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[ty] Ban multiple unpacked variadic tuples in a tuple specialization#22884

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AlexWaygood merged 2 commits intomainfrom
alex/two-starred-tuples
Jan 27, 2026
Merged

[ty] Ban multiple unpacked variadic tuples in a tuple specialization#22884
AlexWaygood merged 2 commits intomainfrom
alex/two-starred-tuples

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@AlexWaygood AlexWaygood commented Jan 27, 2026 •
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Summary

The spec states that while this is allowed:

tuple[*tuple[int, ...], *tuple[str]]

and this is allowed:

from typing import TypeVarTuple

Ts = TypeVarTuple("Ts")

tuple[*Ts, *tuple[str]]

none of these are, because multiple variadic tuples cannot be unpacked in the context of a single tuple specialization:

tuple[*tuple[int, ...], *tuple[str, ...]]
tuple[*tuple[int, ...], str, *tuple[bytes, ...]]
tuple[*Ts, *Ts]
tuple[*Ts, *tuple[int, ...]]

This PR adds the missing diagnostics.

Test Plan

snapshots and mdtests

@AlexWaygood AlexWaygood added the ty Multi-file analysis & type inference label Jan 27, 2026
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astral-sh-bot bot commented Jan 27, 2026 •
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Typing conformance results improved 🎉

The percentage of diagnostics emitted that were expected errors increased from 78.84% to 78.95%. The percentage of expected errors that received a diagnostic increased from 69.42% to 69.88%.

Summary

Metric Old New Diff Outcome
True Positives 749 754 +5 ⏫ (✅)
False Positives 201 201 +0
False Negatives 330 325 -5 ⏬ (✅)
Total Diagnostics 950 955 +5 ⏫
Precision 78.84% 78.95% +0.11% ⏫ (✅)
Recall 69.42% 69.88% +0.46% ⏫ (✅)

True positives added

Details
Location Name Message
generics_typevartuple_specialization.py:121:7 invalid-type-form Multiple unpacked variadic tuples are not allowed in a tuple specialization
generics_typevartuple_specialization.py:122:7 invalid-type-form Multiple unpacked variadic tuples are not allowed in a tuple specialization
tuples_unpacked.py:40:5 invalid-type-form Multiple unpacked variadic tuples are not allowed in a tuple specialization
tuples_unpacked.py:41:5 invalid-type-form Multiple unpacked variadic tuples are not allowed in a tuple specialization
tuples_unpacked.py:51:9 invalid-type-form Multiple unpacked variadic tuples are not allowed in a tuple specialization

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astral-sh-bot bot commented Jan 27, 2026 •
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mypy_primer results

Changes were detected when running on open source projects 
scikit-build-core (https://github.com/scikit-build/scikit-build-core)
+ src/scikit_build_core/build/wheel.py:99:20: error[no-matching-overload] No overload of bound method `__init__` matches arguments
- Found 46 diagnostics
+ Found 47 diagnostics

core (https://github.com/home-assistant/core)
+ homeassistant/util/variance.py:47:12: error[invalid-return-type] Return type does not match returned value: expected `(**_P@ignore_variance) -> _R@ignore_variance`, found `_Wrapped[_P@ignore_variance, int | _R@ignore_variance | float | datetime, _P@ignore_variance, _R@ignore_variance | int | float | datetime]`
- Found 14488 diagnostics
+ Found 14489 diagnostics

No memory usage changes detected ✅

@AlexWaygood AlexWaygood force-pushed the alex/two-starred-tuples branch 2 times, most recently from 7cfca5a to 9dd669f Compare January 27, 2026 14:32
@AlexWaygood AlexWaygood changed the title [ty] Ban multiple starred expressions in a tuple specializatoin [ty] Ban multiple unpacked variadic tuples in a tuple specialization Jan 27, 2026
@AlexWaygood AlexWaygood marked this pull request as ready for review January 27, 2026 14:36
@AlexWaygood AlexWaygood force-pushed the alex/two-starred-tuples branch from 9dd669f to 54beb29 Compare January 27, 2026 14:41
@AlexWaygood AlexWaygood mentioned this pull request Jan 27, 2026
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carljm
carljm approved these changes Jan 27, 2026
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crates/ty_python_semantic/src/types/infer/builder/type_expression.rs Outdated
diagnostic.annotate(
self.context
.secondary(element)
.message("Second unpacked variadict tuple"),
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Suggested change
.message("Second unpacked variadict tuple"),
.message("Second unpacked variadic tuple"),

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@AlexWaygood AlexWaygood Jan 27, 2026 •
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beat you to it :P

@AlexWaygood AlexWaygood enabled auto-merge (squash) January 27, 2026 16:42
@AlexWaygood AlexWaygood merged commit 72fd386 into main Jan 27, 2026
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@AlexWaygood AlexWaygood deleted the alex/two-starred-tuples branch January 27, 2026 16:44
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@carljm carljm carljm approved these changes

@sharkdp sharkdp Awaiting requested review from sharkdp sharkdp is a code owner

@dcreager dcreager Awaiting requested review from dcreager dcreager is a code owner

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@AlexWaygood @carljm