [S] (S`4) -> builtins
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericCurry]
# flags: --new-type-inference
from typing import Callable, List, TypeVar

S = TypeVar("S")
Expand All @@ -2953,7 +2943,6 @@ reveal_type(dec2(test2)) # N: Revealed type is "def [T] (T`3) -> def (T`3) -> T
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericCallableNewVariable]
# flags: --new-type-inference
from typing import TypeVar, Callable, List

S = TypeVar('S')
Expand All @@ -2968,7 +2957,6 @@ reveal_type(dec(test)) # N: Revealed type is "def [U] (builtins.list[U`-1]) ->
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericCallableGenericAlias]
# flags: --new-type-inference
from typing import TypeVar, Callable, List

S = TypeVar('S')
Expand All @@ -2986,7 +2974,6 @@ reveal_type(dec(id)) # N: Revealed type is "def [S] (S`1) -> builtins.list[S`1]
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericCallableGenericProtocol]
# flags: --new-type-inference
from typing import TypeVar, Protocol, Generic, Optional

T = TypeVar('T')
Expand All @@ -3002,7 +2989,6 @@ reveal_type(lift(g)) # N: Revealed type is "def [T] (Union[T`1, None]) -> Union
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericSplitOrder]
# flags: --new-type-inference
from typing import TypeVar, Callable, List

S = TypeVar('S')
Expand All @@ -3017,7 +3003,6 @@ reveal_type(dec(id, id)) # N: Revealed type is "def (builtins.int) -> builtins.
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericSplitOrderGeneric]
# flags: --new-type-inference
from typing import TypeVar, Callable, Tuple

S = TypeVar('S')
Expand Down Expand Up @@ -3048,7 +3033,6 @@ reveal_type(id) # N: Revealed type is "def (builtins.int) -> builtins.int"
[builtins fixtures/tuple.pyi]

[case testInferenceAgainstGenericEllipsisSelfSpecialCase]
# flags: --new-type-inference
from typing import Self, Callable, TypeVar

T = TypeVar("T")
Expand All @@ -3062,7 +3046,6 @@ c: C
reveal_type(c.test()) # N: Revealed type is "__main__.C"

[case testInferenceAgainstGenericBoundsAndValues]
# flags: --new-type-inference
from typing import TypeVar, Callable, List

class B: ...
Expand Down Expand Up @@ -3090,7 +3073,6 @@ reveal_type(dec2(id2)) # N: Revealed type is "def (Never) -> builtins.list[Neve
# E: Argument 1 to "dec2" has incompatible type "Callable[[V], V]"; expected "Callable[[Never], Never]"

[case testInferenceAgainstGenericLambdas]
# flags: --new-type-inference
from typing import TypeVar, Callable, List

S = TypeVar('S')
Expand Down Expand Up @@ -3127,7 +3109,6 @@ dec4_bound(lambda x: x) # E: Value of type variable "I" of "dec4_bound" cannot
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericParamSpecBasicInList]
# flags: --new-type-inference
from typing import TypeVar, Callable, List, Tuple
from typing_extensions import ParamSpec

Expand All @@ -3146,7 +3127,6 @@ reveal_type(dec(pair)) # N: Revealed type is "def [U, V] (x: U`-1, y: V`-2) ->
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericParamSpecBasicDeList]
# flags: --new-type-inference
from typing import TypeVar, Callable, List, Tuple
from typing_extensions import ParamSpec

Expand All @@ -3163,7 +3143,6 @@ reveal_type(dec(either)) # N: Revealed type is "def [T] (x: builtins.list[T`5],
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericParamSpecPopOff]
# flags: --new-type-inference
from typing import TypeVar, Callable, List, Tuple
from typing_extensions import ParamSpec, Concatenate

Expand All @@ -3184,7 +3163,6 @@ reveal_type(dec(dec)) # N: Revealed type is "def () -> def [T, P, S] (def (T`-1
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericParamSpecPopOn]
# flags: --new-type-inference
from typing import TypeVar, Callable, List, Tuple
from typing_extensions import ParamSpec, Concatenate

