A comparison of Rust's borrow checker to the one in C#

Re:A comparison of Rust's borrow checker to the one in C# by alkonaut on Thursday October 31, 2024 @09:00AM (#42006479)

The DU stuff is enormous once you consider all the corners it touches. Especially with refinements. E.g. in code like

if (s is string or s is int) { // what's the type of s here? is it "string | int" ? }

And not to mention that the BCL should probably get new overloads using DU's for some APIs. But there is at least a work in progress now, after years of nothing.

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Re:A comparison of Rust's borrow checker to the one in C# by colejohnson66 on Thursday October 31, 2024 @11:34AM (#42007927)

One of the claimed benefits of .NET Core was that they could improve the runtime at a much faster pace than .NET Framework did, especially if that meant adding new features or even IL opcodes. And they've done this before, with a big one (IMO) being ref fields in ref structs. Lately, when it comes to developing C#, the language design team has frustratingly been trying to shoehorn everything into the compiler instead of modifying the runtime. Then they say the runtime should be modified to pattern-match what they output. If DUs are to be implemented fully in C#, niches would probably be impossible. This means Optional<T>, when T is a class, would take two words.

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