I would say the sharp edges aren't unexpected runtime behavior — compiles => works as expected, barring off by one errors — but rather things like “I just spent an hour figuring out the best way to build a tree out of nested HashMaps because the borrow checker didn't want me to do overlapping mutable borrows” or “what's the right way to be agnostic with regard to owned or borrowed data in my struct/function”. I don't consider these to be part of the learning curve because the problems are inherently more complicated than just “how do I use rust”.
Conventionally we use "sharp edges" to mean things which are dangerous in a surprising way. For example freshly cut paper has a sharp edge, it's very easy to cut yourself painfully on a sheet of blank paper. The things you've described don't threaten to be dangerous or surprising. They're not good but they don't strike me as "sharp edges".
I see what you mean. As the sibling noted, I think you're using "sharp edges" in an unconventional way, but Rust definitely has a sort of unpredictable developer experience. Some things go really fast and the programmer finds themselves thinking, "wow! this is as easy as Python/Go/whatever!" and other times something that seems to be easy fails to compile and you get a compiler error that says you need to fix one seemingly small thing, so you try and fix that small thing and you get another seemingly-easy-to-fix compiler error and you just keep pulling on that thread until you've forgotten the problem you were originally setting out to solve. (:
I don't think this is a "sharp edge" (maybe "indeterminately long threads to pull") but it definitely is an unpleasant experience. If anyone knows of any good names for this category of frustration, I'd be happy to hear them!
