Parse, don't validate (2019)

Note that this basically requires your language to have ergonomic support for sum types, immutable "data classes", pattern matching.

The point is to parse the input into a structure which always upholds the predicates you care about so you don't end up continuously defensively programming in ifs and asserts.

I think we'll eventually come to regard `if` as we do `goto`.

I don't know about this. We all have seen this kind of code:

    if(!needToDoTheThing()) return;
    
    DoTheThing();

We could have written it this way:

    if(needToDoTheThing()) {
        DoTheThing();
    }
    else {
        return;
    }

The later is closer to how pattern match looks like. But in my experience, the majority of programmers prefer early return. I regularly see people "refactor" if-else to if-early-return, but I've never seen the opposite.