> I feel obsessing over types is often just a form of procrastination
Can confirm, this happened to me in Java constantly. I once spent an hour writing a big utility class using generics, even though I needed it for only one type in the code. "What if I need it for something else? Copying the code and replacing the types is very inefficient!"
Turned out that Java, being Java, was unable to instantiate an empty array of a generic type, so the very elegant code in the utility class now meant having to handle a bunch of special null cases in the application. I actually left it in for a while, but thankfully changed my mind before merging it as I'm sure the team wouldn't have appreciated having to deal with even more null in unexpected places because I got attached to my shiny generic code.
That sounds like a problem with Java more than a problem with generics.
In general, I agree with your sentiment. Though in some cases, an abstraction can be justified even when used only once.
Take the simple case of a function. Generally a function only communication with its surroundings via parameters and returned values. A function that respects those conventions makes reading code much easier, and can be worth it even if used only once.
In contrast, a code block inside a much larger stretch of code doesn't give the reader any explicit guidance one how it intends to interact with the rest of the system. Even if it's exactly the same code as in the function.
Similarly, a for-loop can do almost anything. But using map or filter immediately tells you that only a few things are possible here. Even a fold is more restricted than a general for-loop.
Can confirm, this happened to me in Java constantly. I once spent an hour writing a big utility class using generics, even though I needed it for only one type in the code. "What if I need it for something else? Copying the code and replacing the types is very inefficient!"
Turned out that Java, being Java, was unable to instantiate an empty array of a generic type, so the very elegant code in the utility class now meant having to handle a bunch of special null cases in the application. I actually left it in for a while, but thankfully changed my mind before merging it as I'm sure the team wouldn't have appreciated having to deal with even more null in unexpected places because I got attached to my shiny generic code.