I really prefer the flat variant cause it helps me ensure exhaustiveness. In the end people probably trained their brain to read the nested variant to the point it's transparent to their neurons.

I think the lines gets blurred when doing early exits and guard conditions.

For instance

  if !condition_a && !conditon_b {
    return fn_d() // probably an error condition ?
  }

  if condition_a && condition_b {
    return fn_a()
  }

  if condition_a {
   fn_b()
  } else {
   fn_c()
  }

These 3 examples optimize to the the same thing because they generate identical instructions:

https://godbolt.org/z/a1Yq9rceE

Note: Inverting and rearranging conditions changes what LLVM decides to output, sometimes for the worse. --opt-level=s is counterproductive here.

Oh no, hard disagree. The match implementation is far easier to reason about. I can see at a glance that if both condition_a and condition_b are true, call fn_a(). For the nested if version I have to trace each expression by hand.

They said "isn't", not "is". Double negative. You two agree.

Ugh. I missed that. No wonder my grade school teachers taught us "don't use no double negatives".

I think I would like the former syntax. Witness one of the several nested matching situations I run into:

https://github.com/titzer/wizard-engine/blob/master/src/engi...

This would be much, much better if Virgil had pattern matching on tuples of ADTs.