+1 to implementing a Rust interpreter. You can skip the entire middle and backend of the compiler, and if the program doesn't do much, this will be faster than

+1 to implementing a Rust interpreter. You can skip the entire middle and backend of the compiler, and if the program doesn't do much, this will be faster than any other solution. The Virgil compiler includes an interpreter for the entire language (by necessity--initialization of components can use the full language). This can be exploited to run all of your unit tests in interpreted mode, skipping the compilation step. This is a huge win. It's a win to the point that developing the compiler itself, I often run the compiler in the stable compiler's interpreter (~85ms), to skip the entire bootstrapping step (~400ms).