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Auto merge of #94901 - fee1-dead:destructable, r=oli-obk

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Rename `~const Drop` to `~const Destruct`

r? `@oli-obk`

Completely switching to `~const Destructible` would be rather complicated, so it seems best to add it for now and wait for it to be backported to beta in the next release.

The rationale is to prevent complications such as #92149 and #94803 by introducing an entirely new trait. And `~const Destructible` reads a bit better than `~const Drop`. Name Bikesheddable.
This commit is contained in:
bors 2022-03-23 14:04:38 +00:00
commit 9280445570
32 changed files with 308 additions and 187 deletions
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16
compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs
View file

@ -3,6 +3,7 @@
//! See the `Qualif` trait for more info.
use rustc_errors::ErrorGuaranteed;
use rustc_hir::LangItem;
use rustc_infer::infer::TyCtxtInferExt;
use rustc_infer::traits::TraitEngine;
use rustc_middle::mir::*;
@ -152,18 +153,14 @@ impl Qualif for NeedsNonConstDrop {
return false;
}
let Some(drop_trait) = cx.tcx.lang_items().drop_trait() else {
// there is no way to define a type that needs non-const drop
// without having the lang item present.
return false;
};
let destruct = cx.tcx.require_lang_item(LangItem::Destruct, None);
let obligation = Obligation::new(
ObligationCause::dummy(),
cx.param_env,
ty::Binder::dummy(ty::TraitPredicate {
trait_ref: ty::TraitRef {
def_id: drop_trait,
def_id: destruct,
substs: cx.tcx.mk_substs_trait(ty, &[]),
},
constness: ty::BoundConstness::ConstIfConst,
@ -174,15 +171,16 @@ impl Qualif for NeedsNonConstDrop {
cx.tcx.infer_ctxt().enter(|infcx| {
let mut selcx = SelectionContext::new(&infcx);
let Some(impl_src) = selcx.select(&obligation).ok().flatten() else {
// If we couldn't select a const drop candidate, then it's bad
// If we couldn't select a const destruct candidate, then it's bad
return true;
};
if !matches!(
impl_src,
ImplSource::ConstDrop(_) | ImplSource::Param(_, ty::BoundConstness::ConstIfConst)
ImplSource::ConstDestruct(_)
| ImplSource::Param(_, ty::BoundConstness::ConstIfConst)
) {
// If our const drop candidate is not ConstDrop or implied by the param env,
// If our const destruct candidate is not ConstDestruct or implied by the param env,
// then it's bad
return true;
}