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Make GATs object safe under generic_associated_types_extended feature

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This commit is contained in:
Jack Huey 2022-03-13 11:56:18 -04:00
parent 0677edc86e
commit 52b00db235
19 changed files with 240 additions and 44 deletions
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22
compiler/rustc_trait_selection/src/traits/object_safety.rs
View file

@ -131,16 +131,18 @@ fn object_safety_violations_for_trait(
}),
);
violations.extend(
tcx.associated_items(trait_def_id)
.in_definition_order()
.filter(|item| item.kind == ty::AssocKind::Type)
.filter(|item| !tcx.generics_of(item.def_id).params.is_empty())
.map(|item| {
let ident = item.ident(tcx);
ObjectSafetyViolation::GAT(ident.name, ident.span)
}),
);
if !tcx.features().generic_associated_types_extended {
violations.extend(
tcx.associated_items(trait_def_id)
.in_definition_order()
.filter(|item| item.kind == ty::AssocKind::Type)
.filter(|item| !tcx.generics_of(item.def_id).params.is_empty())
.map(|item| {
let ident = item.ident(tcx);
ObjectSafetyViolation::GAT(ident.name, ident.span)
}),
);
}
debug!(
"object_safety_violations_for_trait(trait_def_id={:?}) = {:?}",

70
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
View file

@ -11,8 +11,8 @@ use rustc_hir::lang_items::LangItem;
use rustc_index::bit_set::GrowableBitSet;
use rustc_infer::infer::InferOk;
use rustc_infer::infer::LateBoundRegionConversionTime::HigherRankedType;
use rustc_middle::ty::subst::{GenericArg, GenericArgKind, Subst, SubstsRef};
use rustc_middle::ty::{self, Ty};
use rustc_middle::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, Subst, SubstsRef};
use rustc_middle::ty::{self, GenericParamDefKind, Ty};
use rustc_middle::ty::{ToPolyTraitRef, ToPredicate};
use rustc_span::def_id::DefId;
@ -487,18 +487,80 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
.collect();
for assoc_type in assoc_types {
if !tcx.generics_of(assoc_type).params.is_empty() {
let defs: &ty::Generics = tcx.generics_of(assoc_type);
if !defs.params.is_empty() && !tcx.features().generic_associated_types_extended {
tcx.sess.delay_span_bug(
obligation.cause.span,
"GATs in trait object shouldn't have been considered",
);
return Err(SelectionError::Unimplemented);
}
// This maybe belongs in wf, but that can't (doesn't) handle
// higher-ranked things.
// Prevent, e.g., `dyn Iterator<Item = str>`.
for bound in self.tcx().item_bounds(assoc_type) {
let subst_bound = bound.subst(tcx, trait_predicate.trait_ref.substs);
let subst_bound =
if defs.count() == 0 {
bound.subst(tcx, trait_predicate.trait_ref.substs)
} else {
let mut substs = smallvec::SmallVec::with_capacity(defs.count());
substs.extend(trait_predicate.trait_ref.substs.iter());
let mut bound_vars: smallvec::SmallVec<[ty::BoundVariableKind; 8]> =
smallvec::SmallVec::with_capacity(
bound.kind().bound_vars().len() + defs.count(),
);
bound_vars.extend(bound.kind().bound_vars().into_iter());
InternalSubsts::fill_single(&mut substs, defs, &mut |param, _| match param
.kind
{
GenericParamDefKind::Type { .. } => {
let kind = ty::BoundTyKind::Param(param.name);
let bound_var = ty::BoundVariableKind::Ty(kind);
bound_vars.push(bound_var);
tcx.mk_ty(ty::Bound(
ty::INNERMOST,
ty::BoundTy {
var: ty::BoundVar::from_usize(bound_vars.len() - 1),
kind,
},
))
.into()
}
GenericParamDefKind::Lifetime => {
let kind = ty::BoundRegionKind::BrNamed(param.def_id, param.name);
let bound_var = ty::BoundVariableKind::Region(kind);
bound_vars.push(bound_var);
tcx.mk_region(ty::ReLateBound(
ty::INNERMOST,
ty::BoundRegion {
var: ty::BoundVar::from_usize(bound_vars.len() - 1),
kind,
},
))
.into()
}
GenericParamDefKind::Const { .. } => {
let bound_var = ty::BoundVariableKind::Const;
bound_vars.push(bound_var);
tcx.mk_const(ty::ConstS {
ty: tcx.type_of(param.def_id),
val: ty::ConstKind::Bound(
ty::INNERMOST,
ty::BoundVar::from_usize(bound_vars.len() - 1),
),
})
.into()
}
});
let bound_vars = tcx.mk_bound_variable_kinds(bound_vars.into_iter());
let assoc_ty_substs = tcx.intern_substs(&substs);
let bound_vars = tcx.mk_bound_variable_kinds(bound_vars.into_iter());
let bound = bound.kind().skip_binder().subst(tcx, assoc_ty_substs);
tcx.mk_predicate(ty::Binder::bind_with_vars(bound, bound_vars))
};
let normalized_bound = normalize_with_depth_to(
self,
obligation.param_env,