Fix copy.replace widening a bound TypeVar to its bound#15997
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apoorva-01 wants to merge 2 commits into
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Fix copy.replace widening a bound TypeVar to its bound#15997apoorva-01 wants to merge 2 commits into
apoorva-01 wants to merge 2 commits into
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The covariant protocol from python#14786 loses a bound TypeVar whose __replace__ returns Self (dataclasses, namedtuples). Add a Self overload that keeps the argument's type, falling back to the covariant one so Box[int] -> Box[str] still works.
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Fixes #15973
copy.replacedrops a boundTypeVarwhen__replace__returnsSelf, soreplace(config: T, ...)comes back as the bound instead ofT.#14786 made the protocol covariant for the
Box[int] -> Box[str]case, which broke this one. Rather than pick between them, I added a Self-returning overload first that keepsT; anything likeBoxfalls through to the covariant overload. Both work now, and the new test cases fail without it.(#14819 touches the same stub, so one of us will need a rebase.)