Dynamic Invocation

[steipete]

With using objc_msgForward, we can add hooks without offering a type signature.

_ = try testObj.hook(#selector(TestClass.executeBlock)) { bSelf in
  print("Before Interposing Dynamic Hook for \(bSelf)")
}

This is slightly slower than the typed call, but way more convenient

This is achieved with a few tricks:

1. We install the subclass
2. The hooked method gets a super trampoline
3. we add a interpose_origMethod and copy the implementation (which is the super trampoline)
4. change orig impl to objc_msgForward
5. Custom forward handler calls hooks, changes invocation selector to interpose_
6. super handler in interpose changes _cmd back to expected and calls super

TODO:

• class-based not just objects (can't easily fix the selector then...
• pass on invocation + helpers to get parameters
• copy block parameters as needed
• check block type signature
• Generalize interpose _cmd filter

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[crsantos]

Hey Peter, hope you're fine.

Honest question, was there any work left to do on this PR?
Because this would be an awesome feature ❤️