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#include <iostream>
using namespace std;
 
class FeaturesExample {};
class Example : public FeaturesExample {};
 
template<typename D>
class Base {
 public:
  virtual float getFloat(const typename D::ExampleType* ex) const = 0;
  float getFloat(const FeaturesExample& ex) const {
  	get(reinterpret_cast<typename D::ExampleType>(&ex));
  }
  float (Base::*getFloatImplPtr_)(const FeaturesExample& ex) const;
  float getFloatImpl_(const FeaturesExample& ex) const {
  	return 0.0;
  }
};
 
class Derived : public Base<Derived> {
 public:
  typedef ExampleType = Example;
  virtual float getFloatImpl(const Example* ex) override {
  	return 1.0;
  }
};
int main() {
	FeaturesExample ex;
	Derived derived;
	auto f = derived.getFloat(ex);
	std::cout << f << std::endl;
	return 0;
}

prog.cpp: In instantiation of ‘class Base<Derived>’:
prog.cpp:20:24:   required from here
prog.cpp:10:17: error: invalid use of incomplete type ‘class Derived’
   virtual float getFloat(const typename D::ExampleType* ex) const = 0;
                 ^~~~~~~~
prog.cpp:20:7: note: forward declaration of ‘class Derived’
 class Derived : public Base<Derived> {
       ^~~~~~~
prog.cpp:22:11: error: ‘ExampleType’ does not name a type
   typedef ExampleType = Example;
           ^~~~~~~~~~~
prog.cpp:23:17: error: ‘virtual float Derived::getFloatImpl(const Example*)’ marked ‘override’, but does not override
   virtual float getFloatImpl(const Example* ex) override {
                 ^~~~~~~~~~~~
prog.cpp: In instantiation of ‘float Base<D>::getFloat(const FeaturesExample&) const [with D = Derived]’:
prog.cpp:30:30:   required from here
prog.cpp:12:8: error: no type named ‘ExampleType’ in ‘class Derived’
    get(reinterpret_cast<typename D::ExampleType>(&ex));
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
prog.cpp:12:7: error: ‘get’ was not declared in this scope
    get(reinterpret_cast<typename D::ExampleType>(&ex));
    ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Standard output is empty