Rust 1.38 has been released, and the contents of the stable version 1.38.0 are as follows:
Pipelined Compilation
If you want to compile a crate, the compiler does not need to fully build dependencies; it only requires their “metadata” (i.e., types, dependencies, exported lists), which is generated early in the compilation process. Starting from Rust 1.38.0, Cargo will leverage this advantage and automatically begin building dependent crates as soon as the metadata is ready.
Although this change does not affect the compilation of individual crates, tests have reported that for builds involving multiple crates, it can bring about a 10-20% increase in compilation speed for clean and optimized builds. Other improvements are minimal, and the speed increase depends on the hardware running the build.
mem::{uninitialized, zeroed}
Starting from 1.38, rustc will provide lints for narrow types that are incorrectly initialized using mem::uninitialized or mem::zeroed.
#[deprecated] Macros
The #[deprecated] attribute was originally introduced in Rust 1.9.0. Rust 1.38.0 extends this attribute to allow it to be applied to macros, marking macros as deprecated using the deprecated attribute.
std::any::type_name
For debugging, obtaining the name of a type can sometimes be useful. For example, in generic code, you might want to see the specific type that a function’s type parameter is instantiated to at runtime. This version allows you to achieve this using std::any::type_name:
fn gen_value<T: Default>() -> T {
println!("Initializing an instance of {}", std::any::type_name::<T>());
Default::default()
}
fn main() {
let _: i32 = gen_value();
let _: String = gen_value();
}
Output:
Initializing an instance of i32
Initializing an instance of alloc::string::String
Library Changes
-
slice::{concat, connect, join} now supports &[T] and &T
-
*const T and *mut T now implement maker::Unpin
-
Arc<[T]> and Rc<[T]> implement FormIterator<T>
-
iter::StepBy, Peekable, Take implement DoubleEndedIterator
Additionally, the following features have been stabilized:
-
<span>Duration::div_duration_f32</span>and<span>Duration::div_duration_f64</span> -
<span><*const T>::cast</span>and<span><*mut T>::cast</span> -
<span>Duration::as_secs_f32</span>and<span>Duration::as_secs_f64</span> -
<span>Duration::div_f32</span>and<span>Duration::div_f64</span> -
<span>Duration::from_secs_f32</span>and<span>Duration::from_secs_f64</span> -
<span>Duration::mul_f32</span>and<span>Duration::mul_f64</span>
To obtain version 1.38, use the following command:
rustup update stable
For more details, please check the original article.
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