Academics should stick to pure computer science

Every time the academics try to wet their flaccid noodle in the soft, warm crevices of actual programming, they prematurely squirt all over it, and don't get any of their gooey information inside. I'm coming at this from the context of compilers, but I'm sure it applies to most areas. I don't think that anyone could disagree that tomes such as TAoCP are anything less than holy scripture and should be read by anyone who thinks to call them-self a programmer, but beyond that, it's done nothing but waste time. For instance, pure functional programming. Like most academic things, it promises beauty and simplicity and millions of optimizations that can be done. Where are these optimizations? In the math of course. Problem is, most of them never bother to implement them, and on the rare occasion that they do, it's some toy that only shows that particular optimization on a particular instance on a particular program.

The damage comes in when legions of pseudo-intellectuals argue for the style used on the basis that it can merely be shown to allow these optimizations. The rate at which such things actually occur are probably less than one or two percent. Besides looking particularly ``mathy'' in syntax, the result is usually purposeless and never delivers one any of the promises that were theoretically possible.

he doesn't expect the type system to catch logic bugs?

Yeah? That is exactly the kind of shit you expect your type system catches.

as long as it allows me to pass a Set to a function expecting a Bag

That means the type system either is unityped or has subtyping
Now read some Luca Cardelli's introductory papers to type or something, since you clearly don't understand what everyone else is talking about

I also don't see what your point is: I can recreate the exact same problem with Erlang-style classes

My point was according to Alan Kay OO should be more about Erlang-style message passing than about subtyping. I also didn't even mean the problem above doesn't exist in Erlang in case you misunderstood something, it's already a unityped language so talking about ``type'' pitfall is as silly as talking about you're waifu's STDs.