[ty] sys.implementation.version is not sys.version_info#25608
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Typing conformance resultsNo changes detected ✅Current numbersThe percentage of diagnostics emitted that were expected errors held steady at 92.13%. The percentage of expected errors that received a diagnostic held steady at 87.18%. The number of fully passing files held steady at 92/134. |
Memory usage reportMemory usage unchanged ✅ |
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Merging this PR will not alter performance
Comparing 
Footnotes
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charliermarsh
approved these changes
Jun 3, 2026
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Summary
The way we special-cased
sys.version_infoaccidentally also treatedsys.implementation.versionas always being the Python version, but this is only true for CPython. This was because both are instances ofsys._version_infoclass in typeshed, and our special-casing operated at the level of that class.Adjust things so that class is no longer treated as a singleton, and our special-casing operates at the instance layer rather than the class layer.
This also allows removing the now-unused
ExpandedClassBaseEntry::Syntheticvariant, which allows simplifying some diagnostic code.Closes astral-sh/ty#3640
Testing
Added mdtest.