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Descriptive error when users try to combine RPITIT/AFIT with specialization

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This commit is contained in:
Michael Goulet 2023-02-28 02:03:26 +00:00
parent 6290ae92b2
commit ecac8fd5af
7 changed files with 83 additions and 65 deletions
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30
compiler/rustc_metadata/src/rmeta/encoder.rs
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@ -1101,34 +1101,6 @@ fn should_encode_const(def_kind: DefKind) -> bool {
}
}
fn should_encode_trait_impl_trait_tys(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
if tcx.def_kind(def_id) != DefKind::AssocFn {
return false;
}
let Some(item) = tcx.opt_associated_item(def_id) else { return false; };
if item.container != ty::AssocItemContainer::ImplContainer {
return false;
}
let Some(trait_item_def_id) = item.trait_item_def_id else { return false; };
// FIXME(RPITIT): This does a somewhat manual walk through the signature
// of the trait fn to look for any RPITITs, but that's kinda doing a lot
// of work. We can probably remove this when we refactor RPITITs to be
// associated types.
tcx.fn_sig(trait_item_def_id).subst_identity().skip_binder().output().walk().any(|arg| {
if let ty::GenericArgKind::Type(ty) = arg.unpack()
&& let ty::Alias(ty::Projection, data) = ty.kind()
&& tcx.def_kind(data.def_id) == DefKind::ImplTraitPlaceholder
{
true
} else {
false
}
})
}
// Return `false` to avoid encoding impl trait in trait, while we don't use the query.
fn should_encode_fn_impl_trait_in_trait<'tcx>(_tcx: TyCtxt<'tcx>, _def_id: DefId) -> bool {
false
@ -1211,7 +1183,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
if let DefKind::Enum | DefKind::Struct | DefKind::Union = def_kind {
self.encode_info_for_adt(def_id);
}
if should_encode_trait_impl_trait_tys(tcx, def_id)
if tcx.impl_method_has_trait_impl_trait_tys(def_id)
&& let Ok(table) = self.tcx.collect_return_position_impl_trait_in_trait_tys(def_id)
{
record!(self.tables.trait_impl_trait_tys[def_id] <- table);