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[mypyc] Avoid polluting generator environment layouts - #21990
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When setting up a non-merged generator, we passed the generator helper symbol table to load_outer_env. This made the closure environment class inherit the helper arguments and generator state as attributes, adding six unused object slots to every affected environment. It could also replace the declared type of the environment self-reference with the generator frame type. Load the outer environment directly from the generator frame during setup, and make load_outer_env copy only attributes that are actually owned by the environment being loaded. Add a regression test that verifies helper-only attributes stay out of the environment and that its self-reference keeps the correct type.
p-sawicki
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Sep 15, 2026
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BTW, from now on I won't mention if I used coding agent assist explicitly, unless perhaps a PR was 100% created using a coding agent, with minimal direct involvement from me. These days I'm using coding agents in most PRs (often multiple agents/models). |
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When setting up a non-merged generator, we passed the generator helper symbol table to load_outer_env. This made the closure environment class inherit the helper arguments and generator state as attributes, adding six unused object slots to every affected environment.
Load the outer environment directly from the generator frame during setup, and make load_outer_env copy only attributes that are actually owned by the environment being loaded. Add a regression test that verifies helper-only attributes stay out of the environment and that its self-reference keeps the correct type.
This made a few microbenchmarks that allocate lots of generators noticeably (though not massively) faster.