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Suggest relaxing implicit type Assoc: Sized; bound

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Fix #85378.
This commit is contained in:
Esteban Küber 2023-10-18 22:54:35 +00:00
parent 93e62a260f
commit e8d4fb8aaa
5 changed files with 67 additions and 0 deletions
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23
compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
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@ -2652,6 +2652,29 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
// Check for foreign traits being reachable.
self.tcx.visible_parent_map(()).get(&def_id).is_some()
};
if Some(def_id) == self.tcx.lang_items().sized_trait()
&& let Some(hir::Node::TraitItem(hir::TraitItem {
ident,
kind: hir::TraitItemKind::Type(bounds, None),
..
})) = tcx.hir().get_if_local(item_def_id)
// Do not suggest relaxing if there is an explicit `Sized` obligation.
&& !bounds.iter()
.filter_map(|bound| bound.trait_ref())
.any(|tr| tr.trait_def_id() == self.tcx.lang_items().sized_trait())
{
let (span, separator) = if let [.., last] = bounds {
(last.span().shrink_to_hi(), " +")
} else {
(ident.span.shrink_to_hi(), ":")
};
err.span_suggestion_verbose(
span,
"consider relaxing the implicit `Sized` restriction",
format!("{separator} ?Sized"),
Applicability::MachineApplicable,
);
}
if let DefKind::Trait = tcx.def_kind(item_def_id)
&& !visible_item
{