> Can you show me an example of Rust promising "if it compiles it works"? [...] and I've never heard anybody working on or in Rust claim that this is something you can just provide with absolute confidence.

I have heard it and I've stated it before. It's never stated in absolute confidence. As I said in another thread, if it was actually true, then Rust wouldn't need an integrated unit testing framework.

It's referring to the experience that Rust learners have, especially when writing relatively simple code, that's it tends to be hard to misuse libraries in a way that looks correct and compiles but actually fails at runtime. Rust cannot actually provide this guarantee, it's impossible in any language. However there are a lot of common simple tasks (where there's not much complex internal logic that could be subtly incorrect) where the interfaces provided by libraries they're depending on are designed to leverage the type system such that it's difficult to accidentally misuse them.

Like something like not initializing a HTTP client properly. The interfaces make it impossible to obtain an improperly initialized client instance. This is an especially distinct feeling if you're used to dynamic languages where you often have no assurances at all that you didn't typo a field name.