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|
use super::*;
pub fn emit_impls() -> ::std::io::Result<()> {
let out_dir = ::std::env::var("OUT_DIR").unwrap();
let dest = ::std::path::Path::new(&out_dir).join("generic_const_mappings.rs");
println!(
"cargo:rustc-env=TYPENUM_BUILD_GENERIC_CONSTS={}",
dest.display()
);
let mut f = ::std::fs::File::create(&dest).unwrap();
#[allow(clippy::write_literal)]
write!(f, "{}", "\
#[cfg(doc)]
use generic_const_mappings::*;
/// Module with some `const`-generics-friendly definitions, to help bridge the gap
/// between those and `typenum` types.
///
/// - It requires the `const-generics` crate feature to be enabled.
///
/// The main type to use here is [`U`], although [`Const`] and [`ToUInt`] may be needed
/// in a generic context.
#[allow(warnings)] // script-generated code
pub mod generic_const_mappings {
use crate::*;
/// The main mapping from a generic `const: usize` to a [`UInt`]: [`U<N>`] is expected to work like [`UN`].
///
/// - It requires the `const-generics` crate feature to be enabled.
///
/// [`U<N>`]: `U`
/// [`UN`]: `U42`
///
/// # Example
///
/// ```rust
/// use typenum::*;
///
/// assert_type_eq!(U<42>, U42);
/// ```
///
/// This can even be used in a generic `const N: usize` context, provided the
/// genericity is guarded by a `where` clause:
///
/// ```rust
/// use typenum::*;
///
/// struct MyStruct<const N: usize>;
///
/// trait MyTrait { type AssocType; }
///
/// impl<const N: usize> MyTrait
/// for MyStruct<N>
/// where
/// Const<N> : ToUInt,
/// {
/// type AssocType = U<N>;
/// }
///
/// assert_type_eq!(<MyStruct<42> as MyTrait>::AssocType, U42);
/// ```
pub type U<const N: usize> = <Const<N> as ToUInt>::Output;
/// Used to allow the usage of [`U`] in a generic context.
pub struct Const<const N: usize>;
/// Used to allow the usage of [`U`] in a generic context.
pub trait ToUInt {
/// The [`UN`][`crate::U42`] type corresponding to `Self = Const<N>`.
type Output;
}
\
")?;
for uint in uints() {
write!(
f,
"
impl ToUInt for Const<{uint}> {{
type Output = U{uint};
}}
\
",
uint = uint,
)?;
}
write!(f, "}}")?;
f.flush()?;
Ok(())
}
|
