TypeScript is a perfect example. It can compile with typechecking, or, due to the design of the language, without any consideration of types at all. This late

TypeScript is a perfect example. It can compile with typechecking, or, due to the design of the language, without any consideration of types at all. This later mode is extremely fast, particularly with per file incrementality. (Unfortunately for reasons I cannot fathom, this is not part of tsc CLI. You have to use something like Babel that uses the TS compiler API.)