tree 2a1204ae0936364136eeb50d12d8d9230fc24d17
parent 2404176d3ca9e3b5543204f1986a8e9b153522a4
author Patrick Williams <patrick@stwcx.xyz> 1637681756 -0600
committer Patrick Williams <patrick@stwcx.xyz> 1638982862 +0000

object: handle diamond inheritance

Commit 664922157bbbd14f0ad1692cee5547f60f6c617c added an inheritance
to `server::object` to gain access to the bus-pointer.  This was
observed to cause a compile failure in some applications which had a
diamond-inheritance structure due to a nested `object` inheritance:

    `object<object<iface0, iface1>, object<iface2, iface3>>`

These clients probably should not have attempted a nested/diamond
because the previous implementation would have resulted in a silent
failure to make `action::emit_interface_added` work properly (since
object itself doesn't have an `emit_added` function).

Improve the `object` so that:
    - Diamond inheritance is no longer possible with nested inherits.
    - The `action::emit_interface_added` action works properly with
      nested inherits.

This required adding some template specialization to determine if one of
the type arguments to `object` were nested (ie.
`object<Args0..., object<Args1...>, Args2...>`) and collapse out the
nested `object` inheritance (so that the example acts exactly the same
as `object<Args0..., Args1..., Args2...>`).

Tested: Enhance the existing `object::emit` test cases to operate on a
nested `object` structure.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I10635a256aafbdc1e42439a49fa61127e06c8e36