Recent searches
Search options
I can't wait to see how people use default field values in #Rust!
It felt like an eternity to land this (specially if we count the years of discussion before the, I believe, 3rd RFC was accepted), but as of next nightly you will be able to write
struct Foo {
bar: Type = Type::const_method(),
}
Foo { .. } // implicit `bar: Type::const_method()` call
The main difference between https://github.com/rust-lang/rust/pull/129514 and derive(Default) is that the latter doesn't support having mandatory fields.
#RustLang
![Rust Compiler output:
error[E0658]: default values on fields are experimental
--> def.rs:2:11
|
2 | x: i32 = 101,
| ^^^^^^
|
= note: see issue #132162 <https://github.com/rust-lang/rust/issues/132162> for more information
= help: add `#![feature(default_field_values)]` to the crate attributes to enable
= note: this compiler was built on 2024-12-10; consider upgrading it if it is out of date
error[E0797]: base expression required after `..`
--> def.rs:6:19
|
6 | let s = S { .. };
| ^
|
= help: add `#![feature(default_field_values)]` to the crate attributes to enable default values on `struct` fields
help: add a base expression here
|
6 | let s = S { ../* expr */ };
| ++++++++++](https://media.hachyderm.io/media_attachments/files/113/635/417/222/672/459/original/d9ec8030370c26b7.png "Rust Compiler output:
error[E0658]: default values on fields are experimental
--> def.rs:2:11
|
2 | x: i32 = 101,
| ^^^^^^
|
= note: see issue #132162 <https://github.com/rust-lang/rust/issues/132162> for more information
= help: add `#![feature(default_field_values)]` to the crate attributes to enable
= note: this compiler was built on 2024-12-10; consider upgrading it if it is out of date
error[E0797]: base expression required after `..`
--> def.rs:6:19
|
6 | let s = S { .. };
| ^
|
= help: add `#![feature(default_field_values)]` to the crate attributes to enable default values on `struct` fields
help: add a base expression here
|
6 | let s = S { ../* expr */ };
| ++++++++++")
![$ more def.rs
#![feature(default_field_values)]
struct S {
x: i32 = 101,
}
fn main() {
let s = S { .. };
println!("{}", s.x);
}
$ rustc +nightly def.rs && ./def
101](https://media.hachyderm.io/media_attachments/files/113/635/421/842/062/353/original/7bfe5ab368a9ac76.png "$ more def.rs
#![feature(default_field_values)]
struct S {
x: i32 = 101,
}
fn main() {
let s = S { .. };
println!(\"{}\", s.x);
}
$ rustc +nightly def.rs && ./def
101")
@khionu@hachyderm.io@ekuber Really appreciating this, it's basically eliminated all my manual Default implementations