Nikolai Panov

https://github.com/isocpp/CppCoreGuidelines/blob/6f27719b2b994d1304f78194dc7824e4ddeea5f5/CppCoreGuidelines.md?plain=1#L18251 The argument of `copy_trait` must be a container element type instead of `Iter`. Probably there should be `copy_trait` like in the next sample. https://github.com/isocpp/CppCoreGuidelines/blob/6f27719b2b994d1304f78194dc7824e4ddeea5f5/CppCoreGuidelines.md?plain=1#L18266-L18267 And another typo is in...

T.21 Fix wrong return type

1

The code was likely copied from the example above, but the return type was not replaced.

Method `do_something_impl` is `private` in the base class and `public` in the derived class `foo`. https://github.com/sftrabbit/CppPatterns-Patterns/blob/a222c8438d2c9e81114b9408c2e6a8e767bffb0b/common-tasks/classes/delegate-behavior-to-derived-classes.cpp#L21-L28 For consistency, make `do_something_impl` private. ```c++ class foo : public base { friend class...

Add private access specifier to the `foo` class.