This slogan sucks. If it compiles, it type checks. Yes, Rust has a more sophisticated type system than Python with annotations, so it catches more type errors.
No, the type system cannot prevent logic bugs or design bugs. Stop pretending it does.
Obviously a type system cannot catch all your logic errors, but you can write code such that more of the logic is encapsulated in types, which _does_ help to catch a lot of logic errors.
There's a strong qualitative difference working with the Rust compiler versus working with Python or C++. Do you have a better suggestion for how to express that?
Also, no, the Rust compiler will happily pass code which will crash your program, all it takes is an out of bounds array access. That's the kind of puffery many of us are tired of. The "if it compiles, it works" slogan is, bluntly, wrong.
The only two languages I’ve worked with that gave me the feeling that I could generally trust a compiling program to be approximately correct are Rust and Haskell. That difference relative to other languages is meaningful enough in practice that it seems to me to be worth a slogan. I believe it’s meant to be more of a “works, relative to what you might expect from other languages” kind of thing versus, “is a completely perfect program.”
And, if you care about maximizing the “if it compiles it works” feeling, it’s possible to use .get() for array access, to put as much logic in the type system as is feasible, etc. This is probably more idiomatic and is generally how I write code, so it does often feel that way to me, regardless of whether it is completely, objectively, literally true.
It's not tautological at all, because the type system in Rust and Haskell is not a trivial condition of the language.
> not particularly effective as a saying or slogan
Neither is "if it compiles it runs", rather less so in fact, everyone is sick of hearing it, and rolls their eyes so hard it's actually audible.
Every one of these 764 bugs compiled and passed type checks:
https://github.com/tokio-rs/tokio/labels/C-bug
Not picking on tokio in particular, mind you, finding and fixing bugs is a sign of quality in a library or program.
> I believe it’s meant to be more of a “works, relative to what you might expect from other languages” kind of thing versus, “is a completely perfect program.”
Which is why I describe it as meaningless puffery. What you're saying here is that you know full well it isn't true, but want to keep saying it anyway. My reply is find a way to express yourself which is true, rather than false. I bet you can figure one out.
^ your words, that statement is false. the type system _can_ prevent logic bugs or design bugs, exhaustive pattern matching is an obvious example.
I bet you can find a way to express yourself which is true, e.g. "the type system cannot prevent _all_ logic bugs or design bugs"