[gfna]

c# has been my go to language for everything except frontends for the past 15 years, but there are still some things I really miss from Rust. The top one is probably pattern matching. Sure C# has something similar with switch expressions, but with them you must assign something, and they cannot contain code blocks. Related to this something like enum variants is also missing, and therefore making something similar to Result or Option is not really feasible without it being quite hacky. Also being able to create new types from existing ones with eg struct Years(i64); and pass it around typed is quite nice in Rust (F# has something similar, however there it will then always also be assignable to i64, so is not very helpful for catching incorrect usage.

[arwhatever]

I’d be eager to hear folks poke holes in this opinion, but it seems like C# has made a wild mess of class/record initialization in recent versions, whereas in Rust fields are either simply required or are optional.

[neonsunset]

Properties in C# follow a similar pattern. Constructors can have their own arguments which can also be mandatory or optional. In Rust this logic simply lives in a function instead.

The only issue in C# is that structs come with a. default parameterless constructor (which can be overridden) and b. can be default-intialized (default(T)) without the compiler complaining by default. These two aspects are not ideal and cannot be walked back as they were introduced in ancient times but are rarely an issue in practice (and you can further use an analyzer to disallow either).

F# is more strict about it however and does not have such gaps.

[arwhatever]

There’s also (in C#) init, readonly, required, and quite a few more keywords and techniques, governing property mutability, private class field mutability, and so on.

And then none of those techniques work as well as manually typing out a required constructor which hard-enforces that required data be priced upon object initialization.

I understand required vs optional immediately a la Rust and F# (ignoring for a moment F#’s null awareness) but as a 17 year C# dev, I’ve had to create an initialization chart to keep straight all of the C# techniques.

[neonsunset]

> Also being able to create new types from existing ones with eg struct Years(i64); and pass it around typed is quite nice in Rust (F# has something similar, however there it will then always also be assignable to i64, so is not very helpful for catching incorrect usage.

F# has units of measure which are quite a bit more powerful: https://learn.microsoft.com/en-us/dotnet/fsharp/language-ref...