I wonder if there's just some cultural / generational stuff happening there too. The fact that the TS compiler is all about compiling a highly complex OOP/functional hybrid language yet is said to use neither objects nor FP seems rather telling. Hejlsberg is famous for designing object oriented languages (Delphi, C#) but the Delphi compiler itself was written largely in assembly, and the C# compiler was for a very long time written in C++ iirc. It's possible that he just doesn't personally like working in the sort of languages he gets paid to design.
There's an interesting contrast here with Java, where javac was ported to Java from C++ very early on in its lifecycle. And the Java AOT compiler (native image) is not only fully written in Java itself, everything from optimizations to code generation, but even the embedded runtime is written in Java too. Whereas in the .NET world Roslyn took quite a long time to come along, it wasn't until .NET 6, and of course MS rejected it from Windows more or less entirely for the same sorts of rationales as what Anders provides here.
It was introduced back then with .NET Framework 4.6 (C# 6) - a loong time ago (July 2015). The OSS .NET has started with Roslyn from the very beginning.
> And the Java AOT compiler (native image) is not only fully written in Java itself, everything from optimizations to code generation, but even the embedded runtime is written in Java too.
NativeAOT uses the same architecture. There is no C++ besides GC and pre-existing compiler back-end (both ILC and RyuJIT drive it during compilation process). Much like GraalVM's Native Image, the VM/host, type system facilities, virtual/interface dispatch and everything else it could possibly need is implemented in C# including the linker (reachability analysis/trimming, kind of like jlink) and optimizations (exact devirtualization, cctor interpreter, etc.).
In the end, it is the TypeScript team members who worked on this port, not Anders Hejlsberg himself, which is my understanding. So we need to take this into account when judging what is being communicated.
There's an interesting contrast here with Java, where javac was ported to Java from C++ very early on in its lifecycle. And the Java AOT compiler (native image) is not only fully written in Java itself, everything from optimizations to code generation, but even the embedded runtime is written in Java too. Whereas in the .NET world Roslyn took quite a long time to come along, it wasn't until .NET 6, and of course MS rejected it from Windows more or less entirely for the same sorts of rationales as what Anders provides here.