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Consider principal trait ref's auto-trait super-traits in dyn upcasting

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This commit is contained in:
Michael Goulet 2023-12-27 03:17:37 +00:00
parent fa9f77ff35
commit ec8e898193
4 changed files with 93 additions and 52 deletions
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95
compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
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@ -10,7 +10,7 @@ use std::ops::ControlFlow;
use hir::def_id::DefId;
use hir::LangItem;
use rustc_data_structures::fx::FxHashSet;
use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
use rustc_hir as hir;
use rustc_infer::traits::ObligationCause;
use rustc_infer::traits::{Obligation, PolyTraitObligation, SelectionError};
@ -968,52 +968,61 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
//
// We always perform upcasting coercions when we can because of reason
// #2 (region bounds).
let auto_traits_compatible = b_data
.auto_traits()
// All of a's auto traits need to be in b's auto traits.
.all(|b| a_data.auto_traits().any(|a| a == b));
if auto_traits_compatible {
let principal_def_id_a = a_data.principal_def_id();
let principal_def_id_b = b_data.principal_def_id();
if principal_def_id_a == principal_def_id_b {
// no cyclic
let principal_def_id_a = a_data.principal_def_id();
let principal_def_id_b = b_data.principal_def_id();
if principal_def_id_a == principal_def_id_b {
// We may upcast to auto traits that are either explicitly listed in
// the object type's bounds, or implied by the principal trait ref's
// supertraits.
let a_auto_traits: FxIndexSet<DefId> = a_data
.auto_traits()
.chain(principal_def_id_a.into_iter().flat_map(|principal_def_id| {
util::supertrait_def_ids(self.tcx(), principal_def_id)
.filter(|def_id| self.tcx().trait_is_auto(*def_id))
}))
.collect();
let auto_traits_compatible = b_data
.auto_traits()
// All of a's auto traits need to be in b's auto traits.
.all(|b| a_auto_traits.contains(&b));
if auto_traits_compatible {
candidates.vec.push(BuiltinUnsizeCandidate);
} else if principal_def_id_a.is_some() && principal_def_id_b.is_some() {
// not casual unsizing, now check whether this is trait upcasting coercion.
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;
}
}
} else if principal_def_id_a.is_some() && principal_def_id_b.is_some() {
// not casual unsizing, now check whether this is trait upcasting coercion.
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()
{
self.infcx.probe(|_| {
if upcast_trait_ref.def_id() == target_trait_did
&& let Ok(nested) = self.match_upcast_principal(
obligation,
upcast_trait_ref,
a_data,
b_data,
a_region,
b_region,
)
{
if nested.is_none() {
candidates.ambiguous = true;
}
candidates.vec.push(TraitUpcastingUnsizeCandidate(idx));
for (idx, upcast_trait_ref) in
util::supertraits(self.tcx(), source_trait_ref).enumerate()
{
self.infcx.probe(|_| {
if upcast_trait_ref.def_id() == target_trait_did
&& let Ok(nested) = self.match_upcast_principal(
obligation,
upcast_trait_ref,
a_data,
b_data,
a_region,
b_region,
)
{
if nested.is_none() {
candidates.ambiguous = true;
}
})
}
candidates.vec.push(TraitUpcastingUnsizeCandidate(idx));
}
})
}
}
}