Any self-hosting language compiler has to start from somewhere. Generally it's an incremental process where the compiler for an early/subset version of the lan

Any self-hosting language compiler has to start from somewhere. Generally it's an incremental process where the compiler for an early/subset version of the language is written in another, existing language (absent one, may be assembly code). Once it's possible to rewrite the compiler in its own subset language, it becomes self-hosting. Then you can add a feature to the language, and once it works, enhance the compiler to use it, and so on. Eventually the language and compiler go hand-in hand: The only way to compile it is with a compiler, and the only way to compile the compiler is with itself. This leads to interesting thought experiments such as: https://www.cs.cmu.edu/~rdriley/487/papers/Thompson_1984_ReflectionsonTrustingTrust.pdf https://www.cs.cmu.edu/~rdriley/487/papers/Thompson_1984_Ref...