Lib.rs

This project is no longer maintained.

lib.rs:

"Infer" the lengths of arrays in array static/const items.

Crate feature

• no-core: Make this crate #![no_core].

  #![no_core] example

  #![feature(no_core, lang_items, start)] #![no_core]

  #[cfg_attr(not(windows), link(name = "c"))] #[cfg_attr(windows, link(name = "msvcrt"))] extern "C" {}

  use infer_len::infer_len;

  #[lang = "sized"] trait Sized {}

  #[lang = "eh_personality"] fn eh_personality() -> ! { loop {} }

  #[lang = "receiver"] trait Receiver {}

  impl<T: ?Sized> Receiver for &T {}

  #[lang = "copy"] trait Copy {}

  impl Copy for i32 {}

  #[lang = "array"] impl [i32; 5] { const fn len(self) -> usize { 5 } }

  infer_len! { const FOO: [i32; _] = [1, 2, 3, 4, 5]; pub(crate) const BAR: &[i32; _] = &FOO; pub(self) const BAZ: [i32; _] = [6, 7, 8, 9, 10]; }

  #[start] fn main(_: isize, _: *const *const u8) -> isize { let _: [i32; 5] = FOO; let _: &[i32; 5] = BAR; let _: [i32; 5] = BAZ; 0 }

  </details>
  
  

Example

mod foo {
    # use infer_len::infer_len;
    use std::convert;

    infer_len! {
        pub(self) const FOO: &[i128; _] = &[-1, -2, -3, -4];
        const BAR: [i128; _] = *FOO;
        pub static BAZ: [i128; _] = BAR;
        pub(super) static HELLO_WORLD: &[u8; _] = b"Hello World";
        #[allow(non_upper_case_globals)] // attribute works
        static qux: [i128; _] = convert::identity(BAR); // arbitrary expression works
        #[allow(non_upper_case_globals)]
        #[used] // multiple attributes works
        static used: [i128; _] = convert::identity(*FOO);
        pub(crate) const QUZ: &[i128; _] = FOO;
    }

    fn _foo() {
        let _: &[i128; 4] = FOO;
        let _: [i128; 4] = BAR;
        let _: [i128; 4] = qux;
    }
}

let _: &[u8; 11] = foo::HELLO_WORLD;
let _: [i128; 4] = foo::BAZ;
let _: &[i128; 4] = foo::QUZ;