It doesn’t need to be / it is, depending on perspective. The C# compiler, for example, has what’s called a “semantic speculative model” wherein it will use vari

It doesn’t need to be / it is, depending on perspective. The C# compiler, for example, has what’s called a “semantic speculative model” wherein it will use various heuristics to know when you need to re-typecheck things or not (e.g., editing just the body of a method without changing a type signature kicks off much less work than if you also change the return type). But it’s also just really fucking fast and will use as many threads as you want it to, so it can also be kinda moot too. Very rarely is the compiler actually a bottleneck in the C# case, but could be in others.