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use more descriptive names
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@ -908,111 +908,113 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
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let param_env = obligation.param_env;
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// Try to apply the original trait binding obligation by borrowing.
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let mut try_borrowing = |old_pred: ty::PolyTraitPredicate<'tcx>,
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blacklist: &[DefId]|
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-> bool {
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if blacklist.contains(&old_pred.def_id()) {
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return false;
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}
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// We map bounds to `&T` and `&mut T`
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let trait_pred_and_imm_ref = old_pred.map_bound(|trait_pred| {
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(
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trait_pred,
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self.tcx.mk_imm_ref(self.tcx.lifetimes.re_static, trait_pred.self_ty()),
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)
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});
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let trait_pred_and_mut_ref = old_pred.map_bound(|trait_pred| {
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(
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trait_pred,
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self.tcx.mk_mut_ref(self.tcx.lifetimes.re_static, trait_pred.self_ty()),
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)
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});
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let mut try_borrowing =
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|old_pred: ty::PolyTraitPredicate<'tcx>, blacklist: &[DefId]| -> bool {
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if blacklist.contains(&old_pred.def_id()) {
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return false;
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}
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// We map bounds to `&T` and `&mut T`
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let trait_pred_and_imm_ref = old_pred.map_bound(|trait_pred| {
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(
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trait_pred,
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self.tcx.mk_imm_ref(self.tcx.lifetimes.re_static, trait_pred.self_ty()),
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)
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});
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let trait_pred_and_mut_ref = old_pred.map_bound(|trait_pred| {
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(
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trait_pred,
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self.tcx.mk_mut_ref(self.tcx.lifetimes.re_static, trait_pred.self_ty()),
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)
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});
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let mk_result = |trait_pred_and_new_ty| {
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let obligation =
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self.mk_trait_obligation_with_new_self_ty(param_env, trait_pred_and_new_ty);
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self.predicate_must_hold_modulo_regions(&obligation)
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};
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let imm_result = mk_result(trait_pred_and_imm_ref);
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let mut_result = mk_result(trait_pred_and_mut_ref);
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let mk_result = |trait_pred_and_new_ty| {
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let obligation =
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self.mk_trait_obligation_with_new_self_ty(param_env, trait_pred_and_new_ty);
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self.predicate_must_hold_modulo_regions(&obligation)
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};
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let imm_ref_self_ty_satisfies_pred = mk_result(trait_pred_and_imm_ref);
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let mut_ref_self_ty_satisfies_pred = mk_result(trait_pred_and_mut_ref);
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let ref_inner_ty_result =
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let (ref_inner_ty_satisfies_pred, ref_inner_ty_mut) =
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if let ObligationCauseCode::ItemObligation(_) = obligation.cause.code()
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&& let ty::Ref(_, ty, mutability) = old_pred.self_ty().skip_binder().kind()
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{
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Some((mk_result(old_pred.map_bound(|trait_pred| (trait_pred, *ty))), mutability))
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(
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mk_result(old_pred.map_bound(|trait_pred| (trait_pred, *ty))),
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matches!(mutability, hir::Mutability::Mut),
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)
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} else {
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None
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(false, false)
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};
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if imm_result || mut_result || ref_inner_ty_result.map_or(false, |(result, _)| result) {
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if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
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// We have a very specific type of error, where just borrowing this argument
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// might solve the problem. In cases like this, the important part is the
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// original type obligation, not the last one that failed, which is arbitrary.
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// Because of this, we modify the error to refer to the original obligation and
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// return early in the caller.
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if imm_ref_self_ty_satisfies_pred
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|| mut_ref_self_ty_satisfies_pred
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|| ref_inner_ty_satisfies_pred
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{
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if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
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// We have a very specific type of error, where just borrowing this argument
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// might solve the problem. In cases like this, the important part is the
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// original type obligation, not the last one that failed, which is arbitrary.
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// Because of this, we modify the error to refer to the original obligation and
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// return early in the caller.
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let msg = format!("the trait bound `{}` is not satisfied", old_pred);
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if has_custom_message {
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err.note(&msg);
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} else {
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err.message =
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vec![(rustc_errors::DiagnosticMessage::Str(msg), Style::NoStyle)];
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}
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if snippet.starts_with('&') {
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// This is already a literal borrow and the obligation is failing
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// somewhere else in the obligation chain. Do not suggest non-sense.
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return false;
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}
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err.span_label(
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span,
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&format!(
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"expected an implementor of trait `{}`",
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old_pred.print_modifiers_and_trait_path(),
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),
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);
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// This if is to prevent a special edge-case
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if matches!(
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span.ctxt().outer_expn_data().kind,
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ExpnKind::Root | ExpnKind::Desugaring(DesugaringKind::ForLoop)
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) {
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// We don't want a borrowing suggestion on the fields in structs,
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// ```
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// struct Foo {
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// the_foos: Vec<Foo>
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// }
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// ```
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if imm_result && mut_result {
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err.span_suggestions(
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span.shrink_to_lo(),
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"consider borrowing here",
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["&".to_string(), "&mut ".to_string()].into_iter(),
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Applicability::MaybeIncorrect,
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);
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let msg = format!("the trait bound `{}` is not satisfied", old_pred);
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if has_custom_message {
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err.note(&msg);
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} else {
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let is_mut = mut_result
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|| ref_inner_ty_result.map_or(false, |(_, mutabl)| {
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matches!(mutabl, hir::Mutability::Mut)
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});
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err.span_suggestion_verbose(
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span.shrink_to_lo(),
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&format!(
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"consider{} borrowing here",
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if is_mut { " mutably" } else { "" }
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),
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format!("&{}", if is_mut { "mut " } else { "" }),
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Applicability::MaybeIncorrect,
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);
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err.message =
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vec![(rustc_errors::DiagnosticMessage::Str(msg), Style::NoStyle)];
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}
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if snippet.starts_with('&') {
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// This is already a literal borrow and the obligation is failing
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// somewhere else in the obligation chain. Do not suggest non-sense.
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return false;
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}
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err.span_label(
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span,
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&format!(
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"expected an implementor of trait `{}`",
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old_pred.print_modifiers_and_trait_path(),
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),
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);
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// This if is to prevent a special edge-case
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if matches!(
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span.ctxt().outer_expn_data().kind,
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ExpnKind::Root | ExpnKind::Desugaring(DesugaringKind::ForLoop)
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) {
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// We don't want a borrowing suggestion on the fields in structs,
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// ```
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// struct Foo {
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// the_foos: Vec<Foo>
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// }
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// ```
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if imm_ref_self_ty_satisfies_pred && mut_ref_self_ty_satisfies_pred {
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err.span_suggestions(
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span.shrink_to_lo(),
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"consider borrowing here",
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["&".to_string(), "&mut ".to_string()].into_iter(),
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Applicability::MaybeIncorrect,
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);
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} else {
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let is_mut = mut_ref_self_ty_satisfies_pred || ref_inner_ty_mut;
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err.span_suggestion_verbose(
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span.shrink_to_lo(),
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&format!(
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"consider{} borrowing here",
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if is_mut { " mutably" } else { "" }
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),
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format!("&{}", if is_mut { "mut " } else { "" }),
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Applicability::MaybeIncorrect,
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);
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}
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}
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return true;
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}
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return true;
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}
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}
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return false;
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};
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return false;
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};
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if let ObligationCauseCode::ImplDerivedObligation(cause) = &*code {
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try_borrowing(cause.derived.parent_trait_pred, &[])
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