Fix: Support derived class objects in Delegate constructor (#20)

[konard]

Summary

Fixes issue #20 where creating a Delegate with a derived class object and member function pointer would fail during template argument deduction.

Problem

The original constructor template required the object type and member function class type to match exactly:

template <typename Class>
Delegate(std::shared_ptr<Class> object, ReturnType(Class:: *member)(Args...))

This caused compilation errors when using derived class objects with inherited member functions:

struct base { void foo() { std::cout << "foo"; } };
struct derived : public base {};

auto object = std::make_shared<derived>();
auto delegate = Delegate(object, &derived::foo); // Failed - deduced conflicting types for Class

Solution

Modified the constructor to accept separate template parameters for the object type and member function class type:

template <typename ObjectClass, typename MemberClass>
Delegate(std::shared_ptr<ObjectClass> object, ReturnType(MemberClass:: *member)(Args...))
    : Delegate(std::make_shared<MemberMethod<MemberClass>>(std::static_pointer_cast<MemberClass>(object), member)) { }

• Uses std::static_pointer_cast to safely convert the derived object to the base class
• Updated the corresponding template deduction guide
• Maintains backward compatibility with existing code

Test Results

Added comprehensive test cases that verify:

• ✅ Derived objects with base class methods
• ✅ Multi-level inheritance scenarios
• ✅ Return value handling
• ✅ Virtual method polymorphism
• ✅ Base pointer to derived object scenarios

All tests pass, confirming both the fix and backward compatibility.

🤖 Generated with Claude Code

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Resolves #20