[BUG]: annotating argument as list[some_type] raises CompileError

[jbrockmendel]

Trying to add pure-py annotation here

-def append(self, others) -> BlockPlacement:
+def append(self, others: list[BlockPlacement]) -> BlockPlacement:

raises

pandas/_libs/internals.pyx:166:57: Compiler crash in IterationTransform

[da-woods]

I assume this is 0.29.x you're using (although the same bug probably exists on 3.0a)?

Ultimately #3910 should help with this sort of thing (although it currently only looks at the typing module and doesn't make the built-in types subscriptable; that's probably a fairly easy change for the future though).

For the moment Cython's unlikely to use the [BlockPlacement] information, so one solution would be to omit that. Obviously you may want it for your own documentation though.

I imagine the likely outcome is that 0.29.x will end up treating this as object (but not crashing) but at some point 3.0x will recognise it correctly as list.

[jbrockmendel]

I assume this is 0.29.x you're using (although the same bug probably exists on 3.0a)?

ive only tried this on 0.29.23

For the moment Cython's unlikely to use the [BlockPlacement] information, so one solution would be to omit that. Obviously you may want it for your own documentation though.

yah, this is basically cosmetic in this context

[da-woods]

FWIW this was a duplicate of #2811. It looks like that didn't get backported. I've created a PR with a minimal bit backported, but it's possible that this isn't the cleanest way to fix it.

No longer true - it's probably best to just backport the whole thing