Expand All @@ -3206,7 +3184,6 @@ reveal_type(dec(dec)) # N: Revealed type is "def [T, S] (T`13, f: def () -> def
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericParamSpecVsParamSpec]
# flags: --new-type-inference
from typing import TypeVar, Callable, List, Tuple, Generic
from typing_extensions import ParamSpec, Concatenate

Expand All @@ -3227,7 +3204,6 @@ reveal_type(dec(h)) # N: Revealed type is "def [T, Q] (T`-1, *Q.args, **Q.kwarg
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericParamSpecVsParamSpecConcatenate]
# flags: --new-type-inference
from typing import TypeVar, Callable, List, Tuple, Generic
from typing_extensions import ParamSpec, Concatenate

Expand All @@ -3245,7 +3221,6 @@ reveal_type(dec(h)) # N: Revealed type is "def [T, Q] (T`-1, *Q.args, **Q.kwarg
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericParamSpecSecondary]
# flags: --new-type-inference
from typing import TypeVar, Callable, List, Tuple, Generic
from typing_extensions import ParamSpec, Concatenate

Expand All @@ -3263,7 +3238,6 @@ reveal_type(dec(g)) # N: Revealed type is "def (builtins.int) -> __main__.Foo[[
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericParamSpecSecondOrder]
# flags: --new-type-inference
from typing import TypeVar, Callable
from typing_extensions import ParamSpec, Concatenate

Expand All @@ -3285,7 +3259,6 @@ reveal_type(transform(dec2)) # N: Revealed type is "def [W, T] (def (builtins.i
[builtins fixtures/tuple.pyi]

[case testNoAccidentalVariableClashInNestedGeneric]
# flags: --new-type-inference
from typing import TypeVar, Callable, Generic, Tuple

T = TypeVar('T')
Expand All @@ -3302,7 +3275,6 @@ def apply(a: S, b: T) -> None:
[builtins fixtures/tuple.pyi]

[case testInferenceAgainstGenericParamSpecSpuriousBoundsNotUsed]
# flags: --new-type-inference
from typing import TypeVar, Callable, Generic
from typing_extensions import ParamSpec, Concatenate

Expand All @@ -3321,7 +3293,6 @@ reveal_type(test) # N: Revealed type is "def () -> def [Q] (__main__.Foo[Q`-1])
[builtins fixtures/tuple.pyi]

[case testInferenceAgainstGenericVariadicBasicInList]
# flags: --new-type-inference
from typing import Tuple, TypeVar, List, Callable
from typing_extensions import Unpack, TypeVarTuple

Expand All @@ -3341,7 +3312,6 @@ reveal_type(dec(pair)) # N: Revealed type is "def [U, V] (U`-1, V`-2) -> builti
[builtins fixtures/tuple.pyi]

[case testInferenceAgainstGenericVariadicBasicDeList]
# flags: --new-type-inference
from typing import Tuple, TypeVar, List, Callable
from typing_extensions import Unpack, TypeVarTuple

Expand All @@ -3359,7 +3329,6 @@ reveal_type(dec(either)) # N: Revealed type is "def [T] (builtins.list[T`5], bu
[builtins fixtures/tuple.pyi]

[case testInferenceAgainstGenericVariadicPopOff]
# flags: --new-type-inference
from typing import TypeVar, Callable, List, Tuple
from typing_extensions import Unpack, TypeVarTuple

Expand All @@ -3381,7 +3350,6 @@ reveal_type(dec(dec)) # N: Revealed type is "def () -> def [T, Ts, S] (def (T`-
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericVariadicPopOn]
# flags: --new-type-inference
from typing import TypeVar, Callable, List, Tuple
from typing_extensions import Unpack, TypeVarTuple

Expand All @@ -3404,7 +3372,6 @@ reveal_type(dec(dec)) # N: Revealed type is "def [T, S] (T`13, def () -> def (T
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericVariadicVsVariadic]
# flags: --new-type-inference
from typing import TypeVar, Callable, List, Generic
from typing_extensions import Unpack, TypeVarTuple

Expand All @@ -3424,7 +3391,6 @@ reveal_type(dec(g)) # N: Revealed type is "def [Ts] (*Unpack[Ts`4]) -> builtins
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericVariadicVsVariadicConcatenate]
# flags: --new-type-inference
from typing import TypeVar, Callable, Generic
from typing_extensions import Unpack, TypeVarTuple

