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Comment by fauigerzigerk | Hacker News Reader

I'm fine with either approach if it's easy to know which one I'm using at a any particular call site. C# started the tradition of moving this information to the type level, far away from the call site. Swift has adopted this terrible idea.

The philosophy of making code look "clean" at the cost of hiding critical information in some far away place is the biggest mistake in programming language design. If code happens to look clean it should be the result of being simple rather than being cleansed for effect.

Other bad ideas in the same vein are computed properties and function builders.

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Computed properties are annoying too. More importantly, they're one more inconsequential thing for SWEs to argue over in code review.

What do you mean by moving information to the type level?

In C and C++ (and many other languages) the distinction between value and reference/pointer is part of the variable declaration. In C# and Swift that information belongs to type definitions (except for inout parameters). Structs are value types and classes are reference types.

Type definitions are usually further away from the call site than variable declarations. Also, in C, accessing a member of a struct through a pointer requires the -> operator providing yet another clue as to whether you're using a pointer or a value.

In my opinion, this distinction is absolutely key. It should always be obvious at the call site. I don't think there is anything that has caused more bugs in my Swift code than getting this wrong.

Change a type from class to struct or vice versa and chances are your code still compiles when it really shouldn't because it's now completely broken.

If there are identity having classes (reference/pointer) that may be mutable, and value types that are always immutable, then I think it can be an “implementation detail”, part of the type, not changing semantics.

If you can’t change a struct’s field, only the whole struct, then I believe it’s fine - and the compiler may decide to copy it or change in-place depending on its available context, is it not the case?

In a language without mutability (or perhaps with something like borrow checking?), it would not be a problem. But in Swift, the option of introducing mutability always exists.

It's not impossible to impose some sort of discipline to mitigate these issues, but why is it a good idea to make values and references indistinguishable at the call site? I don't get it.

But it's not surprising. I don't get a lot of decisions that language designers have been making. The entire drive towards more and more syntactical abstraction in order to make everything look like a DSL is a mistake in my opinion.

Refs in C++ go against this, right? At the call site, it's not clear that you're passing in a ref instead of a value. I don't mind it too much cause at least the rules are the same for everything, not different for structs vs classes.

Yes. At least references are still part of the variable type and therefore likely to be closer to the call site.

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