https://github.com/modprog/non-exhaustive

https://github.com/modprog/non-exhaustive

Last synced: about 1 month ago
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• Host: GitHub
• URL: https://github.com/modprog/non-exhaustive
• Owner: ModProg
• License: apache-2.0
• Created: 2024-02-24T14:42:53.000Z (11 months ago)
• Default Branch: main
• Last Pushed: 2024-02-25T23:10:16.000Z (11 months ago)
• Last Synced: 2024-10-28T12:36:01.454Z (3 months ago)
• Language: Rust
• Size: 11.7 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE-APACHE

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README

        
# non-exhaustive

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Macro to create non_exhaustive structs and structs with private fields with the [functional update syntax](https://doc.rust-lang.org/reference/expressions/struct-expr.html#functional-update-syntax), i.e., using `..Default::default()`.

Given the foreign structs:

```rust

#[non_exhaustive]

#[derive(Default)]

pub struct NonExhaustive {

  pub field: usize

}

#[derive(Default)]

pub struct PrivateFields {

  pub pub_field: usize,

  private_field: usize

}

```

The following is not possible:

```rust

NonExhaustive {

  field: 1,

  ..Default::default()

};

PrivateFields {

  pub_field: 1,

  ..Default::default()

};

```

[`non_exhaustive!`] remedies that:

```rust

use non_exhaustive::non_exhaustive;

# mod module {#[derive(Default)] pub struct NonExhaustive {pub field: usize, _hack: usize} #[derive(Default)] pub struct PrivateFields { pub pub_field: usize, private_field: usize}} use module::*;

non_exhaustive! {NonExhaustive {

  field: 1,

  ..Default::default()

}};

non_exhaustive! {PrivateFields {

  pub_field: 1,

  ..Default::default()

}};

```

For the common case of using [`Default::default()`], [`non_exhaustive!`] allows omitting the `..expression`:

```rust

use non_exhaustive::non_exhaustive;

# mod module {#[derive(Default)] pub struct NonExhaustive {pub field: usize, _hack: usize} #[derive(Default)] pub struct PrivateFields { pub pub_field: usize, private_field: usize}} use module::*;

non_exhaustive!(NonExhaustive { field: 1 });

non_exhaustive!(PrivateFields { pub_field: 1 });

```

Under the hood, [`non_exhaustive!`] is extremely simple, it expands to:

```rust

# mod module {#[derive(Default)] pub struct NonExhaustive {pub field: usize, _hack: usize}} use module::*;

{

  let mut value: NonExhaustive = Default::default();

  value.field = 1;

  value

};

```

[`non_exhaustive!`]: https://docs.rs/non-exhaustive/latest/non_exhaustive/macro.non_exhaustive.html

[`Default::default()`]: https://doc.rust-lang.org/std/default/trait.Default.html