x.copy_(y) doesn't work with sparse x #8330
Description
>>> i = torch.LongTensor([[0, 2], [1, 0], [1, 2]])
>>> v = torch.FloatTensor([3, 4, 5 ])
>>> x = torch.sparse.FloatTensor(i.t(), v, torch.Size([2,3]))
>>> x2 = torch.sparse.FloatTensor(i.t(), v, torch.Size([2,3]))
>>> x.copy_(x2)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
RuntimeError: copy does not support torch.sparse.FloatTensor to torch.sparse.FloatTensor copy.
There isn't really any reason this shouldn't work; internally we have all the pieces implemented already.