frozenset() created from a set literal is not untracked by the GC

[aisk]

gh-140232 made frozensets untracked by the GC when none of their elements can be tracked. However, the compiler's fast path for frozenset({...}) and frozenset({... for ...}) freezes the built set in place with _PySet_Freeze() (INTRINSIC_BUILD_FROZENSET), which skips that check, so the result stays tracked:

>>> import gc
>>> s = {1, 2}
>>> gc.is_tracked(frozenset(s))
False
>>> gc.is_tracked(frozenset({1, 2}))
True

I'm preparing a PR for this.

Linked PRs

• gh-155181: Untrack frozensets created from set literals when possible #155182