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Consider if we implement Fn manually (of course this requires nightly)...

Is there a way to work around this issue without imposing additional constraints on map key and value types?

It doesn't appear doable in safe Rust, at least not with reasonable algorithmic complexity. (See Aiden4's answer for a solution that does it by re-building the whole map.)

But if you're allowed to use unsafe, and if you're determined enough that you want to delve into it, this code could do it:

This really appears to have been a compiler bug in the previous version. Up to C# 9.0, structs where not allowed to have a default ctor, and it really was not generated, unlike for classes, where the default ctor was automatically generated when no constructor was defined. This allows to create value types without calling code (by just nullifying the memory). So apparently, they wanted to make this change explicit, because it really makes a difference in the code generated, whether the default constructor exists or not. Do note that in your example, the default constructor is not empty, because any field initializers are implicitly added to the constructor code. So in C# 10, when the constructor is declared, it is generated, otherwise it is left away from the generated IL.

Also note that there are a bunch of pitfalls when using this feature. The default ctor is still not executed when allocating an array of the struct:

Their relationship is like between cargo build and cargo rustc: cargo doc performs all the usual work, for an entire workspace, including dependencies (by default). cargo rustdoc allows you to pass flags directly to rustdoc, and only works for a single crate.

Here is the execution code for cargo rustdoc. Here is the code for cargo doc. The only differences is that cargo rustdoc always specify to not check dependencies while cargo doc allows you to choose (by default it does, but you can specify the flag --no-deps), and that cargo rustc allows you to pass flags directly to rustdoc with the flags after the --.

It happened the same to me last friday. I think it has something to do with Cuda instalation in Google Colab but I don't know exactly the reason

Here is how I think you can model the game in R. The first version is similar to what you have: there's a 50% chance of guessing correctly and if the guess is correct, the players advance a tile. Otherwise they do not, and the number of players decrements by 1. If the number of players reaches 0, or they advance to the end, the game ends. This is shown in squid_bridge1().

Update the Rust to satisfy the new edition 2021.

rustup default nightly && rustup update

Thanks to @ken. Yes, you can use the stable channel too!

But I love nightly personally.

The erase() function may be what you are looking for. It is more flexible than trying to explicitly paint over the areas you want to cover (such as in the approach of using the stroke of a circle and rectangle to cover everything except a circle). And it is easier to use than beginContour() since you can use it with any of the built in drawing primitives (rect, ellipse, triangle, etc).

Old x86-64 CPUs don't support lzcnt, so rustc/llvm won't emit it by default. (They would execute it as bsr but the behavior is not identical.)

Use -C target-feature=+lzcnt to enable it. Try.

More generally, you may wish to use -C target-cpu=XXX to enable all the features of a specific CPU model. Use rustc --print target-cpus for a list.

In particular, -C target-cpu=native will generate code for the CPU that rustc itself is running on, e.g. if you will run the code on the same machine where you are compiling it.