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Auto merge of #118133 - Urgau:stabilize_trait_upcasting, r=WaffleLapkin

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Stabilize RFC3324 dyn upcasting coercion

This PR stabilize the `trait_upcasting` feature, aka https://github.com/rust-lang/rfcs/pull/3324.

The FCP was completed here: https://github.com/rust-lang/rust/issues/65991#issuecomment-1817552398.

~~And also remove the `deref_into_dyn_supertrait` lint which is now handled by dyn upcasting coercion.~~

Heavily inspired by https://github.com/rust-lang/rust/pull/101718
Fixes https://github.com/rust-lang/rust/issues/65991
This commit is contained in:
bors 2023-11-22 16:15:34 +00:00
commit 6d2b84b3ed
69 changed files with 107 additions and 357 deletions
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51
compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
View file

@ -9,13 +9,10 @@
use hir::def_id::DefId;
use hir::LangItem;
use rustc_hir as hir;
use rustc_infer::traits::ObligationCause;
use rustc_infer::traits::{Obligation, PolyTraitObligation, SelectionError};
use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
use rustc_middle::ty::{self, Ty, TypeVisitableExt};
use crate::traits;
use crate::traits::query::evaluate_obligation::InferCtxtExt;
use crate::traits::util;
use super::BuiltinImplConditions;
@ -690,45 +687,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
})
}
/// Temporary migration for #89190
fn need_migrate_deref_output_trait_object(
&mut self,
ty: Ty<'tcx>,
param_env: ty::ParamEnv<'tcx>,
cause: &ObligationCause<'tcx>,
) -> Option<ty::PolyExistentialTraitRef<'tcx>> {
let tcx = self.tcx();
if tcx.features().trait_upcasting {
return None;
}
// <ty as Deref>
let trait_ref = ty::TraitRef::new(tcx, tcx.lang_items().deref_trait()?, [ty]);
let obligation =
traits::Obligation::new(tcx, cause.clone(), param_env, ty::Binder::dummy(trait_ref));
if !self.infcx.predicate_may_hold(&obligation) {
return None;
}
self.infcx.probe(|_| {
let ty = traits::normalize_projection_type(
self,
param_env,
ty::AliasTy::new(tcx, tcx.lang_items().deref_target()?, trait_ref.args),
cause.clone(),
0,
// We're *intentionally* throwing these away,
// since we don't actually use them.
&mut vec![],
)
.ty()
.unwrap();
if let ty::Dynamic(data, ..) = ty.kind() { data.principal() } else { None }
})
}
/// Searches for unsizing that might apply to `obligation`.
fn assemble_candidates_for_unsizing(
&mut self,
@ -786,15 +744,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
let principal_a = a_data.principal().unwrap();
let target_trait_did = principal_def_id_b.unwrap();
let source_trait_ref = principal_a.with_self_ty(self.tcx(), source);
if let Some(deref_trait_ref) = self.need_migrate_deref_output_trait_object(
source,
obligation.param_env,
&obligation.cause,
) {
if deref_trait_ref.def_id() == target_trait_did {
return;
}
}
for (idx, upcast_trait_ref) in
util::supertraits(self.tcx(), source_trait_ref).enumerate()