i reread this tutorial about rust subtype and variance: Subtyping and Variance - The Rustonomicon . it says UnsafeCell<T> is invariant over T. but i remember that the struct definition of UnsafeCell is following pub struct UnsafeCell<T: ?Sized> { value: T, } this conclusion is counter intuitiv…

[image] hex42: but also a part of the rust language itself Exactly. And that's the point. The definition of UnsafeCell is #[lang = "unsafe_cell"] #[stable(feature = "rust1", since = "1.0.0")] #[repr(transparent)] pub struct UnsafeCell<T: ?Sized> { value: T, } Note #[lang] macro means th…

Note #[lang] is now included on some none special types and functions. [image] Why are Option variants lang items? I wanted to make a point to someone who I'm introducing to Rust that "Option isn't special, just a regular type provided by the std library", but when I chec…

Thanks for the link and the great discussions there. I haven't seen it before, but had the same question in mind. Maybe there should be an official documentation that describes the current lang items. Glad to see them in the specifications (like Ferrocene Language Specification — Ferrocene Language …

Is UnsafeCell a language feature just like PhantomData?

help

jonh August 17, 2023, 3:06pm 3

Note #[lang] is now included on some none special types and functions.

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Is UnsafeCell a language feature just like PhantomData?

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