Announcing Rust 1.76.0

A new ABI Compatibility section in the function pointer documentation describes what it means for function signatures to be ABI-compatible. A large part of that is the compatibility of argument types and return types, with a list of those that are currently considered compatible in Rust. For the most part, this documentation is not adding any new guarantees, only describing the existing state of compatibility.

The one new addition is that it is now guaranteed that char and u32 are ABI compatible. They have always had the same size and alignment, but now they are considered equivalent even in function call ABI, consistent with the documentation above.

For debugging purposes, any::type_name::<T>() has been available since Rust 1.38 to return a string description of the type T, but that requires an explicit type parameter. It is not always easy to specify that type, especially for unnameable types like closures or for opaque return types. The new any::type_name_of_val(&T) offers a way to get a descriptive name from any reference to a type.

fn get_iter() -> impl Iterator<Item = i32> {
    [1, 2, 3].into_iter()
}

fn main() {
    let iter = get_iter();
    let iter_name = std::any::type_name_of_val(&iter);
    let sum: i32 = iter.sum();
    println!("The sum of the `{iter_name}` is {sum}.");
}

This currently prints:

The sum of the `core::array::iter::IntoIter<i32, 3>` is 6.