Remove cast from implement macro

[sivadeilra]

This is a cleanup item for my PR #3055. That PR (and many others that I submitted around the same time) greatly improved support for creating COM objects. This PR cleans up a few minor things from that work.

First, this PR deletes the generated cast method on types marked with #[implement]. The cast method was an older mechanism for casting from an object to one of its interfaces. It is extremely dangerous because it relies on memory constraints that are not verifiable (which is why it is marked unsafe). My previous PRs provided much better ways to handle the need for this, with the to_interface, as_interface etc. methods. So cast is dangerous and unneeded; let's just remove it. This is a breaking change, but it's needed.

Second, the PR removes an incorrect type bound on a method in ComObject. This is harmless.

[riverar]

This method is currently in the documentation; what's the proposed new API surface here? Are these methods drop-in replacements or?

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

[sivadeilra]

This method is currently in the documentation; what's the proposed new API surface here? Are these methods drop-in replacements or?

There are already better replacements: ComObject::as_interface, ComObject::to_interface. You can see in the existing code where I changed uses of cast() to use these functions. The replacements are safe and do not require runtime type checks (QueryInterface calls).

Which docs reference cast? I can update the docs.

Also, note that this PR is about the T::cast method, not the ComObject::cast method, which is unaffected (and is safe).

[riverar]

Ah, thanks. I also took it for a spin and realized we weren't talking about Interface::cast.

[kennykerr]

Nice, less scary code is great.