I would expect _expand to behave by default like expand-word or list-expand,
but it doesn't.

For example, given default shell options, if `foo=*`, then expand-word and
list-expand will complete `$foo` to `*` and `$~foo` to the files matched by
`*` as a glob expression.

However, no matter what zstyle options I set, _expand will either complete
both of these to `\*` or both of these to the files globbed by `*`.

By default, I would expect _expand to complete expressions in the same way
as the shell substitutes them when evaluating the command line.

Is there a combination of zstyles that makes _expand complete `$foo` to its
literal value and `$~foo` to the files globbed by its value?

If not, then I would like to see this being added somehow and preferably be
made the default behavior.