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Title: RFC: Rework `*args` parsing by randolf-scholz · Pull Request #20472 · python/mypy · GitHub

Open Graph Title: RFC: Rework `*args` parsing by randolf-scholz · Pull Request #20472 · python/mypy

X Title: RFC: Rework `*args` parsing by randolf-scholz · Pull Request #20472 · python/mypy

Description: Optional static typing for Python. Contribute to python/mypy development by creating an account on GitHub.

Open Graph Description: Apologies in advance for this monster PR. This is based on #19651, which had a flaw discovered in #19651 (comment), that turned out to be lethal for the approach taken. It turns out we need much mo...

X Description: Apologies in advance for this monster PR. This is based on #19651, which had a flaw discovered in #19651 (comment), that turned out to be lethal for the approach taken. It turns out we need much mo...

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RFC: Rework *args parsinghttps://github.com/python/mypy/pull/20472#top
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Dec 25, 2025https://github.com/python/mypy/pull/20472#issue-3761820011
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#19651https://github.com/python/mypy/pull/19651
#19651 (comment)https://github.com/python/mypy/pull/19651#issuecomment-3193885899
type inference failure on custom iterable class unpacking #20435https://github.com/python/mypy/issues/20435
Inconsistent constraint resolution for tuples. #19860https://github.com/python/mypy/issues/19860
Bad interaction between ParamSpec and TypeVarTuple #19855https://github.com/python/mypy/issues/19855
Incorrect mapping of actual to formal arguments. #19692https://github.com/python/mypy/issues/19692
mypy doesn't understand that *args: P.args implies that args is a tuple #19663https://github.com/python/mypy/issues/19663
mypy fails to correctly understand some iterable type in *args #19662https://github.com/python/mypy/issues/19662
Mypy fails to solve tuple[int, *Ts, int] as an Iterable[T]. #19659https://github.com/python/mypy/issues/19659
[1.14 regression] Unpacking an iterator converts the inner type to Any #18320https://github.com/python/mypy/issues/18320
Variadic *args where args: Union[Tuple[...], Tuple[...], ...] are _never_ checked [False Negative] #17161https://github.com/python/mypy/issues/17161
Unpacking unions of tuples skips type checking #15969https://github.com/python/mypy/issues/15969
Unpacking an iterable in a list comprehension leads to the type inferred as list[Any] #15747https://github.com/python/mypy/issues/15747
Custom __iter__ method yields false positive when used with star args (*) #14470https://github.com/python/mypy/issues/14470
False-positive with multiple *args splats in a function call #10481https://github.com/python/mypy/issues/10481
"multiple values for keyword argument" with star expansion #6799https://github.com/python/mypy/issues/6799
Can't infer tuple inside match case #18039https://github.com/python/mypy/issues/18039
open problemshttps://github.com/python/mypy/pull/20472#open-problems
Overridden __iter__ with more specific item type is only respected in some contexts #16492https://github.com/python/mypy/issues/16492
https://mypy-play.net/?mypy=latest&python=3.12&gist=82739825de042dfeea487d83823d11bdhttps://mypy-play.net/?mypy=latest&python=3.12&gist=82739825de042dfeea487d83823d11bd
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https://mypy-play.net/?mypy=latest&python=3.12&gist=2be305f25ddbea0fc37f02b319a2d90dhttps://mypy-play.net/?mypy=latest&python=3.12&gist=2be305f25ddbea0fc37f02b319a2d90d
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Incorrect mapping of actual to formal arguments. #19692 (comment)https://github.com/python/mypy/issues/19692#issuecomment-3238851841
AnyOf - Union for return types typing#566https://github.com/python/typing/issues/566
Inconsistent constraint resolution for tuples. #19860 (comment)https://github.com/python/mypy/issues/19860#issuecomment-3297377452
Overridden __iter__ with more specific item type is only respected in some contexts #16492https://github.com/python/mypy/issues/16492
tuple index out of range error is inconsistent #20475https://github.com/python/mypy/issues/20475
tuple[Any, *tuple[Any, ...]] is not assignable to other tuple types #19109https://github.com/python/mypy/issues/19109
Lenient TypeVarTuple checking when number of dimensions is unknown #18665https://github.com/python/mypy/issues/18665
Inconsistent constraint resolution for tuples. #19860https://github.com/python/mypy/issues/19860
Inconsistent constraint resolution for tuples. #19860https://github.com/python/mypy/issues/19860