Expand All @@ -3443,7 +3409,6 @@ reveal_type(dec(h)) # N: Revealed type is "def [T, Us] (T`-1, *Unpack[Us`-2]) -
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericVariadicSecondary]
# flags: --new-type-inference
from typing import TypeVar, Callable, Generic
from typing_extensions import Unpack, TypeVarTuple

Expand Down
1 change: 0 additions & 1 deletion test-data/unit/check-inference-context.test
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Expand Up @@ -693,7 +693,6 @@ f(lambda: None)
g(lambda: None)

[case testIsinstanceInInferredLambda]
# flags: --new-type-inference
from typing import TypeVar, Callable, Optional
T = TypeVar('T')
S = TypeVar('S')
Expand Down
2 changes: 0 additions & 2 deletions test-data/unit/check-inference.test
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Expand Up @@ -1405,14 +1405,12 @@ class B: pass
[builtins fixtures/list.pyi]

[case testUninferableLambda]
# flags: --new-type-inference
from typing import TypeVar, Callable
X = TypeVar('X')
def f(x: Callable[[X], X]) -> X: pass
y = f(lambda x: x) # E: Need type annotation for "y"

[case testUninferableLambdaWithTypeError]
# flags: --new-type-inference
from typing import TypeVar, Callable
X = TypeVar('X')
def f(x: Callable[[X], X], y: str) -> X: pass
Expand Down
1 change: 0 additions & 1 deletion test-data/unit/check-overloading.test
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Expand Up @@ -6637,7 +6637,6 @@ reveal_type(Snafu.snafu('123')) # N: Revealed type is "builtins.str"
[builtins fixtures/staticmethod.pyi]

[case testOverloadedWithInternalTypeVars]
# flags: --new-type-inference
import m

[file m.pyi]
Expand Down
4 changes: 0 additions & 4 deletions test-data/unit/check-parameter-specification.test
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Expand Up @@ -1121,7 +1121,6 @@ reveal_type(jf(1)) # N: Revealed type is "None"
[builtins fixtures/paramspec.pyi]

[case testGenericsInInferredParamspecReturn]
# flags: --new-type-inference
from typing import Callable, TypeVar, Generic
from typing_extensions import ParamSpec

Expand Down Expand Up @@ -1646,7 +1645,6 @@ def f(f: Callable[P, None], *args: P.args, **kwargs: P.kwargs) -> None: ...
[builtins fixtures/paramspec.pyi]

[case testParamSpecDecoratorAppliedToGeneric]
# flags: --new-type-inference
from typing import Callable, List, TypeVar
from typing_extensions import ParamSpec

Expand Down Expand Up @@ -1684,7 +1682,6 @@ reveal_type(test(*ints)) # N: Revealed type is "__main__.Foo[[*builtins.int]]"
[builtins fixtures/paramspec.pyi]

[case testParamSpecArgumentParamInferenceGeneric]
# flags: --new-type-inference
from typing import Callable, TypeVar
from typing_extensions import ParamSpec

Expand All @@ -1702,7 +1699,6 @@ y: int = call(identity, 2)
[builtins fixtures/paramspec.pyi]

[case testParamSpecNestedApplyNoCrash]
# flags: --new-type-inference
from typing import Callable, TypeVar
from typing_extensions import ParamSpec

Expand Down
1 change: 0 additions & 1 deletion test-data/unit/check-plugin-attrs.test
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Expand Up @@ -1201,7 +1201,6 @@ class A:
[builtins fixtures/bool.pyi]

[case testAttrsFactoryBadReturn]
# flags: --new-type-inference
import attr
def my_factory() -> int:
return 7
Expand Down
1 change: 0 additions & 1 deletion test-data/unit/check-typevar-tuple.test
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Expand Up @@ -886,7 +886,6 @@ reveal_type(z) # N: Revealed type is "tuple[builtins.int, Unpack[builtins.tuple
[builtins fixtures/tuple.pyi]

[case testInferenceAgainstGenericVariadicWithBadType]
# flags: --new-type-inference
from typing import TypeVar, Callable, Generic
from typing_extensions import Unpack, TypeVarTuple

Expand Down
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