How designing Carbon with C++ interop taught me about C++ variadics and overloads

C++ has some amazing and powerful language features, but they can be difficult to understand. Moving past a basic understanding of a feature and common patterns of use requires a deep understanding of the underlying language design so that you can model how it works and how to effectively use it. But how do you develop a rich and compelling model for these parts of C++?

The Carbon language aims for seamless and comprehensive interop with C++, including these complex and powerful aspects of the language. As a consequence, in order to design Carbon's features, we have to build exactly that rich and compelling model for C++ features they interoperate with. A surprising but delightful outcome is that the Carbon designs can often be used to build an even deeper and more effective understanding of C++ itself.

This talk will work through the design of two Carbon features with significant C++ overlap: variadics and overloaded methods. We will build up a design model for them, and show how you can use that model to think more deeply and holistically about the design of C++ code. It will also show how to build more expressive or robust C++ APIs through that model, even where C++ doesn't give you perfect building blocks. And most of all, it will showcase a fun and interesting way to learn about language design, and reason more deeply about the underlying principles of your code.