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some improvements

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Tshepang Mbambo 2026-02-02 23:38:03 +02:00
parent 6169f2e484
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15
src/doc/rustc-dev-guide/src/effects.md
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@ -113,7 +113,9 @@ are revalidated again in [`Checker::revalidate_conditional_constness`].
## `explicit_implied_const_bounds` on associated types and traits
Bounds on associated types, opaque types, and supertraits such as
Bounds on associated types, opaque types, and supertraits such as the following
have their bounds represented differently:
```rust
trait Foo: ~const PartialEq {
type X: ~const PartialEq;
@ -124,9 +126,8 @@ fn foo() -> impl ~const PartialEq {
}
```
Have their bounds represented differently.
Unlike `const_conditions` which need
to be proved for callers, and can be assumed inside the definition (e.g. trait
Unlike `const_conditions`, which need to be proved for callers,
and can be assumed inside the definition (e.g. trait
bounds on functions), these bounds need to be proved at definition (at the impl,
or when returning the opaque) but can be assumed for callers.
The non-const equivalent of these bounds are called [`explicit_item_bounds`].
@ -147,11 +148,11 @@ In general, we can prove a `HostEffect` predicate when either of these condition
* The predicate can be assumed from caller bounds;
* The type has a `const` `impl` for the trait, *and* that const conditions on
the impl holds, *and* that the `explicit_implied_const_bounds` on the trait holds; or
the impl holds, *and* that the `explicit_implied_const_bounds` on the trait holds; or
* The type has a built-in implementation for the trait in const contexts.
For example, `Fn` may be implemented by function items if their const conditions
are satisfied, or `Destruct` is implemented in const contexts if the type can
be dropped at compile time.
are satisfied, or `Destruct` is implemented in const contexts if the type can
be dropped at compile time.
[old solver]: https://doc.rust-lang.org/nightly/nightly-rustc/src/rustc_trait_selection/traits/effects.rs.html
[new trait solver]: https://doc.rust-lang.org/nightly/nightly-rustc/src/rustc_next_trait_solver/solve/effect_goals.rs.html