🚀 The feature, motivation and pitch

There are several issues with the current type hints for torch.Size:

It simply subclasses tuple[int, ...], but this causes several typing errors, for example:

import torch
x = torch.Size([1,2,3])
y = torch.Size([4,5,6])
reveal_type(x+y)  # tuple[int, ...], not Size !!!

This is because tuple.__add__ is annotated to return tuple.

Alternatives

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Additional context

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cc @ezyang @malfet @xuzhao9 @gramster