[Numpy-discussion] Warn or immidiately change readonly flag on broadcast_arrays return value?

In PR 12609 https://github.com/numpy/numpy/pull/12609 I added code to emit a DepricationWarning when broadcast_arrays returns an array where the output is repeated. While this is a minimal fix to the problem, perhaps we should consider making the output readonly immediately instead? - A deprecation cycle requires two changes to downstream user's code: one to filter the deprecation warning, and another when we actually make the change - Writing to the repeated data will cause errors now. What do you think, should we change the behaviour at all, and if so should we depricate it over two releases or change it immediately? The original issue is here https://github.com/numpy/numpy/issues/2705 Matti