const generics update

This commit is contained in:
lcnr 2021-09-20 19:10:40 +02:00 committed by Joshua Nelson
parent ee746de3af
commit 7a476c07e1
2 changed files with 5 additions and 4 deletions

View File

@ -98,6 +98,7 @@
- [Generics and substitutions](./generics.md)
- [`TypeFolder` and `TypeFoldable`](./ty-fold.md)
- [Generic arguments](./generic_arguments.md)
- [Constants in the type system](./constants.md)
- [Type inference](./type-inference.md)
- [Trait solving](./traits/resolution.md)
- [Early and Late Bound Parameters](./early-late-bound.md)

View File

@ -7,20 +7,20 @@ with the two *additional* variants being `ConstKind::Value` and `ConstKind::Unev
## Unevaluated constants
*This section talks about what's happening with `feature(const_generics)` enabled.
*This section talks about what's happening with `feature(generic_const_exprs)` enabled.
On stable we do not yet supply any generic parameters to anonymous constants,
avoiding most of the issues mentioned here.*
Unless a constant is either a simple literal, e.g. `[u8; 3]` or `foo::<{ 'c' }>()`,
or a generic parameter, e.g. `[u8; N]`, converting a constant to its [`ty::Const`] representation
returns an unevaluated constant. Even fully concrete constants which do not depend on a
generic parameter are not evaluated right away.
returns an unevaluated constant. Even fully concrete constants which do not depend on
generic parameters are not evaluated right away.
We do not eagerly evaluate constant as they can be used in the `where`-clauses of their
parent item, for example:
```rust
#[feature(const_generics, const_evaluatable_checked)]
#[feature(generic_const_exprs)]
fn foo<T: Trait>()
where
[u8; <T as Trait>::ASSOC + 1]: SomeOtherTrait,