mypy doesn't understand that *args: P.args implies that args is a tuple #19663https://github.com/python/mypy/issues/19663
Incorrect mapping of actual to formal arguments. #19692https://github.com/python/mypy/issues/19692
Bad interaction between ParamSpec and TypeVarTuple #19855https://github.com/python/mypy/issues/19855
Incorrect mapping of actual to formal arguments. #19692https://github.com/python/mypy/issues/19692
Inconsistent constraint resolution for tuples. #19860https://github.com/python/mypy/issues/19860
Incorrect mapping of actual to formal arguments. #19692https://github.com/python/mypy/issues/19692
Incorrect mapping of actual to formal arguments. #19692https://github.com/python/mypy/issues/19692
mypy fails to correctly understand some iterable type in *args #19662https://github.com/python/mypy/issues/19662
Incorrect mapping of actual to formal arguments. #19692https://github.com/python/mypy/issues/19692
Inconsistent constraint resolution for tuples. #19860https://github.com/python/mypy/issues/19860
Please reload this pagehttps://github.com/python/mypy/pull/20472
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December 25, 2025 11:12https://github.com/python/mypy/pull/20472#commits-pushed-7db048d
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fixed but with tuple from Anyhttps://github.com/python/mypy/pull/20472/commits/06f12c00bcfa10fd2fc4f78f52d8fdd4403dafeb
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Dec 25, 2025 https://github.com/python/mypy/pull/20472#ref-issue-3761820632
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Dec 26, 2025 https://github.com/python/mypy/pull/20472#ref-issue-3762968034
tuple index out of range error is inconsistent #20475 https://github.com/python/mypy/issues/20475
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Dec 26, 2025https://github.com/python/mypy/pull/20472#issuecomment-3692451479
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tuple index out of range error is inconsistent #20475https://github.com/python/mypy/issues/20475
tuple[Any, *tuple[Any, ...]] is not assignable to other tuple types #19109https://github.com/python/mypy/issues/19109
Lenient TypeVarTuple checking when number of dimensions is unknown #18665https://github.com/python/mypy/issues/18665
Please reload this pagehttps://github.com/python/mypy/pull/20472
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added fast path for tuple[Any, ...] comparisonhttps://github.com/python/mypy/pull/20472/commits/024cf4963b837cd9f78ed0ad3f46061e953a89b8
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Jan 2, 2026 https://github.com/python/mypy/pull/20472#ref-pullrequest-3318286131
Rework starargs with union argument #19651 https://github.com/python/mypy/pull/19651
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Jan 16, 2026 https://github.com/python/mypy/pull/20472#ref-issue-3809565816
Misleading error message with dict.get like method. (polymorphic function with conflicting context) #20576 https://github.com/python/mypy/issues/20576
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Mar 8, 2026 https://github.com/python/mypy/pull/20472#ref-pullrequest-3149539966
Remove list.__add__ overloads. python/typeshed#14282 https://github.com/python/typeshed/pull/14282
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Apr 7, 2026 https://github.com/python/mypy/pull/20472#ref-pullrequest-4196809054
Fix regression involving dict or on recursive dict #21148 https://github.com/python/mypy/pull/21148
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Unpacking unions of tuples skips type checking https://github.com/python/mypy/issues/15969
Unpacking an iterable in a list comprehension leads to the type inferred as list[Any] https://github.com/python/mypy/issues/15747
Custom __iter__ method yields false positive when used with star args (*) https://github.com/python/mypy/issues/14470
False-positive with multiple *args splats in a function call https://github.com/python/mypy/issues/10481
"multiple values for keyword argument" with star expansion https://github.com/python/mypy/issues/6799
Overridden __iter__ with more specific item type is only respected in some contexts https://github.com/python/mypy/issues/16492
Variadic *args where args: Union[Tuple[...], Tuple[...], ...] are _never_ checked [False Negative] https://github.com/python/mypy/issues/17161
Can't infer tuple inside match case https://github.com/python/mypy/issues/18039
[1.14 regression] Unpacking an iterator converts the inner type to Any https://github.com/python/mypy/issues/18320
Mypy fails to solve tuple[int, *Ts, int] as an Iterable[T]. https://github.com/python/mypy/issues/19659
Please reload this pagehttps://github.com/python/mypy/pull/20472
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