The just-in-time compiler (JIT) is a mighty beast of the .NET runtime. And it becomes more powerful with every release of .NET. But it comes along with a cost during run-time, when compiling the assemblies containing intermediate language code into machine code. A price we may not pay gladly for highly scalable cloud services. Native AOT, compiling deployments ahead-of-time into executable code, moves this complexity to compile-time. But features that utilize dynamic code emission may stop working.

C# 12.0 - shipped with .NET 8.0 - brings us a new experimental language feature: Interceptors. An interceptor is basically the inverse of a goto statement that enables the Roslyn compiler to replace reflection-based call sites with specialized implementations. Combined with (incremental) source generators, codebases become more trimmable, more Native AOT-friendly and can unlock better performance.

Let's inspect this new concept in detail and see it in action.