Rollup merge of #122120 - fmease:sugg-assoc-ty-bound-on-eq-bound, r=compiler-errors
Suggest associated type bounds on problematic associated equality bounds Fixes #105056. TL;DR: Suggest `Trait<Ty: Bound>` on `Trait<Ty = Bound>` in Rust >=2021. ~~Blocked on #122055 (stabilization of `associated_type_bounds`), I'd say.~~ (merged)
This commit is contained in:
Matthias Krüger
GitHub
commit
ff8cdc9e14
10 changed files with 287 additions and 99 deletions
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@ -9,8 +9,85 @@ use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamNa
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use super::HirTyLowerer;
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impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
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/// Prohibit or lint against *bare* trait object types depending on the edition.
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///
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/// *Bare* trait object types are ones that aren't preceeded by the keyword `dyn`.
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/// In edition 2021 and onward we emit a hard error for them.
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pub(super) fn prohibit_or_lint_bare_trait_object_ty(
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&self,
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self_ty: &hir::Ty<'_>,
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in_path: bool,
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) {
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let tcx = self.tcx();
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let hir::TyKind::TraitObject([poly_trait_ref, ..], _, TraitObjectSyntax::None) =
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self_ty.kind
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else {
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return;
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};
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let needs_bracket = in_path
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&& !tcx
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.sess
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.source_map()
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.span_to_prev_source(self_ty.span)
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.ok()
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.is_some_and(|s| s.trim_end().ends_with('<'));
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let is_global = poly_trait_ref.trait_ref.path.is_global();
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let mut sugg = vec![(
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self_ty.span.shrink_to_lo(),
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format!(
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"{}dyn {}",
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if needs_bracket { "<" } else { "" },
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if is_global { "(" } else { "" },
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),
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)];
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if is_global || needs_bracket {
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sugg.push((
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self_ty.span.shrink_to_hi(),
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format!(
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"{}{}",
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if is_global { ")" } else { "" },
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if needs_bracket { ">" } else { "" },
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),
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));
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}
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if self_ty.span.edition().at_least_rust_2021() {
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let msg = "trait objects must include the `dyn` keyword";
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let label = "add `dyn` keyword before this trait";
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let mut diag =
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rustc_errors::struct_span_code_err!(tcx.dcx(), self_ty.span, E0782, "{}", msg);
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if self_ty.span.can_be_used_for_suggestions()
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&& !self.maybe_suggest_impl_trait(self_ty, &mut diag)
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{
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// FIXME: Only emit this suggestion if the trait is object safe.
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diag.multipart_suggestion_verbose(label, sugg, Applicability::MachineApplicable);
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}
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// Check if the impl trait that we are considering is an impl of a local trait.
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self.maybe_suggest_blanket_trait_impl(self_ty, &mut diag);
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self.maybe_suggest_assoc_ty_bound(self_ty, &mut diag);
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diag.stash(self_ty.span, StashKey::TraitMissingMethod);
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} else {
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let msg = "trait objects without an explicit `dyn` are deprecated";
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tcx.node_span_lint(BARE_TRAIT_OBJECTS, self_ty.hir_id, self_ty.span, msg, |lint| {
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if self_ty.span.can_be_used_for_suggestions() {
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lint.multipart_suggestion_verbose(
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"if this is an object-safe trait, use `dyn`",
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sugg,
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Applicability::MachineApplicable,
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);
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}
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self.maybe_suggest_blanket_trait_impl(self_ty, lint);
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});
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}
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}
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/// Make sure that we are in the condition to suggest the blanket implementation.
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pub(super) fn maybe_lint_blanket_trait_impl<G: EmissionGuarantee>(
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fn maybe_suggest_blanket_trait_impl<G: EmissionGuarantee>(
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&self,
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self_ty: &hir::Ty<'_>,
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diag: &mut Diag<'_, G>,
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@ -75,9 +152,11 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
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}
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/// Make sure that we are in the condition to suggest `impl Trait`.
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fn maybe_lint_impl_trait(&self, self_ty: &hir::Ty<'_>, diag: &mut Diag<'_>) -> bool {
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fn maybe_suggest_impl_trait(&self, self_ty: &hir::Ty<'_>, diag: &mut Diag<'_>) -> bool {
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let tcx = self.tcx();
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let parent_id = tcx.hir().get_parent_item(self_ty.hir_id).def_id;
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// FIXME: If `type_alias_impl_trait` is enabled, also look for `Trait0<Ty = Trait1>`
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// and suggest `Trait0<Ty = impl Trait1>`.
