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Auto merge of #135186 - camelid:const-path-multi, r=BoxyUwU

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mgca: Lower all const paths as `ConstArgKind::Path`

When `#![feature(min_generic_const_args)]` is enabled, we now lower all
const paths in generic arg position to `hir::ConstArgKind::Path`. We
then lower assoc const paths to `ty::ConstKind::Unevaluated` since we
can no longer use the anon const expression lowering machinery. In the
process of implementing this, I factored out `hir_ty_lowering` code that
is now shared between lowering assoc types and assoc consts.

This PR also introduces a `#[type_const]` attribute for trait assoc
consts that are allowed as const args. However, we still need to
implement code to check that assoc const definitions satisfy
`#[type_const]` if present (basically is it a const path or a
monomorphic anon const).

r? `@BoxyUwU`
This commit is contained in:
bors 2025-03-04 22:37:37 +00:00
commit 08db600e8e
35 changed files with 602 additions and 148 deletions
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20
compiler/rustc_middle/src/ty/assoc.rs
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@ -3,7 +3,7 @@ use rustc_hir as hir;
use rustc_hir::def::{DefKind, Namespace};
use rustc_hir::def_id::DefId;
use rustc_macros::{Decodable, Encodable, HashStable};
use rustc_span::{Ident, Symbol};
use rustc_span::{Ident, Symbol, sym};
use super::{TyCtxt, Visibility};
use crate::ty;
@ -108,6 +108,24 @@ impl AssocItem {
pub fn is_impl_trait_in_trait(&self) -> bool {
self.opt_rpitit_info.is_some()
}
/// Returns true if:
/// - This trait associated item has the `#[type_const]` attribute,
/// - If it is in a trait impl, the item from the original trait has this attribute, or
/// - It is an inherent assoc const.
pub fn is_type_const_capable(&self, tcx: TyCtxt<'_>) -> bool {
if self.kind != ty::AssocKind::Const {
return false;
}
let def_id = match (self.container, self.trait_item_def_id) {
(AssocItemContainer::Trait, _) => self.def_id,
(AssocItemContainer::Impl, Some(trait_item_did)) => trait_item_did,
// Inherent impl but this attr is only applied to trait assoc items.
(AssocItemContainer::Impl, None) => return true,
};
tcx.has_attr(def_id, sym::type_const)
}
}
#[derive(Copy, Clone, PartialEq, Debug, HashStable, Eq, Hash, Encodable, Decodable)]