3ec889816 changed cell::make_collection() to take different code paths
depending whether its `data` argument is nothrow copyable/movable or
not. In case it is not, it is wrapped in a view to make it so (see the
above mentioned commit for a full explanation), relying on the methods
pre-existing requirement for callers to keep `data` alive while the
created writer is in use.
On closer look however it turns out that this requirement is neither
respected, nor enforced, at least not on the code level. The real
requirement is that the underlying data represented by `data` is kept
alive. If `data` is a view, it is not expected to be kept alive and
callers don't, it is instead copied into `make_collection()`.
Non-views however *are* expected to be kept alive. This makes the API
error prone.
To avoid any future errors due to this ambiguity, require all `data`
arguments to be nothrow copyable and movable. Callers are now required
to pass views of nonconforming objects.
This patch is a usability improvement and is not fixing a bug. The
current code works as-is because it happens to conform to the underlying
requirements.
Refs: #5575
Refs: #5341
Tests: unit(dev)
Signed-off-by: Botond Dénes <bdenes@scylladb.com>
Message-Id: <20200115084520.206947-1-bdenes@scylladb.com>
0c52c2ba50