Hi Juan,

I also use `broadcast_to` a lot, to save memory, but definitely have been in a situation where in another piece of code the array is assumed to be normal and writable (typically, that other piece was also written by me; so much for awareness...). Fortunately, `broadcast_to` already returns read-only views (it is newer and was designed as such from the start), so I was alerted.

At the time `broadcast_to` was introduced [1], there was a discussion about `broadcast_arrays` as well, and it was decided to leave it writable - see the note at https://github.com/numpy/numpy/blob/master/numpy/lib/stride_tricks.py#L265. The same note suggests a deprecation cycle, but like Hameer I don't really see how that helps - there is no way to avoid the warning in the large majority of cases where readonly views are exactly what the user wanted in the first place. So, that argues for cold turkey...

The one alternative would be to actually warn only if one attempts to write to a broadcast array - apparently this has been done for `np.diag` as well [2], so code to do so supposedly exists.

All the best,

Marten

[1] https://github.com/numpy/numpy/pull/5371

[2] https://github.com/numpy/numpy/pull/5371#issuecomment-75238827