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let (sig, generics, owner) = match tcx.hir_node_by_def_id(parent_id) {
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hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(sig, generics, _), .. }) => {
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(sig, generics, None)
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@ -186,71 +265,37 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
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false
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}
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pub(super) fn maybe_lint_bare_trait(&self, self_ty: &hir::Ty<'_>, in_path: bool) {
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let tcx = self.tcx();
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if let hir::TyKind::TraitObject([poly_trait_ref, ..], _, TraitObjectSyntax::None) =
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self_ty.kind
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fn maybe_suggest_assoc_ty_bound(&self, self_ty: &hir::Ty<'_>, diag: &mut Diag<'_>) {
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let mut parents = self.tcx().hir().parent_iter(self_ty.hir_id);
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if let Some((_, hir::Node::TypeBinding(binding))) = parents.next()
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&& let hir::TypeBindingKind::Equality { term: hir::Term::Ty(obj_ty) } = binding.kind
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{
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let needs_bracket = in_path
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&& !tcx
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.sess
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.source_map()
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.span_to_prev_source(self_ty.span)
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.ok()
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.is_some_and(|s| s.trim_end().ends_with('<'));
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let is_global = poly_trait_ref.trait_ref.path.is_global();
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let mut sugg = Vec::from_iter([(
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self_ty.span.shrink_to_lo(),
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format!(
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"{}dyn {}",
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if needs_bracket { "<" } else { "" },
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if is_global { "(" } else { "" },
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),
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)]);
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if is_global || needs_bracket {
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sugg.push((
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self_ty.span.shrink_to_hi(),
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format!(
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"{}{}",
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if is_global { ")" } else { "" },
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if needs_bracket { ">" } else { "" },
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),
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));
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if let Some((_, hir::Node::TraitRef(..))) = parents.next()
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&& let Some((_, hir::Node::Ty(ty))) = parents.next()
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&& let hir::TyKind::TraitObject(..) = ty.kind
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{
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// Assoc ty bounds aren't permitted inside trait object types.
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return;
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}
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if self_ty.span.edition().at_least_rust_2021() {
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let msg = "trait objects must include the `dyn` keyword";
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let label = "add `dyn` keyword before this trait";
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let mut diag =
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rustc_errors::struct_span_code_err!(tcx.dcx(), self_ty.span, E0782, "{}", msg);
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if self_ty.span.can_be_used_for_suggestions()
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&& !self.maybe_lint_impl_trait(self_ty, &mut diag)
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{
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diag.multipart_suggestion_verbose(
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label,
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sugg,
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Applicability::MachineApplicable,
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);
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}
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// check if the impl trait that we are considering is a impl of a local trait
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self.maybe_lint_blanket_trait_impl(self_ty, &mut diag);
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diag.stash(self_ty.span, StashKey::TraitMissingMethod);
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let lo = if binding.gen_args.span_ext.is_dummy() {
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binding.ident.span
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} else {
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let msg = "trait objects without an explicit `dyn` are deprecated";
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tcx.node_span_lint(BARE_TRAIT_OBJECTS, self_ty.hir_id, self_ty.span, msg, |lint| {
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if self_ty.span.can_be_used_for_suggestions() {
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lint.multipart_suggestion_verbose(
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"if this is an object-safe trait, use `dyn`",
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sugg,
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Applicability::MachineApplicable,
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);
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}
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self.maybe_lint_blanket_trait_impl(self_ty, lint);
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});
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binding.gen_args.span_ext
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};
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let hi = obj_ty.span;
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if !lo.eq_ctxt(hi) {
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return;
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}
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diag.span_suggestion_verbose(
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lo.between(hi),
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"you might have meant to write a bound here",
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": ",
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Applicability::MaybeIncorrect,
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);
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}
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}
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}
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@ -2339,12 +2339,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
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)
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}
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hir::TyKind::TraitObject(bounds, lifetime, repr) => {
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self.maybe_lint_bare_trait(hir_ty, in_path);
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self.prohibit_or_lint_bare_trait_object_ty(hir_ty, in_path);
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let repr = match repr {
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TraitObjectSyntax::Dyn | TraitObjectSyntax::None => ty::Dyn,
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TraitObjectSyntax::DynStar => ty::DynStar,
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};
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self.lower_trait_object_ty(
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hir_ty.span,
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hir_ty.hir_id,
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