if it was generated from a :class:`.Column` that didn't specify ``unique``
(where it defaults to ``None``).  The flag will now always be ``True`` or
``False``. [ticket:2825]

mssql to ensure that any literal SQL expression values are
rendered directly as literals, instead of as bound parameters,
within a CREATE INDEX statement. [ticket:2742]
- don't need expression_as_ddl(); literal_binds and include_table
take care of this functionality.

or object method as an argument, in addition to a standalone function;
will properly detect if the "context" argument is accepted or not.

events are called, so that attachment events can be used to dynamically
generate a name for the index based on the parent table and/or
columns. [ticket:2835]

typically via in-place mutation, will raise an informative error
message rather than causing a recursion overflow.
[ticket:2815]

:func:`.foreign` on a :class:`.Column` before association with a parent
:class:`.Table` could produce issues related to the parent table not
rendering within joins, due to the inherent copy operation performed
by an annotation. [ticket:2813]

name is already an instance of _anonymous_label(), we don't downgrade
it to a plain quoted_name - fixes regression from [ticket:2812].
[ticket:2834]